The Pennsylvania State University

The Graduate School

Eberly College of Science

COMMUNITY STRUCTURE OF HYDROTHERMAL VENTS AT THE

EASTERN-LAU SPREADING CENTER

A Thesis in

Biology

by

Kevin A. Zelnio

© 2009 Kevin A. Zelnio

Submitted in Partial Fulfillment of the Requirements for the Degree of

Master of Science

August 2009

ii The thesis of Kevin A. Zelnio was reviewed and approved* by the following:

Charles R. Fisher Professor of Biology and Assistant Department for Graduate Education Thesis Advisor

Stephen W. Schaeffer Associate Professor of Biology

Jay R. Stauffer, Jr. Distinguished Professor of Ichthyology

Douglas Cavener Professor of Biology Head of the Department of Biology

*Signatures are on file in the Graduate School

iii ABSTRACT

Deep sea hydrothermal vents form at plate boundaries and volcanic hotspots. Cold seawater seeping through fissures in the seafloor comes into contact with superheated rock above the magma chamber. The heated seawater rises carrying dissolved metals and sulfides that precipitate out of solution when it comes into contact with the cold water at seafloor’s surface, forming chimney-like structures. The Eastern-Lau Spreading Center (ELSC) in the

Lau back-arc basin contains dense aggregations of chemoautotrophic macrofauna including two snails, Alviniconcha hessleri and Ifremeria nautilei, and the mussel, Bathymodiolus brevior. Each chemoautotrophic macrofaunal species occupies a defined thermo-chemical range. Alviniconcha hessleri is found in areas closest to the hydrothermal source where oxygen levels are lower, temperature is higher and sulfide concentrations are higher, whereas

B. brevior occupies a microhabitat closer to the other end of the thermo-chemical spectrum.

Ifremeria nautilei occupies a thermo-chemical tolerance range overlapping the upper and lower distributions of B. brevior and A. hessleri, respectively. In this study, 36 quantitative community samples from each of the chemoautotrophic macrofauna were collected from 4 sites with depths ranging from 1700 m in the south to 2800 m in the north. In general, communities associated with A. hessleri were lower in abundance and higher in Shannon diversity index and Pielou’s evenness index, yet had fewer numbers of species. Though Bray-

Curtis similarity between I. nautilei and B. brevior hosted communities was significantly different (ANOSIM, Global R=0.82, P=0.02; Chapter 3: Table 6) there was a qualitative trend of higher abundance and biomass and lower Shannon diversity index, Pielous’s evenness index and mean number of species in collections of B. brevior relative to I. nautilei collections. There were distinct groups (ANOSIM: Global R=0.51, P=0.001; Chapter 3: see iv Table 6 for pairwise comparisons and Figure 6 for multidimensional scaling plot) of each community type in multi-dimensional space based on Bray-Curtis similarity. When grouped by study site, communities from southernmost Tu’i Malila had significantly higher Shannon diversity index, Pielou’s evenness index and mean number of species than the northernmost locality, Kilo Moana. In multi-dimensional space, only Tu’i Malila formed a distinct non- overlapping group based on Bray-Curtis Similarity while the two northern sites, Kilo Moana and TowCam, formed a distinct group and collections from ABE were interspersed.

This thesis also contains taxonomic work on a new species of caridean shrimp

(Chapter 1) and the hexacorallian fauna of the ELSC hydrothermal vents (Chapter 2). The new species of shrimp is in the family Alvinicarididae and genus Alvinocaris, a taxon specialized to deep-sea chemosynthetic ecosystems. A combination of morphological characters set it apart from known described species. Autapomorphies included a well- defined mesial notch in the telson and 2 rows of accessory spinules on the third to fifth pereopods. Analysis of the mitochondrial COI gene supports its position as a new species and confirms similar patterns within the family Alvinocarididae as found in previous molecular studies. A key to family Alvinocarididae is included. Additionally, 4 species of anemone, from the vicinity of hydrothermal vents at ELSC are described based on morphology. They are put into the genera Cyananthea, Alvinactis (Actinoscyphiidae), Chondrophellia

(Hormathiidae) and Sagartiogeton (Sagartiidae). Two additional morphotypes from the families Actinostolidae and Hormatiidae could not be further identified based on existing material but contain notes on their morphology and distribution. The morphology and distribution of the first record of an abundant zoanthid from a hydrothermal vent is also noted, but not described. v TABLE OF CONTENTS

List of Figures...... vii

List of Tables...... xiii

Acknowledgments...... xvi

Introduction...... 1

Chapter 1 A new species of Alvinocaris (Crustacea: Decapoda: Alvinocarididae) from

hydrothermal vents at the East-Lau Spreading Center, Western Pacific...... 10

Abstract...... 10

Introduction...... 10

Materials and Methods...... 11

Taxonomic Results...... 14

Ecology...... 26

Molecular Phylogeny...... 30

Discussion...... 32

Key to the Family Alvinocarididae...... 37

Acknowledgments...... 42

Literature Cited...... 42

Chapter 2 Hexacorals (Anthozoa: Actiniaria, Zoanthidea) from hydrothermal vents in the

South-western Pacific...... 50

Abstract...... 50

Introduction...... 50

Materials and Methods...... 53

Results and Discussion...... 54 vi Other Hexacorallia...... 92

Ecological Observations...... 96

Acknowledgments...... 100

Literature Cited...... 100

Chapter 3 Community Structure of Hydrothermal Vent Communities at the East-Lau

Spreading Center, Southwest Pacific...... 107

Abstract...... 107

Introduction...... 108

Materials and Methods...... 110

Results...... 117

Discussion...... 130

Conclusions...... 138

Acknowledgments...... 139

Literature Cited...... 140

Chapter 4 Biogeography of the Eastern-Lau Spreading Center...... 149

Literature Cited...... 154

Appendix 1...... 158

vii LIST OF FIGURES

Figure 1-1: Map of collection sites at the Lau Basin with topographic features.

Background image is courtesy of the Ridge Multibeam Synthesis Data Portal of the

Marine Geoscience Data System...... 12

Figure 1-2: Figure 2: Alvinocaris komaii, new species, holotype female (a-d) and

paratype female (e). a) whole specimen, right lateral view; b) rostrum, left lateral

view; c) antennular peduncles, dorsal view; d) telson and uropods, dorsal view; e)

close-up of posterior margin of paratype telson showing occasional plumose setae.

Scale bar = 5 mm (a) or 2 mm (b-e)...... 16

Figure 1-3: Alvinocaris komaii, new species, holotype female (a-l). a) mandible, interior

view; b) mandible, exterior view; c) first maxilla, exterior view; d) first maxilla

close-up of teeth on distolateral margin of proximal endite; e) second maxilla,

interior view; f) second maxilla, interior view; g) close-up view of second maxilla

endites and palp, exterior view; g) first maxilliped, exterior view; h) first maxilliped,

interior view; i) second maxilliped, interior view; j) second maxilliped with palp,

setae removed, exterior view; k) third maxilliped, ventral view; l) third maxilliped,

dorsolateral view. Scale bars = 0.5 mm...... 19

Figure 1-4: Alvinocaris komaii, new species, holotype female (a-g) and paratype male

(h). a) left first pereopod, external view; b) left second pereopod, external view; c)

left third pereopod, external view; d) left third pereopod dactylus and carpus, lateral

view; e) right fourth pereopod, inner view; f) left fifth pereopod, external view; g)

right first pleopod, inner view; h) appendix masculina. Scale bars = 1 mm...... 22 viii Figure 1-5: Alvinocaris komaii, new species, holotype female (a, c) and paratype male (b,

d). Variation in third pereopod, ventral view (a, b) and chelae of first pereopod (c, d).

Scale bars = 1 mm...... 23

Figure 1-6: In-situ photographs of Alvinocaris komaii from the ABE site. a) Several A.

komaii on top of the mussel Bathymodiolus brevior on a chimney wall. b) Closer

view on B. brevior (note the presence of the limpet Lepetodrilus schrolli and

barnacle Eochionelasmus ohtai on shells). Other alvinocaridids, either Nautilocaris

saintlaurentae or Chorocaris vandoverae are present on the right side of the photo

on the bare substrate. c) On bare substrate, note the gastropod Ifremeria nautilei

below and the barnacles E. ohtai to the left on the bare substrate...... 29

Figure 1-7: Phylogenetic tree of the Alvinocarididae based on a 600-bp alignment of the

partial COI sequence. Lebbeus carinatus was used as an outgroup. All GenBank

accession numbers appear after the species names. Bootstrap values are given for the

branches. The arrow points at the position of the new species...... 30-31

Figure 2-1: Map of collection sites at the Lau Basin with topographic features, see text

for details. Background image is courtesy of the Ridge Multibeam Synthesis Data

Portal of the Marine Geoscience Data System...... 52

Figure 2-2: Cyananthea hourdezi n. sp. External anatomy: A, and B, preserved

specimens; C, detail of distal row of cinclides; D, Living specimens; E, expanded

living specimen. Scale bars: A, B, 20 mm; C, 1 mm; E, 40 mm...... 56

Figure 2-3: Cyananthea hourdezi n. sp. Internal anatomy: A, longitudinal section through

distal column, showing mesogleal marginal sphincter (between arrows); B, cross

section of the mesenteries at actinopharynx, showing mesenteries from first to fourth ix cycle (numbers indicate the different cycles); C, detail of the marginal sphincter

muscles fibers embedded in the mesoglea; D, cross section thorough mesenteries

below actinopharynx showing diffuse retractor muscles; E, longitudinal section

through distal column showing a cinclide; F, cross section through a tentacle

showing longitudinal ectodermal muscles; G; cross section of the pedal disc showing

basilar muscles (arrows). Scale bars: A, 0.5 mm; B, 1 mm; C, 0.1 mm; D, 1 mm; E,

0.5 mm; F, 0.05 mm; G, 0.02 mm……………………………………………… 57-58

Figure 2-4: Cyananthea hourdezi n. sp. Cnidae: A, basitrich; B, basitrich; C, microbasic

p-mastigophore; D, basitrich; E, microbasic p-mastigophore; F; robust spirocyst; G,

basitrich; H, microbasic p-mastigophore; I, holotrich; J, basitrich; K, microbasic p-

mastigophore; L, basitrich; M, microbasic p-mastigophore...... 59-60

Figure 2-5: Alvinactis chessi n. sp. External anatomy: A, lateral view of living specimen;

B, oral view of living specimen; C, lateral view of living specimen; D, living

specimen in being collected; E, lateral view of preserved specimen; F, detail of the

distal perforated papillae (white arrows) and marginal ring (black arrow); G, detail

of the marginal ring and cycles of tentacles; H, detail of a missing tentacle

suggesting autotomy; I, detail of the distal perforated papillae (black arrow). Scale

bars; A, B, C, D, 100 mm; E, 30 mm; F, 5 mm; G, H, 2 mm; I, 3 mm……………. 66

Figure 2-6: Alvinactis chessi n. sp. Internal anatomy: A, cross section of the mesenteries

at actinopharynx, showing diffuse retractor muscles; B, longitudinal section through

distal column, showing mesogleal marginal sphincter and a perforated solid papilla

(arrow); C, cross section of the mesenteries below actinopharynx, showing

parietobasilar muscles (arrow); D, cross section through a tentacle showing x longitudinal ectodermal muscles; E, cross section of the pedal disc showing basilar

muscles; F, and G, longitudinal section through distal column showing a perforated

papillae. Scale bars: A, 1 mm; B, 2 mm; C, D, E, 0.1 mm; F, G, 1 mm……… 67-68

Figure 2-7: Alvinactis chessi n. sp. Cnidae: A, basitrich; B, holotrich; C, basitrich; D,

microbasic p-mastigophore; E, holotrich; F, robust spirocyst; G, basitrich; H,

holotrich; I, microbasic p-mastigophore; J, basitrich; K, microbasic p-mastigophore

1; L, microbasic p-mastigophore 2…………………………………………..… 69-70

Figure 2-8: Chondrophellia orangina n. sp. External anatomy: A, expanded living

specimen; B, lateral view of preserved specimen; C, oral view of preserved

specimen, showing notice the scapulus (arrows); D, expanded living specimen.

Scale bars: A, D, 100 mm; B, 20 mm; C, 20 mm...... 75

Figure 2-9: Chondrophellia orangina n. sp. Internal anatomy: A, cross section of the

mesenteries below actinopharynx, showing diffuse retractor muscles and abundant

ova; B, cross section of the mesenteries below actinopharynx, showing parietobasilar

muscles; C, longitudinal section through distal column, showing mesogleal marginal

sphincter (arrows); D, detail of the marginal sphincter muscles fibers embedded in

the mesoglea; E, cross section through a tentacle showing longitudinal ectodermal

muscles; F, cross section of the pedal disc showing basilar muscles (arrows). Scale

bars: A, 1 mm; B, 0.2 mm; C, 4 mm; D, E, 0.1 mm; F, 0.2 mm……………… 76-77

Figure 2-10: Chondrophellia orangina n. sp. Cnidae: A, basitrich 1; B, basitrich 2; C,

microbasic p-mastigophore; D, basitrich 1; E, basitrich 2; F, microbasic p-

mastigophore; G, basitrich 1; H, basitrich 2; I, microbasic p-mastigophore; J, robust

spirocyst; K, basitrich 1; L, basitrich 2; M, basitrich 1; N, basitrich 2; O, microbasic xi p-mastigophore; P, basitrich 1; Q, microbasic p-mastigophore; R, basitrich 1; S,

basitrich 2……………………………………………………………………… 79-80

Figure 2-11: Sagartiogeton erythraios n. sp. External anatomy: A, expanded living

specimen; B, lateral view of contracted, and preserved specimen; C, lateral-oral view

of preserved specimen, notice showing the acontia (arrow); D, detail of a cuticulate

tenaculum on the scapus, notice stratified cuticle. Scale bars: A, 50 mm; B, 10 mm;

C, 10 mm; D, 0.05 mm...... 84

Figure 2-12: Sagartiogeton erythraios n. sp. Internal anatomy: A, longitudinal section

through distal column, showing mesogleal marginal sphincter; B, cross section of the

directive mesenteries attached to the siphonoglyph (arrow), showing diffuse retractor

muscles; C, cross section through a tentacle showing longitudinal ectodermal

muscles; D, cross section of the pedal disc showing basilar muscles; E, cross section

of the mesenteries proximally, showing differentiated parietobasilar muscles

differentiated (arrow). Scale bars: A, B, 1 mm; C, D, 0.1 mm; E, 1 mm…….. 85-86

Figure 2-13: Sagartiogeton erythraios n. sp. Cnidae: A, basitrich; B, basitrich 1; C,

basitrich 1; D, microbasic p-mastigophore; E, gracile spirocyst; F, robust spirocyst;

G, basitrich 1; H, basitrich 2; I, microbasic p-mastigophore; J, basitrich 1; K,

microbasic p-mastigophore; L, basitrich 1; M, microbasic p-mastigophore 1; N,

microbasic p-mastigophore 2; O, basitrich 1; P, basitrich 2; Q, microbasic p-

mastigophore. Scale bar: Q, 50 µm...... 87-88

Figure 2-14: Other Hexacorallia. A, Actinostolidae sp., preserved and contracted

specimen; B, Actinostolidae sp. in situ on sulfide; C, Zoanthidea sp., preserved

specimens on basalt; D, Zoanthidea sp. in situ on basalt; E, Amphianthus sp. xii preserved and contracted specimens, notice including the small specimens generated

clonally through pedal laceration; F, Amphianthus sp. in situ on basalt; G, contracted

specimens of Amphianthus sp. on basalt in situ. Scale bars: A-G, 10 mm...... 93

Figure 3-1: Topographic map of the Lau Basin with collection sites indicated courtesy of

the Ridge Multibeam Synthesis Data Portal of the Marine Geoscience Data

System...... 111

Figure 3-2: Schematic diagram of the “mussel/snail pot” collection device. Drawing

provided by G. Telesnicki...... 112

Figure 3-3: Sampling effort curves among a) sites and b) foundation fauna types...... 118

Figure 3-4: Rarefaction curves showing number of species per number of individuals

among a) sites and b) foundation fauna types...... 127

Figure 3-5: Non-metric multidimensional scaling plot showing the similarity of

composition among samples of communities associated with Alviniconcha sp.,

Ifremeria nautilei, and Bathymodiolus brevior. Distance between samples is based on

Bray-Curtis similarity coefficients. Shapes designate foundation fauna type and

coloring represents sites...... 135

Figure 4-1: Dendrogram based on hierarchical clustering (group-average linking) of 78

genera found at ELSC. Similarity is based on Bray-Curtis coefficients. Abbreviations

are the same as in Appendix 1...... 151

xiii LIST OF TABLES

Table 1-1: Ratios of rostrum length to carapace length (RL/CL), antennular peduncular

segment 1 length to segment 3 length (AP1/AP3), and pereopod 1 palm width to

height (Palm W/H) for Alvinocaris komaii sp nov from three sites at the Eastern-Lau

Spreading Centre...... 26

Table 1-2: Characters of Alvinocaris spp. from the Pacific Ocean. l=length, w=width,

h=height...... 36

Table 2-1: Summary of size ranges of cnidae of Cyananthea hourdezi n. sp. x¯ : mean

length by mean width of capsules. SD: standard deviation. S: ratio of number of

specimens in which each type was found to number of specimens examined. N: total

number of capsules measured. F: frequency: +++ = very common, ++ = common, +

= less common, --- = sporadic...... 61

Table 2-2: Summary of size ranges of the cnidae of Alvinactis chessi n. sp. x¯ : mean

length by mean width of capsules. SD: standard deviation. S: ratio of number of

specimens in which each type was found to number of specimens examined. N: total

number of capsules measured. F: frequency: +++ = very common, ++ = common, +

= less common, --- = sporadic...... 71

Table 2-3: Summary of size ranges of the cnidae of Chondrophellia orangina n. sp. x¯ :

mean length by mean width of capsules. SD: standard deviation. S: ratio of number

of specimens in which each type was found to number of specimens examined. N:

total number of capsules measured. F: frequency: +++ = very common, ++ =

common, + = less common, --- = sporadic. nd: no data...... 81 xiv Table 2-4: Summary of size ranges of the cnidae of Chondrophellia orangina n. sp. x¯ :

mean length by mean width of capsules. SD: standard deviation. S: ratio of number

of specimens in which each type was found to number of specimens examined. N:

total number of capsules measured. F: frequency: +++ = very common, ++ =

common, + = less common, --- = sporadic. nd: no data...... 89

Table 2-5: Comparison between Sagartiogeton erythraios n. sp., other species of

Sagartiogeton from the deep-sea, and Kadosactis antarctica (Carlgren, 1928) from

the Southern Hemisphere. Data from original descriptions, Carlgren (1942), and

Rodríguez and López-González (2005)...... 91

Table 2-6: Summary of size ranges of the cnidae of Amphianthus sp. x¯ : mean length by

mean width of capsules. SD: standard deviation. S: ratio of number of specimens in

which each type was found to number of specimens examined. N: total number of

capsules measured. F: frequency: +++ = very common, ++ = common, + = less

common, --- = sporadic. nd = no data...... 95

Table 2-7: Hexacorallia from chemosynthetic environments...... 99

Table 3-1: Mean abundance within site or foundation fauna type collected in mussel/snail

pots. Bolded rows are the chemoautotrophic foundation fauna. ‘P’ denotes

presence...... 119-120

Table 3-2: Abundance and biomass of foundation fauna or associated fauna at each site or

foundation fauna type. Significance is determined by one-way ANOVA with P <

0.05...... 121

Table 3-3: Cumulative biomass of species in collections at each study site...... 123 xv Table 3-4: Cumulative biomass of species in collections of each foundation fauna

type...... 123

Table 3-5: Results of ANOSIM using species biomasses or species abundances among

sites. No sites were significantly different from another, therefore statistical results

are not shown...... 125

Table 3-6: Results of ANOSIM using species’ biomasses and species’ abundances among

foundation fauna types...... 126

Table 3-7: Diversity indices among site or among foundation fauna types. Significance is

determined by one-way ANOVA with P < 0.05...... 128

xvi ACKNOWLEDGEMENTS

The content of this thesis would not be possible without the skill and dedication of the captains and crews of the R/V Melville during the 2005 and 2006 expeditions and

ROV Jason II expedition leader and team. My wife, Linda, and two children, Elliot and

Freya, provided a constant source of inspiration and motivation. I thank my parents for inspiring me to follow my dreams and their emotional and financial support. I thank my advisor, Dr. Charles Fisher, for giving me an opportunity to do fascinating research. Dr.

Stephane Hourdez, Dr. Estefania Rodríguez and Dr. Marymegan Daly provided excellent mentorship in systematics. I thank the members of the Fisher Lab past and present for their support and stimulating conversations over the years. Guy Telesnicki provided much appreciated technical expertise. Rob Vohden, Jean Roth, Lara Miles, Molly Steele,

Nicole Iacheii, Benjamin Predmore and Mike McGinley provided help on various aspects of my research as undergraduate research assistants. This research was funded by NSF

Grant OCE 003403953 to Charles Fisher, a Training Award for New Investigators

(TAWNI) from the Census of Marine Life’s Biogeography of Chemosynthetic

Ecosystems project to Kevin Zelnio, the Cnidarian Tree of Life project to Marymegan

Daly, and the Pennsylvania State University. The background bathymetric image used in

Figs. 1-1, 2-1 and 3-1 is used with permission by the Ridge Multibeam Synthesis Data

Portal of the Marine Geoscience Data System. 1 INTRODUCTION

Prior to several oceanographic expeditions in the late 19th century, the deep sea was considered to have very few life forms able to persist in the aphotic, seemingly nutrient poor, waters (De La Beche 1834, Gage & Tyler 1992, Page 1856). Edward

Forbes, who put forth the azoic theory of the deep sea, wrote that “[t]he number of species and of individuals diminishes as we descend, pointing to a zero in the distribution of animal life as yet unvisited” (Forbes 1844, pg 167). Though the azoic theory wasn’t considered unsupported until after the HMS Challenger expedition of the 1870s, there was evidence of animals found upon soundings and underwater cables in the North

Atlantic Ocean as early as 1818. Unfortunately, these observations were often dismissed by most of the scientific community at the time based upon sampling methodology or upon reputation of the scientists (Anderson & Rice 2006).

The discovery of abundant communities surrounding hydrothermal vents in 1977

(Corliss et al. 1979) presented an entirely different possibility of food resources for deep sea inhabitants. Energy was derived chemically, not photosynthetically, by bacteria often in symbioses with metazoans (Nelson & Fisher 1995). Additionally, carbon and nitrogen stable isotope values of the vent fauna identified chemoautotrophy as the foundation of the hydrothermal vent food web (Fisher et al. 1994, Rau 1981, Rau & Hedges 1979).

Rapid growth in vent invertebrates with chemoautotrophic endosymbionts (Lutz et al.

1994, Rhoads et al. 1981) and high bacterial primary production support an enormous standing-stock biomass relative to the abyssal deep seafloor (Fisher 1996). Subsequently, chemosynthetic-based ecosystems were discovered at hydrocarbon seeps (Kennicutt II et al. 1985) and surrounding whale falls (Smith et al. 1989). In each of these habitats, 2 abundant and diverse communities of unique metazoans have been documented and described (Desbruyères et al. 2006, Van Dover et al. 2002).

Geology, vent fluid chemistry, and tectonic setting play an essential role in the ecology of hydrothermal vent ecosystems (Luther III et al. 2001, Tunnicliffe & Fowler

1996, Van Dover 1995). Vent plume incidence can vary with spreading rate (Baker et al.

1996). Ridge morphology and spreading rate can also influence community structure

(Van Dover 1995). The more hydrothermal vents that exist on a ridge segment, the greater the chance a given species can colonize new habitat (Tunnicliffe et al. 1997).

Vent fluid chemistry varies among hydrothermal mounds within a ridge segment (Ferrini et al. 2008, Le Bris et al. 2003, Von Damm 1990), as well as among ridge segments (Von

Damm 1990) and ridge systems. This variation can drive differences in faunal distributions (Henry et al. 2008, Johnson et al. 1988, Podowski et al. 2009, Sarrazin et al.

1999, Waite et al 2008).

The work presented in this thesis was conducted at the Eastern-Lau Spreading

Center (ELSC), situated in the Lau back-arc basin in the exclusive economic zone of the

Kingdom of Tonga, southwest Pacific Ocean. Back-arc basins result from a complex plate tectonics setting where two or more oceanic plates converge with one plate subducting beneath another. The friction caused by the subducting of the lower plate melts the rock along the plate boundary causing a volcanic arc to form on the overlaying plate. On the backside of that arc, a spreading centre was created as a result of the extensional forces of the subduction. Where back-arc spreading occurs, the crust is thin and fragile (Sdrolias & Müller 2006). Seawater seeps down through cracks and fissures and comes into contact with super-heated rock. The heated seawater rises carrying 3 reduced chemicals and heavy metals that exit the crust at the seafloor where the reduced chemicals and metals precipitate out of solution creating hydrothermal vent chimneys.

The aim of this thesis was two-fold. The first aim was to describe and characterize some of the fauna associated with of the ELSC vent community. This task required careful identification of the species that inhabit the vent community. The deep sea is a very species-rich environment with estimates ranging from 500,000 to 10,000,000 species (Snelgrove & Smith 2002). New species are constantly being described and it is no surprise to encounter more than one species new to science on any given deep sea expedition. In the course of my thesis work I came across several unidentified species, including an alvinocaridid shrimp (Zelnio & Hourdez 2009; Chapter 1) from a family of shrimp endemic to deep sea chemosynthetic ecosystems, and anemones from active and inactive sulfide mounds (Zelnio et al. in press; Chapter 2).

The second aim was to test the null hypothesis that ELSC vent community structure is similar among geologic settings or foundation fauna types (Chapter 3). A quantitative sampling regime was employed at four study sites varying among different geologic gradients and among foundation fauna types that span a thermo-chemical gradient. Dayton (1972) defined a foundation species as a large, influential species that has a positive effect on most community inhabitants through modifying environmental parameters, species interactions and resource availability. It is hypothesized that foundation fauna can ameliorate abiotic stress by modifying the chemical and physical environment (Bruno et al. 2003). The refuge provided by the foundation species increases abundance, biomass and diversity of other associated species (Bruno & Bertness 2001).

Consequently, these actions may increase stress for other organisms. The net effect on the 4 community as a whole is that a foundation species increases standing-stock biomass due to its presence (Bruno & Bertness 2001).

Many chemoautotrophic macrofauna at hydrothermal vents can be considered foundation fauna by the definition above. They modify the physical and chemical habitat

(Johnson et al. 1994, Shank et al. 1998) and provide structural heterogeneity (Govenar &

Fisher 2007), making the local environment more amenable towards less tolerant colonizers (Shank et al. 1998). The mussels and snails of ELSC may reduce the presence of hydrogen sulfide (Henry et al. 2008, Waite et al. 2008), create habitat complexity, and expand the niche range for other associated animals. Non-chemoautotrophic fauna can also fill the last roles, but unlikely to satisfy the first role. In fact, communities hosted by barnacles and benthic cnidarians are abundant at ELSC in very low temperature diffuse venting or peripheral to venting sources. For the purposes of this study I will only be looking at communities hosted by the three dominant chemoautotrophic macrofauna and consider them as foundation species because the net effect of their presence increases standing stock biomass.

In summary, the content of this Masters thesis contributes to the field of vent ecology by quantitatively describing patterns of community structure at ELSC, testing the role of geologic variables in structuring these communities, and testing the role of microhabitat variation in structuring these communities using foundation fauna type as a proxy for the thermo-chemical environment. The geology of the ELSC and the thermo- chemical tolerances of the foundation fauna are well characterized and serve as a proxy for the indirect measurement of the abiotic environment experienced by the ELSC fauna.

Additionally, my taxonomic and systematic work will add information on species 5 diversity at these unique environments and contributes to the foundation that is taxonomic knowledge for which future ecological and biological work is dependent.

References

Anderson TR, Rice T (2006) Deserts on the sea floor: Edward Forbes and his azoic

hypothesis for a lifeless deep ocean. Endeavour 30: 131-137

Baker ET, Chen YJ, Phipps Morgan J (1996) The relationship between near-axis

hydrothermal cooling and the spreading rate of mid-ocean ridges. Earth and

Planetary Science Letters 142: 137-145

Bruno JF, Bertness MD (2001) Habitat modification and facilitation in benthic marine

communities. In: Marine Community Ecology. Sinauer Associates, Inc., Sunderland,

MA, pp 201-218

Bruno JF, Stachowicz JJ, Bertness MD (2003) Inclusion of facilitation into ecological theory.

TREE 18: 119-125

Corliss JB, Dymond J, Gordon LE, Edmond JM, von Herzen RP, Ballard RD, Green K,

Williams D, Bainbridge A, Crane K, van Andel TH (1979) Submarine thermal

springs on the Galápagos Rift. Science 203: 1073-1083

Dayton P (1972) Toward an understanding of community resilience and the potential effects

of enrichments to the benthos at McMurdo Sound. In: Proceedings of the

Colloquium on Conservation Problems in Antarctica. pp 81-96

De La Beche HT (1834) Researches in Theoretical Geology, Charles Knight, London, UK

Desbruyères D, Segonzac M, Bright M (2006) Handbook of Deep-Sea Hydrothermal Vent

Fauna (2nd ed.). Denisia, 18: pp 544 6 Ferrini VL, Tivey MK, Carbotte SM, Martinez F, Roman C (2008) Variable morphologic

expression of volcanic, tectonic, and hydrothermal processes at six hydrothermal

vent fields in the Lau back-arc basin. Geochemistry Geophysics Geosystems 9: 1-33

Fisher C (1996) Ecophysiology of primary production at deep-sea vents and seeps. In:

Uiblein F, Ott J, Stachowtish M (eds) Deep-sea and extreme shallow-water habitats:

affinities and adaptations. Biosystematics and Ecology Series, pp 313-336.

Fisher C, Childress JJ, Macko SA, Brooks JM (1994) Nutritional interactions in Galapagos

Rift hydrothermal vent communities: inferences from stable carbon and nitrogen

isotope analyses. Marine Ecology Progress Series 103: 45-55

Forbes E (1844) Report on the Mollusca and Radiata of the Aegean Sea, and on their

distribution, considered as bearing on geology. Report of the British Association for

the Advancement of Science for 1843, pp. 129–193

Gage JD, Tyler PA (1992) Deep Sea Biology. Cambridge University Press, Cambridge, UK,

520 pp.

Govenar B, Fisher CR (2007) Experimental evidence of habitat provision by aggregations of

Riftia pachyptila at hydrothermal vents on the East Pacific Rise. Marine Ecology 28:

3-14

Henry MS, Childress JJ, Figueroa D (2008) Metabolic rates and thermal tolerances of

chemoautotrophic symbioses from Lau Basin hydrothermal vents and their

implications for species distributions. Deep Sea Research Part I: Oceanographic

Research Papers 55: 679-695

Johnson KS, Childress JJ, Hessler RR, Sakamoto-Arnold CM, Beehler CL (1988) Chemical

and biological interactions in the Rose Garden hydrothermal vent field, Galapagos

spreading center. Deep Sea Research Part A. Oceanographic Research Papers 35: 7 1723-1744

Johnson KS, Childress JJ, Beehler CL, Sakamoto CM (1994) Biogeochemistry of

hydrothermal vent mussel communities: the deep-sea analogue to the intertidal zone.

Deep-Sea Research I 41: 993-1011

Kennicutt II MC, Brooks JM, Bidigare RR, Fay RR, Wade TL, McDonald TJ (1985) Vent-

type taxa in a hydrocarbon seep region on the Louisiana slope. Nature 317: 351-353

Le Bris N, Sarradin P, Caprais J (2003) Contrasted sulphide chemistries in the environment

of 13°N EPR vent fauna. Deep Sea Research Part I: Oceanographic Research Papers

50: 737-747

Luther III GW, Rozan TF, Taillefert M, Nuzzio DB, Di Meo C, Shank TM, Lutz RA, Cary

SC (2001) Chemical speciation drives hydrothermal vent ecology. Nature 410: 813-

816

Lutz RA, Shank TM, Fornari DJ, Haymon RM, Lilley MD, Von Damm KL, Desbruyères D

(1994) Rapid growth at deep-sea vents. Nature 371: 663-664

Nelson DC, Fisher CR (1995) Chemoautotrophic and methanotrophic endosymbiotic bacteria

at deep-sea vents and seeps. In: Microbiology of the Deep-Sea Hydrothermal Vent

Habitats. CRC Press, Boca Raton, pp 125-167

Page D (1856) Advanced Textbook of Geology. William Blackwood, Edinburgh, UK, 416

pp.

Podowski EL, Moore TS, Zelnio KA, Luther III GW, Fisher CR GIS-based analysis of

realized distributional patterns of diffuse flow mega-fauna on the Eastern-Lau

Spreading Center, Tonga. Submitted to Deep Sea Research Part I: Oceanographic

Research Papers.

Rau GH (1981) Hydrothermal vent clam and tube worm 13C/12C: further evidence of 8 nonphotosynthetic food sources. Science 213: 338-340

Rau GH, Hedges JI (1979) Carbon-13 depletion in a hydrothermal vent mussel: suggestion of

a chemosynthetic food source. Science 203: 648-649

Rhoads DC, Lutz RA, Revelas EC, Cerrato RM (1981) Growth of bivalves at deep-sea

hydrothermal vents along the Galápagos Rift. Science 214: 911-913

Sarrazin J, Juniper SK, Massoth GJ, Legendre P (1999) Physical and chemical factors

influencing species distributions on hydrothermal sulfide edifices of the Juan de Fuca

Ridge, northeast Pacific. Marine Ecology Progress Series 190: 89-112

Sdrolias M, Müller RD (2006) Controls on back-arc basin formation. Geochemistry

Geophysics Geosystems 7: Q04016 (doi:10.1029/2005GC001090)

Shank TM, Fornari DJ, Von Damm KL, Lilley MD, Haymon RM, Lutz RA (1998) Temporal

and spatial patterns of biological community development at nascent deep-sea

hydrothermal vents (9deg.50'N, East Pacific Rise). Deep-Sea Research II 45: 465-

515

Snelgrove PV, Smith CR (2002) A riot of species in an environmental calm: the paradox of

the species-rich deep-sea floor. Oceanography and Marine Biology: An Annual

Review 40: 311-342

Tunnicliffe V, Fowler MR (1996) Influence of sea-floor spreading on the global

hydrothermal vent fauna. Nature 379: 531-533

Tunnicliffe V, Embley RW, Holden JF, Butterfield DA, Massoth GJ, Juniper SK (1997)

Biological colonization of new hydrothermal vents following an eruption on Juan de

Fuca Ridge. Deep Sea Research Part I: Oceanographic Research Papers 44: 1627-

1644

Van Dover CL (1995) Ecology of Mid-Atlantic Ridge hydrothermal vents. In: Hydrothermal 9 Vents and Processes. Geological Society Special Publication, No. 87: 257-294

Van Dover C, German C, Speer K, Parson L, Vrijenhoek R (2002) Evolution and

biogeography of deep-sea vent and seep invertebrates. Science 295: 1253-1257

Von Damm K (1990) Seafloor hydrothermal activity: black smoker chemistry and chimneys.

Annual Review of Earth and Planetary Science 18:173-204.

Waite TJ, Moore TS, Childress JJ, Hsu-Kim H, Mullaugh KM, Nuzzio DB, Paschal AN,

Tsang J, Fisher CR, Luther GW (2008) Variation in Sulfur Speciation with Shellfish

Presence at a Lau Basin Diffuse Flow Vent Site. Journal of Shellfish Research 27:

163-168

Zelnio KA, Hourdez S (2009) A new species of Alvinocaris (Crustacea: Decapoda:

Alvinocarididae) from hydrothermal vents at the East-Lau Spreading Center,

Western Pacific. Proceedings of the Biological Society of Washington 122: 52-71

Zelnio KA, Rodriguez E, Daly M (in press) Hexacorals (Anthozoa: Actiniaria, Zoanthidea)

from hydrothermal vents in the South-western Pacific. Marine Biology Research.

10 CHAPTER 1

A new species of Alvinocaris (Crustacea: Decapoda: Caridea: Alvinocarididae) from hydrothermal vents at the Lau Basin, southwest Pacific, and a key to the species of Alvinocarididae

Abstract

We describe Alvinocaris komaii sp. n. from hydrothermal fields at the Eastern Lau

Spreading Center (ELSC). Adults of this species are distinguished in the field from other alvinocaridids at the ELSC by their larger size and orange-white carapace. Additionally, they appear to preferentially inhabit mussel beds composed of Bathymodiolus brevior. A. komaii differs from all known species in the genus by a distinctive, deep notch mesially on the telson and accessory spinules on the dactyli of the third to fifth pereopods arranged in 2 rows. A suite of morphological characters separates A. komaii from other alvinocaridids. We analyze the degree of morphological variation in A. komaii and discuss affinities of the Pacific species of Alvinocaris. Molecular data from the mitochondrial COI gene is used to compliment this description and a key to the species of the family

Alvinocarididae is included with locality information.

Introduction

Caridean shrimp of the family Alvinocarididae (Christoffersen 1986; Komai and

Segonzac 2003) are well-documented from hydrothermal vents and cold seeps worldwide

(Komai and Segonzac 2005; Martin and Haney 2005). This family is composed of 7 genera: Alvinocaris Williams and Chace, 1982, Rimicaris Williams and Rona, 1986, 11 Chorocaris Martin and Hessler, 1990, Opaepele Williams and Dobbs, 1995, Mirocaris

Vereshchaka, 1997, Nautilocaris Komai and Segonzac, 2004 and Shinkaicaris Komai and Segonzac, 2005. Alvinocaris is the most species-rich genus in the Alvinocarididae, with 11 described species represented by 7 vent-endemic species and 4 seep-endemic species from nearly all known sites in the Atlantic and Pacific Oceans. Species in the genus Alvinocaris have not been reported from non-chemosynthetic environments.

Escobar-Briones & Villalobos-Hiriart (2003) noted an “Alvinocaris sp.” off the Banco

Chinchorro in 176-203 m water depth, but provided no taxonomic or descriptive details.

At the Eastern Lau Spreading Center (ELSC, Fig. 1), a Ridge2000 designated

Integrated Studies Site, 2 alvinocaridid shrimp, Chorocaris vandoverae Martin and

Hessler, 1990 and Nautilocaris saintlaurentae Komai and Segonzac, 2004, and 1 hippolytid shrimp, Lebbeus sp., have been identified from collections and video during recent expeditions to the ELSC. We describe a new species of Alvinocaris from hydrothermal vents at the ELSC. This species represents the fourth genus of caridean shrimp reported from the ELSC and eleventh species in the genus Alvinocaris.

Materials and Methods

Specimens were collected during the June 2005 TUIM07MV and September 2006

MGLN07MV cruises to the ELSC. Collection was done using the JASON II remotely operated vehicle and brought onboard the R/V Melville for study. Tools used to collect individuals were the manipulator arm, suction sampler and the mussel pot, a quantitative collection device to collect intact samples of mussel and snail bed communities.

Specimens studied came from the following sites (Fig. 1): Kilo Moana (20°9′S, 12 176°12′E, 2620 m depth) dives J2-154 (1 female), J2-164 (9 females, 1 male, 1 indeterminate), J2-230 (1 female) and J2-235 (19 females, 6 males, 2 indeterminate),

TowCam (20°19′S, 176°8′E, 2700 m depth) during dive J2-240 (3 indeterminate), and

ABE (20°45′S, 176°11′E, 2145 m depth) during dive J2-237 (7 females, 2 males).

Indeterminate individuals were missing their pleopodal half, therefore they could not be sexed by examining for the appendix masculina. We confirmed by video that A. komaii is also present at Tu’i Malila (21°59’S, 176°34’E, 1880 m depth, Fig. 1). No juveniles were obtained in our collections. Females collected in either June 2005 or September 2006 were not carrying eggs.

Figure 1: Map of collection

sites at the Lau Basin with

topographic features.

Background image is

courtesy of the Ridge

Multibeam Synthesis Data

Portal of the Marine

Geoscience Data System.

Type specimens are deposited at the National Museum of Natural History in 13 Washington D.C., USA [holotype USNM (1116499), paratypes USNM (1116500–

04)]. Additional voucher material is held in the laboratory of Dr. Charles R. Fisher in the

Department of Biology at Pennsylvania State University (University Park, PA USA).

The descriptive terminology used follows that of Komai & Segonzac (2005).

Carapace length was measured from the posterior margin of the orbit level to the

posterior margin of the carapace. Rostral length was measured from the anterior-most

part of the rostrum to the posterior margin of the orbit. Carapace width was measured

from the widest sections of the branchial regions. The total length was measured from the

anterior-most part of the rostrum to the posterior margin of the telson. Stata (Intercooled

Stata version 9.2, College Station, TX USA) was used to analyze morphometric data.

One-way ANOVA was used to test differences in characters between sites and gender,

using Bonferroni correction for multiple comparisons when appropriate. Linear

regression was used to test the significance of the relationship between continuous

characters.

Frozen tissues (ca. 0.2 g) were digested overnight with proteinase K at 55˚C in 0.5 ml PK-SDS lysis buffer (Tris-HCl 50 mM pH 8.0, NaCl 100 mM, 10 mM EDTA, 1%

SDS). Genomic DNA was then purified using standard phenol/chloroform extractions and stored at 4˚C in TE (Tris 10 mM, 1 mM EDTA pH 8.0). The mitochondrial gene coding for cytochrome oxidase subunit I (COI) was amplified with the primers used by Folmer et al. (1994) and following the conditions reported in Black et al. (1997).

Sequences of each strand were generated by using chain-terminating fluorescently

labeled nucleotides with universal primer T3 or T7 and the Big Dye Terminator V3.1 14 Cycle Sequencing kit (Applied Biosystems). Reactions were subsequently run on a 16- capillary 3130 Applied Biosystems sequencer. The 2 COI sequence strands for each species were assembled and proofread in CodonCode Aligner to generate a continuous fragment. Sequences were aligned manually.

In addition to the species already available in the GenBank database (see Fig. 7 for accession numbers), sequences for 2 species were used for this study: Alvinocaris komaii sp. nov. (two individuals from ABE were used and yielded an identical sequence) and Alvinocaris muricola Williams, 1988 from the Florida Escarpment in the Gulf of

Mexico (one individual, 3200m depth, for more details on collection site, see Cordes et al. (2007)), and from the REGAB area of the Gulf of Guinea (one individual, 3160 m depth, for more details on the site, see Ondréas et al. (2005)). The sequence from Lebbeus carinatus (de Saint Laurent 1984) (Hippolytidae) was used as an outgroup. The tree was constructed using the Neighbor Joining method on Kimura-2-Parameter distances on a

600-bp alignment. Bootstrap values were calculated on 1000 re-sampling replicates.

Taxonomic Results

Alvinocaris komaii, new species

Figs. 2-6

Material examined.---Holotype: female, Kilo Moana, TL= 61.4 mm, CL=15.4 mm, CW=8.8 mm, RL=5.6 mm. Paratypes: males (n=9) – TL=60.0-72.7 mm, CL=13.3-

16.9 mm, CW=7.9-11.2 mm, RL=7.1-9.5 mm; females (n=36) – TL=43.9-92.2 mm,

CL=9.8-23.2 mm, CW=5.7-14.2 mm, RL=5.1-14.9 mm; indeterminate (n=7) – 15 TL=posterior ends broken, CL=14.0-18.3 mm, CW=7.8-11.3 mm, RL=6.1-9.4 mm.

Carapace (Fig. 2a,b).---Integument thin, reflective, minutely punctuate. Rostrum almost distally curved, perceptibly elevated above the horizontal in the distal half, sharply pointed tip, reaching one-third to three-quarters length of the second peduncular article of antennule; one-quarter to one-third the carapace length; dorsal margin raised into thin serrate crest containing 9-12 teeth (4-6 teeth on carapace proper) of decreasing strength towards the distal end, about two-thirds length of the crest is continued onto carapace, posterior-most tooth arising from two-thirds carapace length, base of rostrum deflecting from dorsal line of carapace at approximately 15°. Ventral margin less prominent and armed with 2-6 subterminal teeth. Sample rostral tooth formulas (dorsal/ventral) from the

2005 specimens are 12/6, 10/2, 10/4, 10/4, 10/2, 10/3, 9/4, 10/4, 11/4 and 9/6. Lateral carina broadened proximally and confluent with orbital margin. Carapace with acuminate antennal spine distinct, pterygostomian spine acuminate and prominent. Prominent antennal carina curving posteroventrally to intersect obliquely with carina extending from pterygostomial spine at about mid-length of carapace, associated groove continuing indistinctly posterior.

Abdomen (Fig. 2a).---Abdomen of both male and female broadly arched dorsally, narrowest part of sixth somite about one-half the width of first somite; fourth somite drawn posterolaterally to acuminate spine, flanked dorsally by 0-4 much more slender and smaller spines; posterolateral corner of fifth pleuron acuminate and dorsally with 2-4 spines analogous to those on fourth somite; sixth somite with mid-dorsal length about

1.5-1.8 that of fifth and 1.2-1.8 as long as wide, smaller posterolateral spine acute; only fifth somite with strong, posteriorly directed spine on sternite. 16

Figure 2: Alvinocaris komaii, new species, holotype female (a-d) and paratype female (e). a) whole specimen, right lateral view; b) rostrum, left lateral view; c) antennular peduncles, dorsal view; d) telson and uropods, dorsal view; e) close-up of posterior margin of paratype telson showing occasional plumose setae. Scale bar = 5 mm (a) or 2 mm (b-e).

Telson (Fig. 2d, e).---Telson elongate, subrectangular; length about 2.4-2.9 anterior width, 2.9-3.3 posterior width, and about 1.4-1.8 length of sixth somite, not 17 including posterior spines; armed with 7 pairs of dorsolateral spines of nearly uniform size, the anterior-most pair slightly smaller than the 6 posterior-most pairs, posterior margin concave with a distinct notch, notch depth is 0.1-0.2 posterior width of telson, posterior margin of telson with 6-10 pairs of spines on each side of notch, can be unequally paired. Sample telson spine formulas from the 2005 specimens are 7/8, 6/6,

8/10, 6/6, 7/7, 6/6 and 7/6 on the left and right sides of the notch, repectively. Telson overreaching posterior margin of uropods.

Eyes (Fig. 2b, c).---Eyes with cornea imperfectly developed and unfaceted though diffusively pigmented in adults (no juveniles analyzed), but with internal facet-like pattern evident; cornea ovate in outline though fused to each other mesially, and each with a small upturned spine on the anterodorsal surface.

Antennae (Fig. 2c).---Antennular peduncle reaching distal margin of antennal scale; first article 1.1-1.5 length of second and about 1.9-2.3 length of third, all measured on ventral margin; stylocerite well separated from peduncle, tapering to slender elongate tip variably reaching as far as three-quarters to full length of second article; basal article with dorsolateral margin extended into strong lateral spine reaching half the length of the second article and closely appressed to second article, small distal spine ventrally, no obvious distomesial spine; shorter second article with stronger mesiodistal spine.

Dorsolateral and ventromesial flagella approximately equal in length, about the length of carapace, thickened in basal half. Antennal scale length 1.6-2.3 the width, distolateral tooth strong, falling short of broadly rounded distal margin of blade.

Mandible (Fig. 3a, b).---Mandibles similar, with 2-segmented palp, distal segment with long setae on lateral margin and posterior face as illustrated, proximal segment with 18 4 long, plumose setae on distolateral margin. Incisor process with an upper portion bearing 1 blunt tooth, lower portion projecting further than upper with 8 sharp teeth, process distinct from incisor process, separated from it by a deep notch, rounded tip lacking minute setae.

First maxilla (Fig. 3c, d).---Proximal endite oval, curving anteriorly (dished anteriorly) bearing numerous distal marginal setae, densest around narrow anteromesial tip, armed with teeth on distolateral margin; distal endite with broad base, distal margin curving anteriorly, not armed with teeth, numerous setae on proximal margin and posterior surface, longer plumose setae placed regularly around distal tip and lateral margin of endite; palp with round tip and mesial, subterminal notch without setae.

Second maxilla (Fig. 3e, f).---Endites dished anteriorly, densely setose distally on margins and submarginally, proximal endite of 2 lobes, distal lobe with small, setose protrusion on anterior margin, distal endite spatulate in posterior view, with uniform row of small setae along lateral margin; palp straight with short row of small, plumose setae on lateral margin, tip unarmed; scaphognathite almost rounded anteriorly, fringed with long plumose setae anteriorly, shorter plumose setae on mesial and lateral margins, narrowing to acuminate posterior lobe armed around tip and mesial margin with series of very long, strong setae, a row of small setae proximally on mesial margin.

19

Figure 3: Alvinocaris komaii, new species, holotype female (a-l). a) mandible, interior view; b) mandible, exterior view; c) first maxilla, exterior view; d) first maxilla close-up of teeth on distolateral margin of proximal endite; e) second maxilla, interior view; f) second maxilla, interior view; g) close-up view of second maxilla endites and palp, exterior view; g) first maxilliped, exterior view; h) first maxilliped, interior view; i) second maxilliped, interior view; j) second maxilliped with palp, setae removed, exterior view; k) third maxilliped, ventral view; l) third maxilliped, dorsolateral view. Scale bars

= 0.5 mm. 20 First maxilliped (Fig. 3g, h).---Endite strongly dished anteriorly, fringed along lateral margin by dense setae, along anterior margin by numerous plumose setae; exopod ovate, fringed distally by long plumose setae, submarginal ridge laterally with palp reduced and rounded with setae; epipod bilobed, unarmed.

Second maxilliped (Fig. 3i, j).---Pediform but rather flattened; coxa fringed mesially by long, dense, plumose setae, fused basis-ischium with regular mesial row of long, strong, sparsely plumose setae, opposite margin and merus, carpus, propodus bordered by long, plumose setae, dactylus bordered by long plumose or serrate setae, forming particularly dense, nest-like pad around mesial part of dactyl; epipod leaf-like, unarmed; podobranch rudimentary with pointed tip, mesial branch without terminal seta, no tooth-like projections observed on lateral margin.

Third maxilliped (Fig. 3k, l).---Long, 4-segmented, reaching as far as the distal end of antennal scale; terminal segment triangular in cross-section, tapered distally, tip with 2 spines and additional setae, an irregular row of about 4 additional spines subterminally on mesial face, 5 groups of distally directed serrate setae arranged in close- set, transverse tracts along mesial face, groups overlapping to form a longitudinal pad; posterolateral face of terminal segment somewhat dished, angle between posterolateral and anterolateral faces armed with row of 7 or 8 slender spines or spine-like setae; carpus with pads of dense setae on distal two-thirds, similar and adjacent to those of terminal segment; merus-ischium with row of long, plumose setae, otherwise armed as illustrated; coxa with small epipod, with tuft of long, plumose setae at junction.

First pereopod (P1, Figs. 4a, 5c, d).---Reach to half the length of terminal segment on third maxilliped, robust; fingers curved downwards and outwards, together 21 concave laterally, fixed finger twice the width of dactyl basally, opposing edges of fingers each armed with row of minute uniform teeth close-set against one another, teeth on dactyl somewhat longer than on fixed finger, row on dactyl angled towards convex side to interdigitate with teeth on fixed finger, finger tips slightly spooned by teeth fanned around edge, latter teeth fused to form corneous edge around lateral border of dactyl tip, line of sensory setae on moving finger’s concave surface running parallel to teeth, setae on fixed finger not obvious; dactyl fractionally outreaching fixed finger, palm half the length of finger in female and same length in males; carpus short, cone-shaped, cupped distally to accommodate palm, with smaller blunt protuberance on distomesial margin, lateral ridge produced distally into strong process with pinched tip (process slender, acuminate in female paratype); dense, clearly delineated pad of strong, serrate setae posteriorly between pinched and smaller process; merus, ischium somewhat flattened, they and distinct basis and coxa armed as illustrated.

Second pereopod (P2, Fig. 4b).---Shorter and more slender than first, reaching half the length of antennal scale; fingers subequal to palm, similar in size and shape, opposing edges without gap, each pectinate with single row of short teeth directed obliquely distally, row beginning about 0.2 from base of dactyl, fixed finger has teeth all its length increasing slightly in size distally, terminating in larger spine at each finger tip, terminal spines cross when chela is closed, with 2 tufts of long setae on dactyl; carpus, merus armed as illustrated, ischium with single spine at about three-quarters length (1 individual showed 2 spines on 1 side).

22

Figure 4: Alvinocaris komaii, new species, holotype female (a-g) and paratype male (h). a) left first pereopod, external view; b) left second pereopod, external view; c) left third pereopod, external view; d) left third pereopod dactylus and carpus, lateral view; e) right fourth pereopod, inner view; f) left fifth pereopod, external view; g) right first pleopod, inner view; h) appendix masculina. Scale bars = 1 mm. 23 Third to fifth pereopods (P3-P5, Figs. 4c-f, 5a, b).---Similar in length although merus becomes progressively shorter from the P3 to P5 and propodus longer, P3 outreaching antennal scale by 0.5 propodus; dactyls short, armed with single corneous spine and single accessory spinule in holotype, 2 rows of 4 or 5 accessory spinules in paratypes on flexor surface, smallest proximally, longest distally; propodus with irregular, composite row of spines ventrolaterally becoming denser distally, row shortest and sparsest on P3, longest and densest on P5; carpus of each pereopod with distodorsal extension over proximal extensor surface of propodus; ischium and merus of P3 stronger than in P4 and P5, meri of pereopods with 3 spines on P3 and P4, without spines on P5, ischium of pereopods armed with 2 posteroventral spines on P3 and P4, none or 1 on P5.

Figure 5: Alvinocaris komaii, new species, holotype female (a, c) and paratype male (b, d). Variation in third pereopod, ventral view (a, b) and chelae of first pereopod (c, d).

Scale bars = 1 mm.

24 Pleopods (Fig. 4g, h).---Well-developed, endopods about half the length of exopod on first pleopod, subequal with exopod in pleopods 2-5; appendix interna of pleopods 2-4 well-developed and smooth, of pleopod 5 twice as wide, parallel-sided, with

30-50 cincinnuli distributed in fingernail-shaped pad at tip on mesial surface; appendix masculina with approximately 8 slender spines around tip and subterminally.

Uropods (Fig. 2d).---With exopod and endopod subequal, slightly shorter than telson, exopod with movable spine mesial to distolateral tooth half its length; diaresis sinuous.

Etymology.---Named in honor of Dr. Tomoyuki Komai of the Natural History

Museum and Institute in Chiba, Japan, for his significant contributions to the taxonomy of the Alvinocarididae.

Variation.---There are no significant differences between males and females with regards to any of the examined characters (dorsal and ventral rostral teeth numbers, abdominal pleuron (3-5) spine numbers, telson dorsolateral spine and posterior marginal spine number) or measurements (carapace length, carapace width, total body length, rostral length, telson length and anterior/posterior widths, antennal scale length and width, pereopod 1 palm width and height, pereopod 3 carpus, merus and propodus lengths and antennal peduncle segment (1-3) lengths and widths) (P>0.08). It should be noted that very few males were collected (9 out of 45 individuals with intact second pleopods). An increased number of individuals may reveal patterns in the ratio of pereopod 1 palm width to height and the ratio of propodus length to carpus length.

Though Webber (2004) found dimorphic variation between the sexes in Alvinocaris niwa,

Kikuchi & Ohta (1995) observed that variation in the first pereopod chelae of A. 25 longirostris corresponded to increase in carapace length and between the left and right chelae of a single individual. Additionally, variation in the overall appearance of the first pereopod chelae has been noted for the genus in general (Komai & Segonzac, 2005), A. methanophila (Komai et al., 2005) and in other alvinocaridids: Chorocaris paulexa

(Martin & Shank, 2005) and Opaepele susannae (Komai et al., In Press). On the other hand, distinct variation in the first pereopod chelae was not observed in Shinkaicaris leurokolos (Komai & Segonzac, 2005).

Individuals of Alvinocaris komaii collected from ABE appear to be more robust than those collected from KM. Because there were 3 individuals from TC that consisted only of the anterior portion of the animal (no pleopods or telson), only ABE and KM collections are compared. There was no difference in rostral armature, but rostral length was significantly longer for specimens from ABE (P≤0.001). A. komaii from ABE also have larger ratios of rostral length to carapace length (P<0.001), though carapace length was not significantly different between sites (P=0.12). Hence, rostra of ABE individuals are larger irrespective of body size, yet this trend appears to be driven by 4 out of 7 individuals collected at ABE. The first segment of the antennular peduncle is longer in

ABE individuals (P=0.001) as is the ratio of the first segment to the third segment of the antennular peduncle (P=0.002). Palm width, height, and the ratio of width to height are also larger among individuals from ABE than from KM (P<0.02). In conclusion, individuals from our collections at ABE may appear proportionally larger than those from the KM collections, but disproportionately have longer rostra and antennular peduncles than KM individuals (see Table 1). It should be noted that sample sizes of individuals collected at ABE are low and it may be premature to extend this observation to the 26 population level at this particular site.

Table 1: Ratios of rostrum length to carapace length (RL/CL), antennular peduncular segment 1 length to segment 3 length (AP1/AP3), and pereopod 1 palm width to height

(Palm W/H) for Alvinocaris komaii sp nov from three sites at the Eastern-Lau Spreading

Centre.

Ecology.---Alvinocaris komaii was observed at 4 of the 6 study sites targeted by the Ridge2000 ELSC Integrated Study Site. We first discovered this species in the 2005 expedition in quantitative whole-community collections from KM, where it occurs in great abundance. During the 2006 expedition, A. komaii was discovered at TC, ABE and

TM in addition to KM (Fig. 1). The depth spans from 1880 m in the southern-most site,

TM, to 2720 m in the northern-most sites, KM and TC. At each of these sites, it co- occurs with the alvinocaridids Nautilocaris saintlaurentae and Chorocaris vandoverae.

The hippolytid, Lebbeus sp. nov. (Michel Segonzac, personal communication), also occurs at ELSC. Despite being documented on and near the mussel Bathymodiolus 27 brevior (von Cosel et al. 1994), Lebbeus sp. nov. typically inhabits the communities along the vent’s periphery, whereas the 3 alvinocaridids inhabit the communities directly influenced by hydrothermal discharge.

Most commonly, A. komaii is seen on top of beds composed of the chemoautotrophic mussel, B. brevior (Fig. 6a, b). This habitat is common among alvinocaridid shrimp, though some species are seen exclusively on hydrothermal chimneys (i.e. Rimicaris) or utilize both the geologic and biologic substrate. Video records show A. komaii making relatively few excursions into beds of the chemoautotrophic snail, Ifremeria nautilei Bouchet and Warén, 1991, as well on the bare rock of hydrothermal chimneys (Fig. 6c). On rare occasion, A. komaii has been observed in beds of the provannid snail Alviniconcha hessleri Okutani and Ohta, 1988. Other fauna found in association with A. komaii include the decapod crabs Austinograea alayseae

Guinot, 1989, Austinograea williamsi Hessler and Martin, 1989 and Paralomis hirtella de

Saint Laurent and MacPherson, 1997; the barnacle Eochionelasmus ohtai Yamaguchi and

Newman, 1990; the gastropods Desbruyeresia cancellata Warén and Bouchet, 1993,

Lepetodrilus schrolli Beck, 1993 and Olgasolaris tollmanni Beck, 1992; and the polychaetous annelids Archinome sp. and Opisthotrochopodus trifurcus Miura and

Desbruyères, 1995.

Alvinocaridids are typically described as either primary consumers or necrophagous (Segonzac et al. 1993). Video imagery documented A. komaii feeding on the verrucamorph barnacle, E. ohtai, which was crushed incidentally by the submersible.

Eochionelasmus ohtai co-occurs with A. komaii as it frequently colonizes the shells of B. brevior. Additionally, A. komaii was observed on rock covered in bacteria and barnacles. 28 We have not observed A. komaii directly feeding on the mussels. It is likely that this shrimp species is a generalist, feeding from several potential pools including grazing bacteria from bare rock and mussel shells and feeding opportunistically on other sessile fauna or necrotic material. The diet of the new species is uninvestigated.

Little can be ascertained about the reproductive biology of A. komaii from these individuals. Though our collections were haphazard (specimens come from intact community collections for ecological analyses, targeted for suction sampler or as bycatch in other collections of snails and mussels) and not quantitative, there appears to be a sex- ratio skew in favor of females. This skew has been noted for Alvinocaris muricola off the

West African Margin, Gulf of Guinea (Ramirez-Llodra and Segonzac 2006). We have not observed gravid females, or females carrying egg masses between their pleopods, in any video we have viewed from June 2005 or September 2006. Fertilization and copulation of

A. komaii follows typical courtship observed among caridean shrimp (Tyler and Young

1999). One instance of courtship was observed during the September 2006 cruise (video available upon request from corresponding author). Courtship was commenced when one individual nudged into another on the substrate (shell of B. brevior). The nudged individual grasped the other’s carapace with pereopods 2 and 3. Both individuals then faced each other ventrally and moved into the water column where copulation took place immediately. Both individuals then swam together back to the substrate (shell of B. brevior) about 10 cm from the starting point. Since a copulation event was observed in

September, it is plausible that the development period for embryos is during November to

December. More collections at other times of the year would be needed to discern the reproductively active period of A. komaii. Individuals of Chorocaris vandoverae that 29 were collected and observed from the same locations as A. komaii have been observed to be gravid both in June 2005 and September 2006.

Figure 6: In-situ photographs of

Alvinocaris komaii from the

ABE site. a) Several A. komaii

on top of the mussel

Bathymodiolus brevior on a

chimney wall. b) Closer view

on B. brevior (note the presence

of the limpet Lepetodrilus

schrolli and barnacle

Eochionelasmus ohtai on

shells). Other alvinocaridids,

either Nautilocaris

saintlaurentae or Chorocaris

vandoverae are present on the

right side of the photo on the

bare substrate. c) On bare

substrate, note the gastropod

Ifremeria nautilei below and the

barnacles E. ohtai to the left on

the bare substrate.

30 Molecular Phylogeny.--- The molecular phylogeny of the Alvinocarididae based on the COI sequence shows that A. komaii is genetically distinct from all other species available in the databases and from A. muricola (Gulf of Mexico and REGAB, Fig. 7).

The Mirocaris group forms a very well supported monophyletic group, apart from the

Alvinocaris/Opaepele/Rimicaris/Chorocaris clade. In this latter group, the sequence referred to as "Alvinocarididae Blake Ridge" probably corresponds to Alvinocaris methanophila Komai, Shank & Van Dover, 2005 (see Van Dover et al. 2003), the second species collected from that locality with A. muricola. It appears clear that Alvinocaris is polyphyletic and that A. komaii belongs to the Alvinocaris/Opaepele/Rimicaris/

Chorocaris clade. In that clade, the position of A. komaii is uncertain, as the bootstrap value is only 39.7%.

Figure 7 (next page): Phylogenetic tree of the Alvinocarididae based on a 600-bp alignment of the partial COI sequence. Lebbeus carinatus was used as an outgroup. All

GenBank accession numbers appear after the species names. Bootstrap values are given for the branches. The arrow points at the position of the new species. 31

32 Discussion

Morphological affinities.---Alvinocaris komaii is characterized from all known

Alvinocaris by two apomorphic characters: a distinctive notch in the telson and 2 rows of accessory spinules of the dactyli of pereopods 3-5. A. lusca Williams & Chace, 1982 and

A. dissimilis Komai & Segonzac, 2005, are reported to be very shallowly notched. . The notch in A. dissimilis is a more rare occurrence (Komai & Segonzac, 2005). In comparison to A. komaii, the notch in A. lusca is shallow and can vary from more of a sinusoidal edge to a distinct shallow notch in some individuals. The posterior margin of the third abdominal pleuron of A. lusca is reported to be unarmed (Komai and Segonzac

2005; Williams and Chace 1982), but 35 out of 43 individuals of A. komaii with intact abdominal pleura had at least 1 distinct marginal spine on at least 1 side of the third pleuron (Table 2). In A. komaii, this is a highly variable character. Marginal spines on the fourth and fifth abdominal pleurae are shown to be highly variable within and between species (Table 2, Komai & Segonzac, 2005). Alvinocaris komaii is further separated from

A. lusca by the following suite of characters: strong pterygostomian tooth, shorter antennal scale, lower telson length to width ratios posteriorally and anteriorally, and a somewhat shorter reach of the rostrum (Table 2).

Alvinocaris brevitelsonis Kikuchi & Hashimoto, 2000 is described from the

Okinawa Trough. A. brevistelsonis is only known from the holotype, (see Komai &

Segonzac 2005 for discussion) and differs from A. komaii in having a weak pterygostomian tooth, a convex posterior margin of the telson that is shorter than uropod margin, larger ratio of telson length to posterior width, and a larger ratio of length to height of pereopod 1 palm (Table 2). Alvinocaris brevistelsonis is further distinguished 33 from A. komaii by having 2 pairs of posteromarginal plumose setae. Plumose setae are sometimes present on the posterior telson margin in A. komaii, but appear to represent an abnormality and can be variable in number (Fig. 2d, e).All other species of Alvinocaris are markedly different from A. komaii (see Table 2 for comparison of Pacific Ocean species and Komai & Segonzac, 2005 for a detailed analysis of the genus).

Several undescribed specimens of Alvinocaris are mentioned in previous papers.

Desbruyères et al. (1994) described the initial ecology of the North Fiji and Lau back-arc basins. In their paper, they refer to “Alvinocaris sp.” (also referred to as Alvinocaris sp. D in Martin & Haney 2005) living on mussel beds at 2 sites at the Lau Basin, Hine Hina and Vai Lili, which were not visited during the expeditions our specimens were collected from. It is likely that the species referred to as “Alvinocaris sp.” in Desbruyères et al.

(1994) is A. komaii, but it should be noted that another alvinocaridid shrimp was later described by Komai and Segonzac (2004) from the North Fiji and Lau back-arc basins in the description of a newly-erected genus, as Nautilocaris saintlaurentae. However, adults of A. komaii and N. saintlaurentae are markedly different and easy to distinguish from photograph or video imagery. Komai & Segonzac (2004) mentioned an undescribed species of Alvinocaris from the ELSC and noted it was distinguishable from N. saintlaurentae and Chorocaris vandoverae by its “well-developed rostrum and the red color of the cephalothorax”. Komai & Segonzac (2005) also noted the affinity of this

Alvinocaris species from the Lau Basin to an undescribed species in the Bismarck Sea. It is unclear whether A. komaii represents this species, but our extensive survey of the vent communities at 4 sites along the ELSC resulted in no other undescribed alvinocaridid. To date we have found no other description of an Alvinocaris resembling A. komaii as 34 described in this study.

Phylogenetic affinities.---The phylogenetic tree, based upon 600 bp of the mitochondrial COI nucleotide concurs with earlier molecular phylogenetic work of the family (Shank et al. 1999). There are distinct Opaepele/Chorocaris/Rimicaris (O/C/R),

Alvinocaris and Mirocaris clades with well-supported bootstrap values. With the addition of A. komaii, deeper branching patterns between the Alvinocaris and the O/C/R clades remain unclear. Although A. komaii seems to cluster with the O/C/R clade and not the monophyletic Alvinocaris clade, this is supported by low bootstrap values (39.7%).

Increased sampling of genes and taxa are needed to distinguish inter-generic relationships within the Alvinocarididae.

Our phylogeny agrees with the earlier phylogenetic work of Shank et al. (1999) and the revision of the genus Alvinocaris by Komai & Segonzac (2005) in that geography appears to play little role in shaping Alvinocarididae phylogeny. Clustering appears to be consistent with morphology. The Mirocaris clade is molecularly distinct from the O/C/R and Alvinocaris clades and species share the presence of “strap-like” epipods on the third maxilliped and pereopods 1-4. Nautilocaris saintlaurentae is also described as having epipods on the third maxilliped and pereopods 1-4 (Komai and Segonzac 2004), a character potentially grouping it with the Mirocaris clade. Nautilocaris saintlaurentae also has a laterally-compressed, dentate rostrum, a plesiomorphic character in common with the Alvinocaris clade. We hypothesize that N. saintlaurentae should occupy a position basal to the Mirocaris clade if the presence of the epipods is synapomorphy of that clade. The Alvinocaris clade is composed of individuals with typical Alvinocaris morphology: a laterally compressed, dentate rostrum, lack of epipods on the third 35 maxilliped and pereopods 1-4, dorsolateral spines on telson arranged linearly, acuminate antennal tooth, 1 or 2 rows of accessory spinules on dactyli of pereopods 3-5. Members of the O/C/R clade share the absence of epipods on the third maxilliped and pereopods 1-

4, acuminate antennal spine, and 1 or 2 rows of spines on dactyli of pereopods 3-5 with the Alvinocaris clade, but differ in having a nonlinear arrangement of dorsolateral spines on the telson and a dorsoventrally compressed, triangular rostrum lacking dentation.

Opaepele loihi has minute, inconspicuous dentation while O. susannae lacks any remnant of dentation and more closely resembles the Chorocaris/Rimicaris clade (Komai et al. In

Press). Alvinocaris komaii has all the characteristics of belonging to the Alvinocaris clade and lacks the rostral and telson characters defining the O/C/R clade. It is unclear why A. komaii groups with the O/C/R clade, but the low bootstrap value shows this grouping lacks statistical support. The presence of 2 rows or accessory spinules may suggest a closer affinity to a clade composed A. niwa/Shinkaicaris plus the O/C/R clade.

36 Table 2: Characters of Alvinocaris spp. from the Pacific Ocean. l=length, w=width, h=height. 37 Key to Family Alvinocarididae

1. Rostrum ridged, compressed dorsolaterally, armed with teeth dorsally, sometimes ventrally...... 2

– Rostrum broadly rounded dorsally or faintly ridged, unarmed or with rudimentary denticles on the dorsal surface, triangular, flattened dorsoventrally...... 14

2. Antennal tooth distinctly buttressed, telson dorsolateral spines arranged in a sinusoidal row, more than 2 rows of spines on dactyli of pereopods 3-5. . . . Shinkaicaris leurokolos

(Kikuchi and Hashimoto 2000) [Minami-Ensei Knoll, Okinawa Trough, 705 m]

– Antennal tooth not buttressed, telson dorsolateral spines not distinctly arranged in a sinusoidal row, 1 or 2 rows of accessory spinules on dactyli of pereopods 3-5. . . . 3

3. Third maxilliped to fourth pereopod with strap-like, terminally hooked epipods, telson with 7-9 dorsolateral spines arranged in slightly sinusoidal row and with 12-19 spines on posterior margin...... Nautilocaris saintlaurentae

Komai and Segonzac 2004 [North Fiji and Lau Back-Arc Basins, 1700-2700 m]

– No strap-like epipods present on third maxilliped to fourth pereopod, dorsolateral spines on telson arranged in a straight row...... Alvinocaris 4

4. Posterior margin of telson with more than 2 pairs of spines ...... 5

– Posterior margin of telson with 2 pairs of spines at lateral corners and 10–16 plumose setae ...... 8

5. Posterior margin of telson with mesial spines of subequal length, lacking plumose setae mesially; ventral margin of rostrum with 1 tiny tooth ...... A. stactophila

Williams, 1988 [Upper Louisiana Slope, Gulf of Mexico, 534 m]

– Ventral margin of rostrum with 2 or more teeth; posterior margin of telson with mesial 38 spines of greatly unequal length and 1 to 3 mesial pairs of short plumose setae . . . 6

6. Rostrum with more than 5 ventral teeth; telson posterior margin convex with 6 pairs spines and 1 pair mesial setae, less than posterior margin of uropod . . . . . A. brevitelsonis

Kikuchi and Hashimoto, 2000 [Minami Ensei Knoll, Okinawa Trough, 705 m]

– Rostrum 6 or less teeth; telson posterior margin slightly sinusoidal or concave mesially

(i.e. notched appearance) and at or greater than the posterior margin of uropod . . . 7

7. Antennal scale 2.2-2.6 times longer than wide; telson posterior margin slightly sinusoidal to shallowly concave (i.e. notched)...... A. lusca

Williams and Chace, 1982 [Galápagos Rift, 9ºN East Pacific Rise, 2400–2600 m]

– Antennal scale 1.6-2.1 times longer than wide; telson distinctly concave (i.e. notched) mesially; stylocerite reaching 2nd antennular peduncle segment . . . . . A. komaii sp. nov.

This Study [Eastern-Lau Spreading Center, 1800-2700 m]

8. Rostrum usually unarmed on ventral margin ...... 9

– Rostum always armed on ventral margin ...... 10

9. Second segment of antennular peduncle about 1.1–1.2 times as long as wide; telson length 2.2–2.5 times as long wide anteriorly ...... A. williamsi

Shank and Martin, 2003 [Menez Gwen, Mid-Atlantic Ridge, 850 m]

– Second segment of antennular peduncle about 1.8 times as long as wide; telson length about 2.9 times as long as wide anteriorly ...... A. niwa

Webber, 2004 [New Zealand volcanic seamounts, 367-1346 m]

10. Rostrum with less than 3 ventral teeth; pterygostomian tooth not strongly produced anteriorly; second segment of antennular peduncle 1.4–1.5 times longer than wide......

...... A. dissimilis 39 Komai and Segonzac, 2005[Minami Ensei Knoll, Okinawa Trough, 705 m]

– Rostrum usually with more than 3 ventral teeth; pterygostomian tooth of carapace strongly produced anteriorly; distolateral tooth of antennal scale usually with straight mesial margin ...... 11

11. Anterior part of branchial region somewhat inflated, strongly convex; post-antennal groove deep; telson length greater than 2.9 telson anterior width ...... 12

– Anterior part of branchial region not particularly inflated, only slightly convex; post- antennal groove shallow; telson length less than 2.9 telson anterior width ...... 13

12. Telson at or greater than posterior margin of uropod; posterior-most tooth of dorsal rostral series arising from 0.34–0.40 of carapace length; second segment of antennular peduncle 1.9–2.1 times longer than wide; antennal scale 1.9–2.1 times longer than wide

...... A. muricola

Williams, 1988 [Florida Escarpment, Gulf of Mexico, 3277 m; Barbados

Accretionary Prism, 1697 m; West Equatorial African Margin, 3150 m]

– Telson slightly less than posterior margin of uropod; posterior-most tooth of dorsal rostral series arising from 0.21-0.34 of carapace length; second segment of antennular peduncle 1.35-1.95 times longer than wide; antennal scale 1.7-1.85 times longer than wide ...... A. methanophila

Komai et al., 2005 [Blake Ridge Diapir, 2155-2167 m]

13. Rostrum usually not reaching distal margin of antennular peduncle; posterior-most tooth of dorsal rostral series arising from 0.24–0.31 of carapace length; second segment of antennular peduncle 1.8–2.05 times longer than wide; antennal scale 1.91–2.04 times longer than wide ...... A. markensis 40 Williams, 1988 [Lucky Strike to Ashadze, Mid-Atlantic Ridge, 1693–3650 m]

– Rostrum reaching or overreaching distal margin of antennular peduncle, posterior-most tooth of dorsal rostral series arising from 0.38–0.48 of carapace length; second segment of antennular peduncle 1.58–1.69 times longer than wide; antennal scale 1.72–1.9 times longer than wide ...... A. longirostris

Kikuchi and Ohta, 1995 [Okinawa Trough, 1053–1627 m; Off Hatsushima site,

Sagami Bay, 1120–1220 m; Brothers Caldera, New Zealand, 1196-1810 m]

14. Antennal scale, bases of antennae, and stylocerite closely approximated, forming opercular complex shielding mouthparts; carapace greatly inflated with dorsal “eyespot”; rostrum greatly reduced; eyes greatly modified, forming ocular plate . . . Rimicaris 15

– Antennal scale, bases of antennae, and stylocerite not closely approximated; carapace not greatly inflated; rostrum reduced but distinct; ocular plates fused mesially, but not forming ocular plate ...... 16

15. Carapace without setae...... Rimicaris kairei

Watabe and Hashimoto, 2002 [Kairei Field, Central Indian Ridge, 2454 m]

– Carpace ornamented with tufts of setae...... Rimicaris exoculata

Williams and Rona, 1986 [TAG, Mid-Atlantic Ridge, 3620-3650 m]

16. Strap-like epipods on third maxilliped and pereopods 1-4 ...... Mirocaris 17

– No strap-like epipods on third maxilliped and pereopods ...... 18

17. Submarginal setae on faces of fingers on first chelae ...... Mirocaris fortunata

Martin and Christiansen, 1995 [14ºN-38ºN, Mid-Atlantic Ridge, 850-3650 m]

– No submarginal setae on faces of fingers on first chelae ...... Mirocaris indica

Komai et al., 2006 [Central Indian Ridge, 2422-3300 m] 41 18. Rostrum with minute ‘denticles’ or unarmed, outer ramus of uropod with 1 movable spine at posterodistal corner...... Opaepele 21

– Rostrum without teeth, terminating bluntly; outer ramus of uropod with 2 movable spines posterodistal corner ...... Chorocaris* 19

19. Branchiostegal angle of carapace unpronounced, nearly straight; rostrum reaching but not exceeding postorbital prominences ...... Chorocaris chacei

(Williams and Rona, 1986) [14ºN-38ºN, Mid-Atlantic Ridge, 850-3650 m]

– Branchiostegal angle of carapace rising from about 30º from horizontal; rostrum clearly exceeding postorbital prominences ...... 20

20. Anterolateral tooth of antennal scale reduced, blunt, following lateral margin of antennal scale ...... Chorocaris vandoverae

Martin and Hessler, 1990 [Mariana, 3595-3660 m; Lau Basin, 1750-2750 m]

– Anterolateral tooth of antennal scale acute, directed forward and laterally away from margin of antennal scale ...... Chorocaris paulexi

Martin and Shank, 2005 [South East Pacific Rise, 2573-2832 m]

21. Rostrum armed with up to 6 minute denticles dorsally, weakly carinate dorsally, tip acuminate ...... Opaepele loihi

Williams and Dobbs, 1995 [Loihi Seamount, Hawaii, 980 m]

– Rostrum unarmed, without dorsal carina, tip rounded or subtruncate ......

...... Opaepele susannae

Komai et al. In Press [South Mid-Atlantic Ridge 4°-10°S, 1500-2986 m]

* Species in the genus Chorocaris is difficult to distinguish based on morphology alone.

42 Acknowledgements

This work would not be possible without the skill and dedication of the captains and crews of the R/V Melville and the crew of the ROV JASON II 2005 (TUIM07MV) and 2006 (MGLN07MV) cruises. The chief scientist, Dr. Charles Fisher, provided us with space on both cruises and access to specimens. We thank the Kingdom of Tonga for permitting collection in their waters. The map in Fig. 1 was prepared with assistance from

Liz Podowski. Adriana Gaytán Caballero reviewed the dichotomous key. Michel

Segonzac provided valuable comments on an earlier draft which greatly improved this paper as well providing samples of Alvinocaris muricola from the Gulf of Guinea for

DNA analysis. We thank Christopher Boyko, Tim Shank and an anonymous reviewer for their thoughtful comments. This work was funded by NSF Grant OCE 003403953 to Dr.

Fisher and S.H.

Notes

Stéphane Hourdez is a coauthor on the publication of this chapter and assisted in editing the manuscript. Stéphane Hourdez assisted with the description, making line drawings and in the molecular analysis. This chapter is published in 2009 in the

Proceedings of the Biological Society of Washington Volume 122, Issue 1, pages 52-71.

Literature Cited

Beck, L. A. 1992. Two new neritacean limpets (Gastropoda: Prosobranchia: Neritacea:

Phenacolepadidae) from active hydrothermal vents at Hydrothermal Field 1 43 "Wienerwald" in the Manus Back-Arc Basin (Bismarck Sea, Papua-New Guinea).

Annals des Naturhistorischen Museums in Wien, ser. B 93:259-275.

------. 1993. Morphological and anatomical studies on a new lepetodrilacean limpet

(Gastropoda, Prosobranchia) from hydrothermal vents at the Manus Back-Arc

Basin (Bismarck Sea, Papua New Guinea). Annals des Naturhistorischen

Museums in Wien, ser. B 94/95:167-179.

Black, M. B., K. Halanych, P. Maas, W. R. Hoeh, J. Hashimoto, D. Desbruyères, R. Lutz,

and R. C. Vrijenhoek. 1997. Molecular systematics of deep-sea tubeworms

(Vestimentifera). Marine Biology 130:141-149.

Bouchet, P., & A. Warén. 1991. Ifremeria nautilei, a new gastropod from hydrothermal

vents, probably associated with symbiotic bacteria. Comptes Rendus de

l'Academie des Sciences Série III 312:495-501.

Christoffersen, M. L. 1986. Phylogenetic relationships between Oplophoridae, Atyidae,

Pasiphaeidae, Alvinocarididae fam. n., Bresiliidae, Psalidopodidae and

Disciadidae (Crustacea Caridea Atyoidea). Boletim de Zoologia 10:273-281.

Cordes, E. C., S. L. Carney, S. Hourdez, R. S. Carney, J. M. Brooks and C. R. Fisher

(2007). Cold seeps of the deep Gulf of Mexico: Community structure and

biogeographic comparisons to Atlantic equatorial belt seep communitie.s Deep-Sea

Res. I 54: 637-653. de Saint Laurent, M. 1984. Crustacea Decapoda from the hydrothermal vents of the East

Pacific Rise at 13°N, collected during the french Biocyatherm Expedition.

Comptes Rendus de l'Academie des Sciences Série III 299:355-360. 44 de Saint Laurent, M., & E. MacPherson. 1997. Une nouvelle espèce du genre Paralomis

White, 1856, des sources hydrothermales du sud-ouest Pacifique (Crustacea,

Decapoda, Lithodidae). Zoosystema 19:721-727.

Desbruyères, D., A.-M. Alayse-Danet, S. Ohta, & Scientific Parties of BIOLAU and

STARMER cruises. 1994. Deep-sea hydrothermal communities in Southwestern

Pacific back-arc basins (the North Fiji and Lau Basins): composition,

microdistribution and food web. Marine Geology 116:227-242.

Escobar-Briones, E., & J. L. Villalobos-Hiriart. 2003. Deep-water caridean shrimps

(Crustacea: Decapoda) from Banco Chinchorro and adjacent areas in the northern

Caribbean. Bulletin of Marine Science 73:99-122.

Folmer, O. O., M. M. Black, W. W. Hoeh, R. R. Lutz, & R. R. Vrijenhoek. 1994. DNA

primers for amplification of mitochondrial cytochrome c oxidase subunit I from

diverse metazoan invertebrates. Molecular marine biology and biotechnology

3:294-299.

Guinot, D. 1989. Austinograea alayseae sp. nov., crabe hydrothermal découvert dans le

bassin de Lau, Pacifique sud-occidental (Crustacea Decapoda Brachyura).

Bulletin de Museum National Histoire Naturelle, Paris (sér 4) 11:879-903.

Hessler, R. R., & J. W. Martin. 1989. Austinograea williamsi, new genus, new species, a

hydrothermal vent crab (Decapoda: Bythograeidae) from the Mariana Back-Arc

Basin, Western Pacific. Journal of Crustacean Biology 9:645-661.

Kikuchi, T., & S. Ohta. 1995. Two caridean shrimp of the families Bresiliidae and

Hippolytidae from a hydrothermal field on the Iheya Ridge, off the Ryukyu

Islands, Japan. Journal of Crustacean Biology 15:771-785. 45 Kikuchi, T., & J. Hashimoto. 2000. Two new caridean shrimps of the family

Alvinocarididae (Crustacea,Decapoda) from a hydrothermal field at the Minami-

Ensei Knoll in the Mid-Okinawa Trough, Japan. Species Diversity 5:135-148.

Komai, T., & M. Segonzac. 2003. Review of the hydrothermal vent shrimp Mirocaris,

redescription of M. fortunata and reassessment of the taxonomic status of the

family Alvinocarididae (Crustacea: Decapoda: Caridea). Cahiers Biologie Marine

44:199-215.

------. 2004. A new genus and species of alvinocarid shrimp (Crustacea: Decapoda:

Caridea) from hydrothermal vents on the North Fiji and Lau Basins, south-

western Pacific. Journal of the Marine Biological Association of the UK 84:1179-

1188.

------. 2005. A revision of the genus Alvinocaris Williams and Chace (Crustacea:

Decapoda: Caridea: Alvinocarididae), with descriptions of a new genus and a new

species of Alvinocaris. Journal of Natural History 39:1111-1175.

Komai, T., T. M. Shank, & C. L. Van Dover. 2005. A new species of Alvinocaris

(Crustacea: Decapoda: Caridea: Alvinocarididae) and a new record of A. muricola

from methane seeps on the Blake Ridge Diapir, northwestern Atlantic. Zootaxa

1019:27-42.

Komai, T., O. Giere, & M. Segonzac. In Press. New records of alvinocaridid shrimps

(Crustacea: Decapoda: Caridea) from hydrothermal vent fields on the southern

Mid-Atlantic Ridge, including a new species of the genus Opaepele.

Komai, T., J. W. Martin, K. Zala, S. Tsuchida, & J. Hashimoto. 2006. A new species of

Mirocaris (Crustacea: Decapoda: Caridea: Alvinocarididae) associated with 46 hydrothermal vents on the Central Indian Ridge, Indian Ocean. Scientia Marina

70:109-119.

Martin, J. W., & R. R. Hessler. 1990. Chorocaris Vandoverae, a New Genus and Species

of Hydrothermal Vent Shrimp (Crustacea, Decapoda, Bresiliidae) from the

Western Pacific. Contributions in Science 417:1-11.

Martin, J. W., & J. C. Christiansen. 1995. A new species of the shrimp genus Chorocaris

Martin & Hessler, 1990 (Crustacea: Decapoda: Bresilidae) from hydrothermal

vent fields along the Mid-Atlantic Ridge. Proceedings of the Biological Society of

Washington 108:220-227.

Martin, J. W., & T. Shank. 2005. A new species of the shrimp genus Chorocaris

(Decapoda: Caridea: Alvinocarididae) from hydrothermal vents in the eastern

Pacific Ocean. Proceedings of the Biological Society of Washington 118:183-198.

Martin, J. W., & T. A. Haney. 2005. Decapod crustaceans from hydrothermal vents and

cold seeps: a review through 2005. Zoological Journal of the Linnean Society

145:445-522.

Miura, T., & D. Desbruyères. 1995. Two new species of Opisthotrochopodus

(Polychaeta: Polynoidae: Branchinotogluminae) from the Lau and North Fiji

back-arc basins, southwestern Pacific Ocean. Proceedings of the Biological

Society of Washington 108:583-595.

Okutani, T., & S. Ohta. 1988. A new gastropod mollusk associated with hydrothermal

vents in the Mariana Back-Arc Basin, Western Pacific. Venus (Japan Journal of

Malacology) 47:1-9.

Ondréas, H., K. Olu, Y. Fouquet, J. L. Charlou, A. Gay, B. Dennielou, J. P. Donval, A. 47 Fifis, T. Nadalig, P. Cochonat, E. Cauquil, J. F. Bourillet, M. Le Moigne, M. Sibuet

2005. ROV study of a giant pockmark on the Gabon continental margin. Geo-

Marine Letters, 25, 281-292.

Ramirez-Llodra, E., & M. Segonzac. 2006. Reproductive biology of Alvinocaris muricola

(Decapoda: Caridea: Alvinocarididae) from cold seeps in the Congo Basins.

Journal of the Marine Biological Association of the UK 86:1347-1356.

Segonzac, M., M. de Saint Laurent, & B. Casanova. 1993. L'énigme du comportement

trophique des crevettes Alvinocarididae des sites hydrothermaux de la dorsale

médio-atlantique. Cahiers Biologie Marine 34:535-571.

Shank, T. M., & J. W. Martin. 2003. A new caridean shrimp of the family

Alvinocarididae from thermal vents at Menez Gwen on the Mid-Atlantic Ridge.

Proceedings of the Biological Society of Washington 116:158-167.

Shank, T. M., M. B. Black, K. M. Halanych, R. A. Lutz, & R. C. Vrijenhoek. 1999.

Miocene radiation of deep-sea hydrothermal vent shrimp (Caridea:Bresilidae):

evidence from mitochondrial cytochrome oxidase subunit I. Molecular

Phylogenetics and Evolution 13:244-254.

Tyler, P. A., & C. M. Young. 1999. Reproduction and dispersal and vents and cold seeps.

Journal of the Marine Biological Association of the UK 79:193-208.

Van Dover, C. L., P. Aharon, J. M. Bernhard, E. Caylor, M. Doerries, W. Flickinger, W.

Gilhooly et al. 2003. Blake Ridge methane seeps: characterization of a soft-

sediment, chemosynthetically based ecosystem. Deep-Sea Research I 50:281-300. 48 Vereshchaka, A. L. 1997. A new family for a deep-sea caridean shrimp from north

Atlantic hydrothermal vents. Journal of the Marine Biological Association of the

UK 77:425-428. von Cosel, R., B. Métivier, & J. Hashimoto. 1994. Three new species of Bathymodiolus

(Bivalvia: Mytilidae) from hydrothermal vents in the Lau Basin and the North Fiji

Basin, Western Pacific, and the Snake Pit Area, Mid-Atlantic Ridge. The Veliger

37:374-392.

Warén, A., & P. Bouchet. 1993. New records, species, genera, and a new family of

gastropods from hydrothermal vents and hydrocarbon seeps. Zoologica Scripta

22:1-90.

Watabe, H., & J. Hashimoto. 2002. A new species of the genus Rimicaris

(Alvinocarididae: Caridea: Decapoda) from the active hydrothermal vent field,

"Kairei Field," on the Central Indian Ridge, the Indian Ocean. Zoological Science

19:1167-1174.

Webber, W. R. 2004. A new species of Alvinocaris (Crustacea: Decapoda:

Alvinocarididae) and new records of alvinocaridids from hydrothermal vents

north of New Zealand. Zootaxa 444:1-26.

Williams, A. B. 1988. New marine decapod crustaceans from waters influenced by

hydrothermal discharge, brine, and hydrocarbon seepage. Fishery Bulletin

86:263-287.

Williams, A. B., & F. A. Chace. 1982. A new caridean shrimp of the family Bresiliidae

from thermal vents of the Galapagos Rift. Journal of Crustacean Biology 2:136-

142. 49 Williams, A. B., & P. A. Rona. 1986. Two new caridean shrimps (Bresiliidae) from a

hydrothermal field on the Mid-Atlantic Ridge. Journal of Crustacean Biology

6:446-462.

Williams, A. B., & F. C. Dobbs. 1995. A new genus and species of caridean shrimp

(Crustacea: Decapoda: Bresiliidae) from hydrothermal vents on Loihi Seamount,

Hawaii. Proceedings of the Biological Society of Washington 108:228-237.

Yamaguchi, T., & W. A. Newman. 1990. A new and primitive barnacle (Cirripedia:

Balanomorpha) from the North Fiji basin abyssal hydrothermal field, and its

evolutionary implications. Pacific Science 44:135-155.

50 CHAPTER 2

Hexacorals (Anthozoa: Actiniaria, Zoanthidea) from hydrothermal vents in the South-

western Pacific

Abstract

Four new species of sea anemones are described from the Eastern Lau Spreading

Center, with notes on three additional Hexacorallia. Cyananthea hourdezi n. sp. and

Alvinactis chessi n. sp. (Actinoscyphiidae) extend the range of the two previously monotypic, vent endemic genera from the East Pacific Rise. Chondrophellia orangina n. sp. (Hormathiidae) is the third species of its genus; it inhabits both hydrothermal vents and non-venting sites. Similarly, Sagartiogeton erythraios n. sp. (Sagartiidae) was collected from non-vent settings, but is documented on video from near diffuse-flow hydrothermal vents. In addition, we report two species from families Actinostolidae and

Hormathiidae whose identity could not be established based on the existing material, and provide the first record of a member of order Zoanthidea from a hydrothermal vent. The ecological context of the sites at the Eastern Lau Spreading Center containing sea anemones is described.

Introduction

Since their discovery thirty years ago (Corliss et al. 1979), biological communities at chemosynthetic communities such as hydrothermal vents (Desbruyères et al. 2006b; Fisher et al. 2007b), methane seeps (Fisher et al. 2007a; Levin 2005), and whale falls (Smith and Baco 2003), have proven to be a rich source of new species.

Hydrothermal vent ecosystems are based primarily on energy derived from hydrogen 51 sulfide, and are anchored by invertebrates (e.g., tubeworms, mussels, clams, gastropods, etc.) containing endosymbiotic bacteria capable of oxidizing sulfide to sulfate (Nelson and Fisher 1995). These invertebrates also provide habitat for a variety of other fauna

(Govenar and Fisher 2007).

Sea anemones (Cnidaria: Anthozoa: Actiniaria) are common and conspicuous inhabitants of many hydrothermal vent ecosystems in the Atlantic, Pacific, and Indian

Oceans. Four families of actiniarians have been reported from hydrothermal vent ecosystems: Actinoscyphiidae, Actinostolidae, Hormathiidae, and Kadosactidae. The first chemosynthetic actiniarians were described by Doumenc and Van Praët (1988) from the

East Pacific Rise. Subsequent discoveries were made from hydrothermal vents at the

Marianas Trough (Fautin and Hessler 1989), Mid-Atlantic Ridge (Fautin and Barber

1999), Guaymas Basin (López-González et al. 2003), Manus Basin (López-González et al. 2005), and again at the East Pacific Rise (Daly 2006; Sanamyan and Sanamyan 2007;

Rodríguez et al. in review). Records of anthozoans from other deep-sea chemosynthetic environments are sparser. One species of zoanthid has been described from a methane seep in Japan (Reimer et al. 2007), while only a handful of anthozoans were found at various seeps localities (López-González et al. 2003; Sanamyan and Sanamyan 2007).

Daly and Gusmão (2007) described the only sea anemone reported from a chemoautotrophic community at a whale fall.

We report four new species of sea anemones and the fifth actiniarian family from hydrothermal vent communities at the Eastern Lau Spreading Center (ELSC). The ELSC is situated in a back-arc basin in the waters of Fiji and Tonga. According to the boundaries of Tyler et al. (2003), the ELSC is located in a biogeographic province 52 encompassing western Pacific back-arc basins from Japan to New Zealand. The new species of sea anemones we describe extend the range of the previously monotypic genera Cyananthea Doumenc and Van Praët, 1988, and Alvinactis Rodríguez, Castorani and Daly, in review, from the eastern Pacific Ocean mid-ocean ridges. Our new species of Sagartiogeton Carlgren, 1924, is the first member of its genus or family to be recorded from hydrothermal vents. Moreover, we include notes on two additional species of sea anemone and one species of Zoanthidea for which either the material available was insufficient or the taxonomy of the groups to which they belong is too uncertain for us to identify them to species.

FIGURE 1. Map of collection

sites at the Lau Basin with

topographic features, see text

for details. Background image

is courtesy of the Ridge

Multibeam Synthesis Data

Portal of the Marine

Geoscience Data System.

53 Materials and Methods

Specimens were collected during the June 2005 TUIM07MV and September 2006

MGLN07MV cruises to the ELSC aboard the R/V Melville. Collection used the manipulator arm and suction sampler of Remotely Operated Vehicle JASON II.

Specimens came from the following sites (Fig. 1): Kilo Moana (20°9’S, 176°12’E, 2620 m depth), TowCam (20°19’S, 176°8’E, 2700 m depth), ABE (20°45’S, 176°11’E, 2145 m depth), and Tu’i Malila (21°59’S, 176°34’E, 1880 m depth).

Specimens were removed from rock grabs, suction sampler holsters, and mussel shells by hand, placed in chilled water, and allowed to relax before being anaesthetized with isotonic magnesium chloride. These specimens were then fixed in 10% seawater buffered formalin for at least 48 hours before being transferred to 70% ethanol for long- term storage.

Formalin-fixed specimens were examined whole, in dissection, and as serial sections. Serial sections were prepared using standard paraffin techniques. Histological slides were stained in Masson’s trichrome (Presnell and Schreibman 1997). Pieces of tissue from pedal disc, tentacles, column, mesenterial filaments, actinopharynx, and acontia (when present) were smeared on a slide; cnidae in these smears were examined using DIC microscopy at 100X magnification. Cnida terminology follows Mariscal

(1974). Specimens have been deposited at the Field Museum of Natural History (FMNH) and the U. S. National Museum of Natural History (USNM).

54 Results and Discussion

Order Actiniaria Hertwig, 1882

Suborder Nynantheae Carlgren, 1899

Family Actinoscyphiidae Stephenson, 1920

Genus Cyananthea Doumenc and Van Praët, 1988

Definition. Actinoscyphiidae with broad, adherent pedal disc. Column smooth, not clearly divided into scapus and scapulus. Cinclides present at least in stronger endocoels. Marginal sphincter muscle mesogleal, strong. Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal to meso-ectodermal. Mesenteries more numerous distally than proximally, hexamerously arranged, first two cycles perfect.

Two pairs of directives, each attached to siphonoglyph. All stronger mesenteries fertile.

Retractor muscles diffuse. Acontia absent. Cnidom: Robust and gracile spirocysts, basitrichs, holotrichs (heterotrichs), and microbasic p-mastigophores (modified from

Sanamyan and Sanamyan (2007); differences between p-mastigophores A and B not included because of the difficulty distinguishing the capsules when undischarged; changes in italics).

Type species. Cyananthea hydrothermala Doumenc and Van Praët, 1988, by monotypy.

Cyananthea hourdezi n. sp.

Figs. 2-4, Table 1

Diagnosis. Living specimens trumpet-shaped, with white column and moderately short, bluntly conical deep red to light pink tentacles that lack aboral thickenings. 55 Column of preserved, contracted specimens smooth, dome-like, diameter of base 29-36 mm, height 24-30 mm, with distal belt of up to 24 cinclides. Tentacles with abundant microbasic p-mastigophores and spirocysts, holotrichs present but not abundant.

Mesenteries hexamerously arranged, first two cycles perfect.

Etymology. Named for Stéphane Hourdez in recognition of his contributions to the study of the biology of hydrothermal vent animals.

Material examined. USNM #####: Kilo Moana, dive J2-235, 16 September

2006, one specimen; USNM #####: TowCam, dive J2-240, 29 September 2006, four specimens; USNM #####: Kilo Moana, dive J2-230, 06 September 2006, one specimen.

FMNH ####: ABE, dive J2-128-4-B5, 12 April 2005, one specimen; FMNH ####: Kilo

Moana, dive J2-154, 11 June 2005, one specimen.

Oral disc and tentacles. Oral disc flat, with broad, tentacle-free space surrounding slit-like mouth; mouth elevated on conical hypostome, with two prominent siphonoglyphs. Lips and siphonoglyphs white, actinopharynx pink to red. Distal column covers oral disc and tentacles in contraction so only tips of tentacles visible (Figs. 2A,B).

Approximately 100 tentacles in six crowded marginal cycles, those of inner cycles longer than those of outer cycle (Figs. 2D,E). Tentacles blunt, length in contraction less than oral disc radius; in life, tentacles longer and more sharply tapering, those of inner cycle approximately equal in length to oral disc diameter (Fig. 2E). In life, tentacles red to pink, occasionally white, those of inner cycles typically held erect, those of outer cycle held out or pointing towards substrate (Fig. 2D). Tentacles of preserved specimens same color as column or slightly pinker; color differences more pronounced in living 56 specimens. Longitudinal musculature of tentacles ectodermal (Fig. 3F).

FIGURE 2. Cyananthea hourdezi n. sp. External anatomy: A, and B, preserved specimens; C, detail of distal row of cinclides; D, Living specimens; E, expanded living specimen. Scale bars: A, B, 20 mm; C, 1 mm; E, 40 mm.

Base and column. Column dome-shaped, smooth, in preserved, contracted specimens (Figs. 2A,B), height to 30 mm, diameter to 36 mm. In life, column flares slightly from base (Fig. 2E). Column not obviously differentiated into scapulus and scapus, but some specimens have small particles adhering only to lower column. Distal belt of inconspicuous perforate cinclides (Figs. 2C, 3E) in stronger endocoels, usually 12-

24 in number, but more than 24 in one specimen. Column of preserved specimens cream 57 to tan; column of living specimens opaque pale pink. No fosse; distal edge of column may extend over base of tentacles in contracted specimens. Column musculature strong, with strong, long mesogleal marginal sphincter; sphincter encompassing most of the mesoglea distally, tapering proximally (Fig. 3A), closer to gastrodermis than epidermis, with many large lacunae (Fig. 3C).

Pedal disc adherent, muscular, flat or slightly withdrawn inside column in preserved specimens, same color as column. Diameter of pedal disc approximately equal or slightly wider than oral disc in preserved, contracted specimens (Figs. 2A,B), equal to or slightly smaller than oral disc in living specimens (Fig. 2E). Basilar musculature well developed (Fig. 3G).

FIGURE 3 (next page). Cyananthea hourdezi n. sp. Internal anatomy: A, longitudinal section through distal column, showing mesogleal marginal sphincter (between arrows);

B, cross section of the mesenteries at actinopharynx, showing mesenteries from first to fourth cycle (numbers indicate the different cycles); C, detail of the marginal sphincter muscles fibers embedded in the mesoglea; D, cross section thorough mesenteries below actinopharynx showing diffuse retractor muscles; E, longitudinal section through distal column showing a cinclide; F, cross section through a tentacle showing longitudinal ectodermal muscles; G; cross section of the pedal disc showing basilar muscles (arrows).

Scale bars: A, 0.5 mm; B, 1 mm; C, 0.1 mm; D, 1 mm; E, 0.5 mm; F, 0.05 mm; G, 0.02 mm. 58

59 Mesenteries and internal anatomy. Mesenteries arranged hexamerously in five cycles, those of first two cycles perfect. Fifth cycle incomplete, more developed distally, thus more mesenteries distally than proximally. Two pairs of directives, each attached to siphonoglyph (Fig. 3B). All mesenteries of first three cycles including directives fertile, bear filaments; those of four and fifth cycles weak, without filaments or gametogenic tissue (Fig. 3B). All examined specimens male, fertile, spermatic vesicles 0.09-0.29 mm in diameter.

Longitudinal muscles of mesenteries weak (Figs. 3B,D). Retractor muscles diffuse, wide, spanning first two-thirds of distance between body wall and filament and bearing short, relatively thick branches (Fig. 3D). Parietobasilar muscles weakly differentiated from mesenterial lamella, consisting of few short processes with no pennon

(Fig. 3D).

Cnidom. Robust and gracile spirocysts, basitrichs, holotrichs, microbasic p- mastigophores (Fig. 4). See Table 1 for size and distribution.

FIGURE 4 (next page). Cyananthea hourdezi n. sp. Cnidae: A, basitrich; B, basitrich; C, microbasic p-mastigophore; D, basitrich; E, microbasic p-mastigophore; F; robust spirocyst; G, basitrich; H, microbasic p-mastigophore; I, holotrich; J, basitrich; K, microbasic p-mastigophore; L, basitrich; M, microbasic p-mastigophore. 60

61 Table 1. Summary of size ranges of cnidae of Cyananthea hourdezi n. sp. x¯ : mean length by mean width of capsules. SD: standard deviation. S: ratio of number of specimens in which each type was found to number of specimens examined. N: total number of capsules measured. F: frequency: +++ = very common, ++ = common, + = less common, --- = sporadic.

Range of length C. hydrothermala (Sanamyan Category and width of capsules x¯ ± SD S N F and Sanamyan 2007) S (!m) PEDAL DISC Basitrichs — 0/4 12-14 x 2 2/2 Basitrichs 15.2-28.1 x 1.4-3.8 22.6 ±2.9 x 2.7 ± 0.4 4/4 56 +/++ 16-26 x 2-3 2/2 SCAPUS Basitrichs 20.6-27.8 x 2.1-3.7 24.4 ±1.5 x 2.9 ± 0.3 4/4 65 ++/+++ 19-25 x 2-3 2/2 Microbasic p-mastigophores 22.9-31.2 x 3.8-5.4 25.8 ±1.6 x 4.6 ± 0.4 4/4 54 +/++ — 0/2 MARGIN Basitrichs 22.6-34.4 x 1.4-4.0 27.3 ±3.0 x 3.1 ± 0.5 3/3 45 ++/+++ 18-27 x 2-3 2/2 Microbasic p-mastigophores 26.3-37.3 x 3.8-6.1 30.2 ±2.6 x 5.0 ± 0.7 3/3 45 ++/+++ 20-26 x 4-5.5 2/2 TENTACLES BASE Robust spirocysts(1) 26.4-61.9 x 2.6-9.2 42.1 ±8.5 x 6.3 ± 1.7 5/6 40 +/++ 19-70 x 3.5-9 3/3 Gracile spirocysts — 22-45 x 2.5-4.5 3/3 Basitrichs 26.9-40.1 x 1.8-3.9 33.1 ±2.9 x 2.7 ± 0.5 5/6 40 ++ 20-35 x 2-3.5 3/3 Microbasic p-mastigophores(3) 29.1-39.6 x 3.8-6.3 33.5 ±2.8 x 5.2 ± 0.6 6/6 47 +++ 22-38 x 3.5-6 3/3 Holotrichs(2,4) 31.7-46.3 x 5.9-8.4 39.7 ±3.3 x 6.7 ±1.0(*) 5/6 27 +/++ 39-72 x 4-7 2/2 ACTINOPHARYNX Basitrichs — 0/4 12-19 x 2-2.5 3/3 Basitrichs 24.1-40.1 x 2.1-3.9 30.8 ±3.7 x 3.0 ± 0.3 3/4 46 ++ 27-37 x 2-3 3/3 Microbasic p-mastigophores(1) 28.1-39.2 x 3.2-5.6 34.1 ±1.7 x 4.2 ± 0.7 4/4 66 ++/+++ 22-24 x 3.5 3/3 Microbasic p-mastigophores 26-36 x 2.5-5 2/3 FILAMENTS Basitrichs 12.6-19.9 x 1.3-2.9 15.9 ±1.7 x 2.3 ± 0.3 3/4 41 +/++ 12-20 x 2-2.5 3/3 Basitrichs — 0/4 26-35 x 2.5-3 3/3 Microbasic p-mastigophores(5) 31.8-40.7 x 3.2-5.1 36.4 ±1.9 x 4.2 ± 0.5 4/4 66 +++ 26-40 x 3.5-5 3/3 Microbasic p-mastigophores — 0/4 25-37 x 4-5 2/3 Holotrichs(2) — 0/4 36-45 x 4.5-6.5 2/3

(*) Average based measurements of fewer than 40 capsules; the measurement of at least 40 capsules is usually considered minimum for statistical significance (Williams, 1998; 2000). (1) Sanamyan and Sanamyan (2007) differentiated the spirocysts into gracile and robust, but we could not distinguish the two consistently. (2) Sanamyan and Sanamyan (2007) called these cnidae heterotrichs. (3) Sanamyan and Sanamyan (2007) only found this type at the base of the tentacles. (4) Sanamyan and Sanamyan (2007) only found this type in the tips of the tentacles. (5) Sanamyan and Sanamyan (2007) differentiated this type of microbasic p-mastigophores into two types also present in our material, but we could not distinguish the two consistentl 62 Taxonomic remarks. Cyananthea hourdezi n. sp. is the second species attributed to this genus, which is comprised entirely of species living in chemosynthetically active deep- sea habitats. Cyananthea hourdezi n. sp. has all of the attributes ascribed to the genus in a recent re-description of C. hydrothermala (Sanamyan and Sanamyan 2007). Cyananthea hourdezi n. sp. can be distinguished from C. hydrothermala based on anatomy and cnidom. The mesenteries, retractor muscles, and parietobasilar muscles differ between the species (Figs. 3B,D and Fig. 10 in Sanamyan and Sanamyan 2007). In C. hourdezi n. sp., the mesenteries and retractor muscles are very delicate, with thin mesoglea; the parietobasilar muscles lack a distinct pennon but are differentiated (Fig. 3D). In contrast, in C. hydrothermala, the mesenteries are more robust, with thicker mesoglea, and the parietobasilar muscles are hardly discernible (Sanamyan and Sanamyan 2007: Fig. 10).

Unlike C. hydrothermala, C. hourdezi n. sp. has microbasic p-mastigophores in the scapus and lacks holotrichs and a second larger size class of basitrichs in the mesenterial filaments. The basitrichs and microbasic p-mastigophores of the distal column margin are larger in C. hourdezi n. sp. than in C. hydrothermala. The basitrichs of the actinopharynx in C. hydrothermala include a small size class absent from C. hourdezi n. sp. The size differences are not unidirectional: the holotrichs of the tentacles are larger in C. hydrothermala than in C. hourdezi n. sp. Furthermore, both species of Cyananthea differ in geographic distribution: C. hydrothermala has been reported from several hydrothermal sites in the northeastern Pacific (Sanamyan and Sanamyan 2007), whereas

C. hourdezi n. sp. is from the southwestern Pacific.

Cyananthea is similar to the genus Pacmanactis López-González, Rodríguez and

Segonzac, 2005 in many respects (see Rodríguez et al. in review); Cyananthea hourdezi, 63 in particular, resembles the type species Pacmanactis hashimotoi López-González,

Rodríguez and Segonzac, 2005, as the two have the same number of perfect mesenteries.

However, unlike Cyananthea, Pacmanactis has the same number of mesenteries distally and proximally, a difference accorded significance as a generic-level character in some groups of Actiniaria (e.g., Hormathiidae; see Carlgren 1949). Moreover, in Pacmanactis the cinclides are associated with verrucae, but verrucae are absent in C. hourdezi n. sp.

Verrucae are a generic feature in other Actiniaria (e.g., Actiniidae; see Carlgren 1949).

We consider verrucae more important taxonomically than the number of mesenteries proximally and distally, at least in Mesomyaria (Rodríguez et al. in review). The relative number of mesenteries reflects the way in which mesenteries develop, and, although this feature may have value, it can be difficult to assess in animals that are no longer adding mesenteries, and may vary in expression or perceived importance with the size of the animal. It varies within mesomyarian genera (e.g., Anthosactis, Bathydactylus; see

Carlgren 1956; Daly and Gusmão 2007), and is unreported in the diagnoses of most genera (Carlgren 1949). In contrast, verrucae are visible regardless of size, their occurrence is relatively unusual outside of endomyarian families, and they are remarked upon in the diagnoses of all mesomyarian genera in which they occur (e.g., Sanamyan and Sanamyan 2007; Rodríguez et al. in review).

Genus Alvinactis Rodríguez, Castorani and Daly, in review

Definition. Actinoscyphiidae with broad, adherent pedal disc. Column smooth, not divisible into scapus and scapulus, with distal row of cinclides associated with 64 verrucae or papillae. Distal margin of column distinctly marked as a marginal ring.

Tentacles of uniform thickness along entire length, those of inner cycle longer than those of outer cycle. Longitudinal muscles of tentacles ectodermal, equally developed.

Mesenteries arranged in four cycles; same number proximally and distally, only first cycle perfect. All mesenteries except those of youngest cycle fertile. Two well-developed siphonoglyphs, each attached to pair of directives. Retractor muscles diffuse; parietobasilar muscles not differentiated. Cnidom: Robust and gracile spirocysts, basitrichs, holotrichs, microbasic p-mastigophores (modified from Rodríguez et al. in review; changes in italics).

Type species. Alvinactis reu Rodríguez, Castorani and Daly, in review, by monotypy.

Alvinactis chessi n. sp.

Figs. 5-7, Table 2

Diagnosis. Column of preserved, contracted specimens smooth, delicate, more or less equal in diameter along length, diameter at base 19-35 mm, height 15-40 mm, with a distal belt of 24 perforate papillae. Column of living specimens trumpet-shaped, yellowish to white; tentacles moderately long, bluntly conical, without aboral thickenings. Tentacles with spirocysts, basitrichs, and holotrichs, the last only in the tips; holotrichs in column and pedal disc. Mesenteries hexamerously arranged, only first cycle perfect.

Etymology. Named after the Biogeography of Deep-Water Chemosynthetic

Ecosystems (ChEss) field project of the Census of Marine Life to honor the commitment 65 of this program to furthering systematic study of hydrothermal vent fauna.

Material examined. USNM #####: TowCam, dive J2-240, 26 September 2006, two specimens (holotype and paratype); USNM #####: Kilo Moana, dive J2-235 (black slurp), 16 September 2006, one specimen; USNM #####: Kilo Moana, dive J2-230

(black slurp), 06 September 2006, one specimen. Additional material. FMNH ####: Kilo

Moana, dive J2-137, 05 April 2005, one specimen; FMNH ####: TowCam, dive J2-139-

3-B1, 06 May 2005, one specimen.

Oral disc and tentacles. Oral disc slightly domed, with broad, tentacle-free space surrounding prominent mouth (Fig. 5B). In life, oral disc light brown, translucent, with faint dark lines marking mesenterial insertions; preserved specimen uniform opaque cream. Mouth elevated on conical hypostome, with large lips; mouth, lips, siphonoglyphs, and actinopharynx cream to white in life, same color as column and disc in preservation.

Up to 96 tentacles in four crowded marginal cycles, those of inner cycles longer than those of outer cycle (Figs. 5B,E,G). In preservation, tentacles blunt, longitudinally furrowed, with pore at tip, colored as column, length approximately equal to oral disc radius. In life, tentacles longer, more sharply tapering, those of inner cycle much longer than oral disc diameter (Figs. 5A,B,C). Some preserved specimens missing tentacles; point of attachment between margin and tentacle uniform rather than ragged, suggesting autotomy rather than damage (Fig. 5F). Longitudinal musculature of tentacles ectodermal

(Fig. 6D).

66

FIGURE 5. Alvinactis chessi n. sp. External anatomy: A, lateral view of living specimen;

B, oral view of living specimen; C, lateral view of living specimen; D, living specimen in being collected; E, lateral view of preserved specimen; F, detail of the distal perforated papillae (white arrows) and marginal ring (black arrow); G, detail of the marginal ring and cycles of tentacles; H, detail of a missing tentacle suggesting autotomy; I, detail of the distal perforated papillae (black arrow). Scale bars; A, B, C, D, 100 mm; E, 30 mm;

F, 5 mm; G, H, 2 mm; I, 3 mm. 67 Base and column. Column smooth, stout, cylindrical or top-shaped in preserved,

contracted specimens (Figs. 5E,F), height 15-38 mm, diameter at base 13-35 mm. In life,

column trumpet shaped, flaring slightly from base (Figs. 5A,C). Column thin-walled,

delicate, with 24 small but prominent mound-like papillae in endocoels between column

midline and region of marginal sphincter (Figs. 5F,I). Papillae solid, not adhesive or

histologically differentiated into verrucae, with central cinclide (Figs. 5F,I, 6F,G).

Column of living and preserved specimens cream; mesenterial insertions visible as

distinct opaque white lines. Mesenterial insertions furrow column of contracted

specimens. No fosse; sphincter forms marginal ring (Figs. 5A,F,G). Column musculature

strong, mesogleal, concentrated into a mesogleal marginal sphincter distally (Fig. 6B);

sphincter lies closer to gastrodermis than epidermis, does not taper (Fig. 6B).

Pedal disc adherent, muscular, same color as column, withdrawn inside column or

destroyed in all preserved specimens. Basilar muscles poorly developed (Fig. 6E).

FIGURE 6 (next page). Alvinactis chessi n. sp. Internal anatomy: A, cross section of the mesenteries at actinopharynx, showing diffuse retractor muscles; B, longitudinal section through distal column, showing mesogleal marginal sphincter and a perforated solid papilla (arrow); C, cross section of the mesenteries below actinopharynx, showing parietobasilar muscles (arrow); D, cross section through a tentacle showing longitudinal ectodermal muscles; E, cross section of the pedal disc showing basilar muscles; F, and G, longitudinal section through distal column showing a perforated papillae. Scale bars: A, 1 mm; B, 2 mm; C, D, E, 0.1 mm; F, G, 1 mm. 68

69 Mesenteries and internal anatomy. Mesenteries arranged hexamerously in four cycles, those of first cycle perfect; two pairs of directives, each attached to prominent siphonoglyph. Equal number of mesenteries distally and proximally. Mesenteries of first three cycles including directives fertile, with filaments; those of fourth cycle small, weak, lacking filaments and gametogenic tissue (Fig. 6A). All examined specimens sexually mature, with either female or male gametes in any single specimen; oocytes 0.02-0.15 mm in diameter.

Longitudinal muscles of mesenteries weak (Fig. 6A). Retractor muscles diffuse, span most of distance between body wall and filament, with many short, branched processes (Fig. 6A). Parietobasilar muscles not distinct from mesenterial lamella, with few short, broad processes and no pennon (Fig. 6C).

Cnidom. Robust and gracile spirocysts, basitrichs, holotrichs, microbasic p- mastigophores (Fig. 7). See Table 2 for size and distribution.

FIGURE 7 (next page). Alvinactis chessi n. sp. Cnidae: A, basitrich; B, holotrich; C, basitrich; D, microbasic p-mastigophore; E, holotrich; F, robust spirocyst; G, basitrich; H, holotrich; I, microbasic p-mastigophore; J, basitrich; K, microbasic p-mastigophore 1; L, microbasic p-mastigophore 2. 70

71 Table 2. Summary of size ranges of the cnidae of Alvinactis chessi n. sp. x¯ : mean length by mean width of capsules. SD: standard deviation. S: ratio of number of specimens in which each type was found to number of specimens examined. N: total number of capsules measured. F: frequency: +++ = very common, ++ = common, + = less common, --- = sporadic.

Category Range of length x¯ ± SD S N F A. reu (Rodríguez et B. kroghi and width of capsules al. in review) (Carlgren 1956) (!m) PEDAL DISC Basitrichs 24.2-41.7 x 2.6-4.9 33.9 ±3.9 x 3.5 ± 0.4 4/4 57 ++ 17.6-29.7 x 1.0-3.3 13.8-19.6 x 3.4-4.3(3) Holotrichs 22.1-33.2 x 4.1-5.52 27.0 ±3.3 x 4.4 ±0.5(*) 4/4 8 ---/÷ nd — (3) SCAPUS Basitrichs 20.4-42.2 x 2.6-4.6 31.9 ±5.0 x 3.5 ± 0.4 4/4 79 ++/+++ 19.2-29.5 x 1.5-3.2 Microbasic p-mastigophores(1) 24.3-39.4 x 4.3-6.1 30.2 ±3.1 x 5.2 ± 0.4 4/4 60 +++ 24.6-37.6 x 3.5-6.1 Present(3) Holotrichs(1) 22.6-36.7 x 3.9-7.9 26.9 ±3.3 x 5.2 ±0.7(*) 2/4 26 ÷/++ 18.6-25.4 x 3.0-3.7 TENTACLES Spirocysts 25.1-67.6 x 3.6-10.5 46.6 ±9.6 x 6.1 ± 1.6 5/5 46 ++ 16.1-59.5 x 2.2-7.8 41.3-65.7 x 3.6-5.5(3) Basitrichs 35.1-54.3 x 3.1-4.3 46.2 ±3.7 x 3.7 ± 0.2 5/5 60 +++ 13.9-38.6 x 1.3-3.4 15.5-22 x 3-3.5 Holotrichs(2) 42.5-55.9 x 4.5-7.9 49.4 ±3.2 x 6.1 ±0.7(*) 5/5 35 ++ 21.4-38.4 x 4.5-8.2 ACTINOPHARYNX Basitrichs 36.8-44.8 x 3.6-4.1 Contamination 1/3 4 ---/+ 17.2-37.2 x 1.1-3.4 28.2-33.8 x 3.5 Microbasic p-mastigophores 30.2-45.4 x 3.8-7.1 37.7 ±2.8 x 5.1 ± 0.8 3/3 60 +++ 27.3-39.4 x 3.5-5.8 28.2-39.5 x 4.2-5.6 FILAMENTS Basitrichs 15.2-27.1 x 2.0-3.4 19.7 ±5.0 x 2.7 ± 0.4 5/5 44 ++ 13.2-33.3 x 1.2-4.1 15.5 x 2.8 (rare) Microbasic p-mastigophores 1 20.0-30.5 x 3.2-4.7 26.5 ±2.9 x 4.1 ±0.5(*) 4/5 17 +/++ nd nd Microbasic p-mastigophores 2 32.8-46.0 x 3.7-5.9 38.9 ±2.7 x 4.7 ± 0.4 5/5 46 +/+++ 28.0-39.4 x 3.0-5.8 28.2-38 x 5.6-6.3

(*) Average based measurements of fewer than 40 capsules; the measurement of at least 40 capsules is usually considered minimum for statistical significance (Williams 1998; 2000). (1) Restricted to the margin in A. reu. (2) Present only in the tips of tentacles. (3) Data from the present study (ZMUC type material collection). 72 Taxonomic remarks. Alvinactis chessi n. sp. is the second species attributed to this genus, which is comprised only of species living in chemosynthetically active deep- sea habitats. As is true of most other actiniarians from chemosynthetic environments, A. chessi n. sp. presents a combination of characters incompatible with the diagnosis of any described genus. In A. chessi n. sp. the distal row of cinclides is associated with solid papillae, whereas in A. reu, the cinclides are associated with verrucae (Rodríguez et al. in review). Alvinactis chessi n. sp. also resembles the actinostolid deep-sea genus

Bathydactylus Calgren, 1928. Although Bathydactylus includes two species, the type species B. valdiviae Carlgren, 1928 is known from only a single, poorly preserved specimen (Rodríguez et al. in review). The second species of the genus, B. krogni

Carlgren, 1956, has a conspicuous distal row of papillae that resembles those of A. chessi n. sp.; however, after the re-examination of the type material of B. krogni, we find no evidence that its papillae are perforated.

The cnidom of Alvinactis chessi n. sp. more closely resembles that of A. reu than

B. krogni (see Table 2). As is true of A. reu, the tentacles of A. chessi n. sp. have holotrichs and both robust and gracile spirocysts (Fig. 7); in contrast, in B. krogni, the tentacles have only gracile spirocysts and lack holotrichs. Because the only anatomical difference between A. reu and A. chessi n. sp. is the nature of the structures on which the cinclides are mounted and not the presence or absence of the cinclides, we assign this new species to Alvinactis rather than to Bathydactylus.

In addition to differences in the structure of the column protrusions, A. chessi n. sp. and A. reu differ in the size and distribution of cnidae (see Table 2). Alvinactis chessi n. sp. has longer holotrichs in the tentacles and column than A. reu. Microbasic p- 73 mastigophores and holotrichs are restricted to the column margin in A. reu but not in A. chessi n. sp., however, holotrichs are not very abundant in the column of either species.

Alvinactis chessi n. sp. has holotrichs in the pedal disc but they are absent in A. reu.

Because they are rare and not found in all specimens, the few basitrichs in the actinopharynx of A. chessi n. sp. may be contaminants from the tentacles, whereas this type is invariably present (in low abundance) in the actinopharynx of A. reu.

Furthermore, the species of Alvinactis differ in geographic distribution: A. reu has been reported from a hydrothermal site in the northeastern Pacific (Rodriguez et al. in review) whereas A. chessi n. sp. is from the southwestern Pacific.

Family Hormathiidae Carlgren, 1932

Genus Chondrophellia Carlgren, 1925

Definition. Hormathiidae with well developed base. Body elongated, without cinclides, divisible into scapus and scapulus; scapus with cuticle and tubercles distally, typically12 short rows of conspicuous tubercles. Scapulus longitudinally sulcated.

Marginal sphincter very strong, mesogleal. Tentacles hexamerously arranged, almost as numerous as mesenteries at base. Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal. Six pairs of perfect mesenteries. Mesenteries of oldest cycles, including directives, fertile, with filaments and acontia. Mesenteries of youngest full cycle and of subsequent partial cycles only present proximally, sterile, without filaments or acontia. Same number or fewer mesenteries at column midline than distally or proximally. Below actinopharynx, inner part of non-directive mesenteries may curve 74 towards exocoels. Perfect and stronger imperfect mesenteries with diffuse retractor muscles; retractor muscles usually situated fairly close to body wall. Parietobasilar muscles weak. Acontia well developed. Cnidom: spirocysts, basitrichs and microbasic p- mastigophores (modified from Carlgren (1949); changes in italics).

Type species. Actinauge nodosa var. coronata Verrill, 1883, by subsequent designation (Carlgren 1949; Fautin et al. 2007)

Remarks. Carlgren (1949) stipulates that the interior (filament edge) of the larger non-directive mesenteries curve away from their paired member, splaying towards the exocoels. This is not the case for all mesenteries of all specimens we have examined, and may be an artifact of contraction rather than an intrinsic feature. Thus, we have inserted

“may” in the account of this feature in the definition of Chondrophellia.

Chondrophellia orangina n. sp.

Figs. 8-10, Table 3

Diagnosis. In life, column stout, trumpet-shaped, pale orange to white, covered with blackish cuticle, with relatively short, tapering, uniformly orange marginal tentacles

(Figs. 8A,D). Oral disc slightly concave in life, orange to pink. Mesenteries hexamerously arranged in five cycles, fifth cycle present at limbus only; although all larger mesenteries fertile, only those of first cycle perfect.

Etymology. Species epithet refers to the vivid orange color of living specimens.

Material examined. USNM #####: Kilo Moana, dive J2-235 (black slurp), 16

September 2006, two specimens; USNM #####: TowCam, dive J2-233 (yellow slurp), 13 75 September 2006, one specimen. Additional material. FMNH ####: Kilo Moana, dive J2-

137-4B1, 03 May 2005, two specimens.

Oral disc and tentacles. Oral disc flat, with broad, tentacle-free space surrounding prominent, slit-like mouth with two prominent siphonoglyphs. Oral disc orange to pink with white margin in life, pale orange to pink in preserved specimens.

Siphonoglyphs and actinopharynx of preserved specimens light brown, orange in living specimens. Musculature of oral disc strong, ectodermal.

FIGURE 8. Chondrophellia orangina n. sp. External anatomy: A, expanded living specimen; B, lateral view of preserved specimen; C, oral view of preserved specimen, showing notice the scapulus (arrows); D, expanded living specimen. Scale bars: A, D,

100 mm; B, 20 mm; C, 20 mm.

76 Approximately 100 tentacles in six crowded marginal cycles, inner and outer cycles approximately equal in length. Tentacles typically inside column in contracted specimens; distal column covers oral disc and base of tentacles in all specimens examined (Figs. 8B,C). In contraction, tentacles blunt, longitudinally furrowed, about 15 mm long, slightly longer than oral disc radius; in life, tentacles longer, more sharply tapering, those of inner cycle slightly longer than those of outer cycle (Figs. 8A,D).

Tentacles of inner cycles of tentacles typically held erect, those of outermost cycle held out or pointing towards substrate (Figs. 8A,D). In life, tentacles colored as oral disc, with white markings on aboral base (Figs. 8A,D). Tentacles of preserved specimens orange to pink, paler at tips. Ectodermal longitudinal muscles of tentacles equally developed on oral and aboral sides.

FIGURE 9 (next page). Chondrophellia orangina n. sp. Internal anatomy: A, cross section of the mesenteries below actinopharynx, showing diffuse retractor muscles and abundant ova; B, cross section of the mesenteries below actinopharynx, showing parietobasilar muscles; C, longitudinal section through distal column, showing mesogleal marginal sphincter (arrows); D, detail of the marginal sphincter muscles fibers embedded in the mesoglea; E, cross section through a tentacle showing longitudinal ectodermal muscles; F, cross section of the pedal disc showing basilar muscles (arrows). Scale bars:

A, 1 mm; B, 0.2 mm; C, 4 mm; D, E, 0.1 mm; F, 0.2 mm. 77

78

Base and column. Column of preserved, contracted specimens stout, cylindrical; diameter at base 31-51 mm, height 25-45 mm. In life, column cylindrical, flaring abruptly at oral disc (Figs. 8A,D). Column of living specimens white underneath dark cuticle.

Column differentiated into cuticle-free distal scapulus and thick-walled, cuticulate proximal scapus (Fig. 8C) that bears large, regularly arranged tubercles forming ridges distally (Fig. 8B). Mesenterial insertions more prominent distally because of ridges and tubercles. Column musculature concentrated into a strong mesogleal marginal sphincter distally; sphincter centered in mesoglea, larger distally, tapering proximally (Fig. 9C).

Pedal disc adherent, muscular, flat, same color as column, may retain thin covering of small particles from substrate. Basilar muscles poorly developed (Fig. 9F).

Mesenteries and internal anatomy. Mesenteries arranged hexamerously in five regular cycles; fifth cycle present at limbus only. Two pairs of directives, each attached to a prominent siphonoglyph. Only mesenteries of first cycle perfect. Mesenteries of first three cycles fertile; mesenteries of fourth and fifth cycle sterile and without filaments

(Fig. 9A). All specimens collected in September sexually mature, with either female or male gametes in any single specimen (Fig. 9A). Oocytes small given size of animal, 0.04-

0.16 mm in diameter. Acontia abundant, tightly coiled, present on all fertile mesenteries.

Longitudinal muscles of mesenteries strong (Fig. 9A). Retractor muscles strong, diffuse, span half of the distance between body wall and filament, becoming restricted closer to body wall (Fig. 9A). Parietobasilar muscles weak, not well differentiated from mesenterial lamella, lacking distinct pennon (Fig. 9B). 79 Cnidom. Robust and gracile spirocysts, basitrichs, microbasic p-mastigophores

(Fig. 10). See Table 3 for size and distribution.

Taxonomic remarks. Chondrophellia contains three valid species: C. africana

Carlgren, 1928, C. coronata (Verrill, 1883), and C. orangina n. sp. Chondrophellia orangina n. sp. is the most distinctive, having more cycles of mesenteries than either C. coronata or C. orangina n. sp. The two previously described species are extremely similar, differing only in the thickness of the cuticle (thinner in C. africana), the shape of the tubercles (flatter in C. africana), and the morphology of the retractor muscles

(stronger and more restricted in C. africana). In C. orangina n. sp., the fourth cycle of mesenteries is present throughout the body and the fifth cycle is only present proximally; in C. coronata and C. africana, the third cycle is present throughout the body and the fourth cycle is only present proximally. The last full cycle of mesenteries is sterile in all species of Chondrophellia; this is the fourth cycle in C. orangina n. sp. and the third cycle in C. africana and C. coronata. Furthermore, C. orangina n. sp. differs from both previously described species of Chondrophellia in having microbasic p-mastigophores in the filaments, although the cnidom is imperfectly known in C. africana and C. coronata.

FIGURE 10 (next page). Chondrophellia orangina n. sp. Cnidae: A, basitrich 1; B, basitrich 2; C, microbasic p-mastigophore; D, basitrich 1; E, basitrich 2; F, microbasic p- mastigophore; G, basitrich 1; H, basitrich 2; I, microbasic p-mastigophore; J, robust spirocyst; K, basitrich 1; L, basitrich 2; M, basitrich 1; N, basitrich 2; O, microbasic p- mastigophore; P, basitrich 1; Q, microbasic p-mastigophore; R, basitrich 1; S, basitrich 2. 80 81 Table 3. Summary of size ranges of the cnidae of Chondrophellia orangina n. sp. x¯ : mean length by mean width of capsules. SD: standard deviation. S: ratio of number of specimens in which each type was found to number of specimens examined. N: total number of capsules measured. F: frequency: +++ = very common, ++ = common, + = less common, --- = sporadic. nd: no data.

Range of length x¯ ± SD C. africana C. coronata Category and width of capsules S N F (Carlgren 1928) (Carlgren 1942) (!m) PEDAL DISC Basitrichs 1 10.0-14.4 x 1.3-2.9 11.8 ±0.9 x 2.0 ± 0.4 3/3 42 ++ nd nd Basitrichs 2 15.1-18.9 x 1.6-2.4 Contamination? 1/3 14 nd nd Microbasic p-mastigophores 29.4-38.3 x 3.8-4.8 Contamination? 1/3 10 nd nd SCAPUS Basitrichs 1 10.1-14.3 x 1.7-2.8 11.5 ±1.1 x 2.3 ± 0.2 3/3 46 ++ nd nd Basitrichs 2 17.1-20.6 x 2.8-3.4 18.5 ±1.0 x 3.1 ±0.2(*) 2/3 8 ---/+ nd nd Microbasic p-mastigophores 28.8-36.7 x 3.8-4.9 32.3 ±2.1 x 4.2 ±0.3(*) 2/3 23 +/+++ nd nd SCAPULUS Basitrichs 1 10.7-15.7 x 1.7-2.8 12.9 ±1.4 x 2.2 ±0.4(*) 2/2 16 + nd nd Basitrichs 2 19.7-32.8 x 2.5-4.0 25.8 ±2.5 x 3.2 ± 0.3 2/2 40 ++/+++ nd 18-23 x 2.8 Microbasic p-mastigophores 25.8-31.1 x 3.0-4.5 29.6 ±2.1 x 4.0 ±0.6(*) 2/2 5 --- nd nd TENTACLES Spirocysts 27.2-67.6 x 3.4-13.1 47.2 ±10.0 x 6.6 ± 2.5 3/3 67 ++ 19-43 x 2-7 19-50 x 2-7.5 Basitrichs 1 13.7-19.7 x 1.9-3.3 16.8 ±2.1 x 2.6 ±0.4(*) 2/3 13 + 19-24 x 2.5 22-32 x 2.8 Basitrichs 2 31.3-50.4 x 2.7-4.0 41.9 ±5.1 x 3.4 ± 0.3 2/3 40 ++ nd nd ACTINOPHARYNX Basitrichs 1 15.5-23.0 x 1.4-2.8 18.5 ±1.5 x 2.3 ±0.4(*) 2/3 31 +/++ 24-29 x 2.5 22-34 x 2.8-3.5 Basitrichs 2 31.3-47.5 x 2.8-4.1 39.1 ±3.2 x 3.4 ± 0.3 3/3 55 +/++ --- — Microbasic p-mastigophores 27.3-35.5 x 3.9-5.8 31.4 ±2.0 x 4.6 ± 0.5 3/3 61 ++/+++ 22-24 x 3.5 25.5-28.5 x 4.2 FILAMENTS Basitrichs 10.2-18.4 x 1.8-2.7 16.6 ±2.8 x 2.3 ± 0.4 3/3 40 ---/++ nd 15.5-17.5 x 2-2.5 Microbasic p-mastigophores 29.2-37.8 x 3.4-5.7 31.8 ±2.1 x 4.5 ± 0.6 3/3 60 +++ nd nd ACONTIA Basitrichs 1 15.2-25.0 x 2.0-2.8 19.8 ±2.8 x 2.4 ±0.3(*) 2/3 37 ++ nd nd Basitrichs 2 44.0-58.8 x 3.1-5.0 49.6 ±3.4 x 3.9 ± 0.4 3/3 60 +++ 38-46 x 2.5-3 30-53 x 2.8-4.2

(*) Average based measurements of fewer than 40 capsules; the measurement of at least 40 capsules is usually considered minimum for statistical significance (Williams 1998; 2000). 82 Family Sagartiidae Gosse, 1858

Genus Sagartiogeton Carlgren, 1924

Definition. Sagartiidae with well developed base. Body may be divisible into scapus and scapulus. Scapus often but not necessarily with a cuticle or tenaculi. Column often with cinclides in its upper part, usually near limbus. Margin distinct or tentaculate.

Well-developed mesogleal marginal sphincter. Tentacles usually long, conical, hexamerously, octamerously, decamerously or irregularly arranged, as a rule not thickened on their aboral sides. Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal. Siphonglyphs usually two, sometimes one or three; one to three pairs of directives. At least six pairs of perfect mesenteries, usually more. All stronger mesenteries fertile. Younger mesenteries grow from both limbus and margin, typically originating earlier at margin than at limbus. In the region of the actinopharynx, perfect and stronger imperfect mesenteries bear fairly restricted retractor muscles; retractors often reniform, rarely circumscribed. Parietobasilar muscles weak. Cnidom: spirocysts, basitrichs, microbasic p-mastigophores and microbasic amastigophores (modified from

Carlgren (1949); changes in italics).

Type species. Sagartiogeton robustus Carlgren, 1924, by subsequent designation

(Carlgren 1949; Fautin et al. 2007).

Remarks. Since Kadosactis Danielssen, 1890 is now in its own family (Riemann-

Zürneck 1991), and is clearly distinguished from Sagatiogenton by several features,

Carlgren’s (1949) distinction between the tenaculi of Sagartiogeton and Kadosactis is now irrelevant to the definition of the Sagartiogeton, and thus we have deleted it. In 83 addition, we broadened the definition of Sagartiogeton to include the possibility of slight thickening in the mesoglea of the aboral base of the tentacles because this feature is seen in S. erythraios n. sp.

Sagartiogeton erythraios n. sp.

Figs. 11-13, Tables 4-5

Diagnosis. In life, column short, rosy pink to white, with deep red to pink, tapering tentacles that are lighter at the tips (Fig. 11A). Tentacles with microbasic p- mastigophores, basitrichs, and spirocysts; microbasic p-mastigophores not in distinct batteries. Mesenteries in three hexamerous cycles; those of first two cycles perfect.

Etymology. Species epithet from the Greek, meaning blood red, in reference to the color of the living animal.

Material examined. USNM #####: ABE, dive J2-237, 23 September 2006, two specimens (holotype and paratype); USNM #####: Kilo Moana, dive J2-235 (black slurp), 16 September 2006, one specimen.

Oral disc and tentacles. Oral disc flat, with broad, tentacle-free space surrounding prominent mouth. Musculature of oral disc strong, ectodermal. Oral disc margin white. Lips and oral disc of preserved specimens deeper red or pink than column but not as deeply colored as tentacles or actinopharynx; siphonoglyphs and actinopharynx of preserved specimens blood red.

Approximately 48 tentacles in four crowded marginal cycles. Tentacles typically retracted inside column in contraction; distal column covers oral disc and base of 84 tentacles in all specimens examined (Figs. 11B,C). In contraction, tentacles blunt, longitudinally furrowed, slightly longer than oral disc radius, all approximately 6 mm long; color in preservation beige to pink. In life, tentacles long, sharply tapering, those of inner cycle approximately equal in length to the oral disc diameter, deep pink or red at base, becoming white at tips. Tentacles of inner cycles typically held erect, those of outermost cycle held out or pointing towards substrate (Fig. 11A). Tentacles of preserved specimens red to brown, parts of tentacles inside contracted specimens more deeply colored than those exposed. Ectodermal longitudinal muscles of tentacles slightly more developed on oral side of tentacles; endodermal circular muscle evenly developed.

FIGURE 11. Sagartiogeton erythraios n. sp. External anatomy: A, expanded living specimen; B, lateral view of contracted, and preserved specimen; C, lateral-oral view of preserved specimen, notice showing the acontia (arrow); D, detail of a cuticulate tenaculum on the scapus, notice stratified cuticle. Scale bars: A, 50 mm; B, 10 mm; C, 10 mm; D, 0.05 mm.

85 Base and column. Column of preserved, contracted specimens stout, dome- shaped, diameter at base 13-27 mm, height 13-18 mm. Column differentiated into thin walled distal scapulus and thick walled proximal scapus; scapus bears cuticle and small, irregularly spaced papillae (Figs. 11B,C,D). Papillae solid, with tightly adhering cuticle

(Fig. 11D). No cinclides. Mesenterial insertions not distinct in contracted preserved specimens. Preserved specimens brownish cream. In life, column cylindrical, color of scapus obscured by brownish cuticle, scapulus pale pink. Because scapulus lacks cuticle, contracted living specimens have pale ring at margin (Fig. 11A). Column musculature concentrated into a strong mesogloeal marginal sphincter distally; sphincter long, encompassing entire length of scapulus, stronger distally, closer to gastrodermis than epidermis (Fig. 12A).

Pedal disc adherent, muscular, flat, same color as column, retains thin covering of small particles from substrate. Basilar muscles well developed (Fig. 12D).

FIGURE 12 (next page). Sagartiogeton erythraios n. sp. Internal anatomy: A, longitudinal section through distal column, showing mesogleal marginal sphincter; B, cross section of the directive mesenteries attached to the siphonoglyph (arrow), showing diffuse retractor muscles; C, cross section through a tentacle showing longitudinal ectodermal muscles; D, cross section of the pedal disc showing basilar muscles; E, cross section of the mesenteries proximally, showing differentiated parietobasilar muscles differentiated (arrow). Scale bars: A, B, 1 mm; C, D, 0.1 mm; E, 1 mm. 86

87 Mesenteries and internal anatomy. Mesenteries hexamerously arranged in three cycles; equal numbers of mesenteries distally and proximally but sometimes fewer in the middle. Two pairs of directives, each attached to prominent siphonoglyph. All mesenteries of first cycle perfect; some mesenteries of second cycle perfect; no mesenteries of third cycle perfect. All larger mesenteries, including directives fertile and with acontia (Figs. 12B,E). All specimens collected in late September sexually mature, with either female or male gametes in any single specimen; oocytes 0.04-0.12 mm in diameter (Figs. 12B,E).

Longitudinal muscles of mesenteries strong (Figs. 12B,E). Retractor muscles of all mesenteries diffuse but restricted, spanning more than half of distance between body wall and filament (Figs. 12B,E). Parietobasilar muscles weak, not differentiated in stronger mesenteries, with globular mesogleal pennons adjacent to retractor muscle in some imperfect mesenteries (Figs. 12B,E).

Cnidom. Robust and gracile spirocysts, basitrichs, microbasic p-mastigophores

(Fig. 13). See Table 4 for size and distribution.

FIGURE 13 (next page). Sagartiogeton erythraios n. sp. Cnidae: A, basitrich; B, basitrich 1; C, basitrich 1; D, microbasic p-mastigophore; E, gracile spirocyst; F, robust spirocyst; G, basitrich 1; H, basitrich 2; I, microbasic p-mastigophore; J, basitrich 1; K, microbasic p-mastigophore; L, basitrich 1; M, microbasic p-mastigophore 1; N, microbasic p-mastigophore 2; O, basitrich 1; P, basitrich 2; Q, microbasic p- mastigophore. Scale bar: Q, 50 µm. 88

89 Table 3. Summary of size ranges of the cnidae of Chondrophellia orangina n. sp. x¯ : mean length by mean width of capsules. SD: standard deviation. S: ratio of number of specimens in which each type was found to number of specimens examined. N: total number of capsules measured. F: frequency: +++ = very common, ++ = common, + = less common, --- = sporadic. nd: no data.

Range of length S. abyssorum S. ingolfi S. verrilli S. flexibilis Category and width of capsules x¯ ± SD S N F (Carlgren 1942) (Carlgren 1942) (Carlgren 1942) (Carlgren, 1942) (!m) PEDAL DISC Basitrichs 13.1-20.0 x 2.1-2.9 17.2±1.4 x 2.5±0.2* 1/1 20 ++ nd nd nd nd SCAPUS Basitrichs 10.5-19.0 x 1.7-3.8 15.7±2.6 x 2.8±0.4 3/3 44 ++ 19.7-26.8 x 2.8 9-12.7 x 1.5 13.5-22 x 2.8 nd M. p-mastigophores 42.5-48.6 x 6.4-8.9 Contamination 1/3 6 + 30-36 x 5 14-19.7 x 3-5 24-35 x 4-4.5 12.7-15.5 x 2.8- 3.5 SCAPULUS Basitrichs 11.0-21.6 x 2.5-3.8 16.6±2.9 x 3.1±0.3* 2/2 24 +/++ nd nd nd nd M. p-mastigophores 37.3-56.6 x 5.4-9.1 45.1±3.7 x 6.8±0.8 2/2 40 ++ nd nd nd nd TENTACLES Gracile spirocysts 25.6-60.1 x 2.8-7.1 37.7 ±7.4 x 5.0±0.9 3/3 42 ++ 46 x 5 43 x 5-5.5 17-35 x 1.5-5 27 x 4.5 Robust spirocysts 29.1-70.1 x 4.7-12.1 53.5 ±8.2 x 7.8±2.0* 3/3 39 ++ nd nd nd nd Basitrichs 1 10.2-22.6 x 1.8-3.0 15.5 ±3.3 x 2.3±0.3* 3/3 31 +/++ nd nd nd nd Basitrichs 2 24.0-36.8 x 2.1-3.7 28.2±2.5 x 2.9 ±0.3* 3/3 35 +/++ 22-26 x 2.8 22-24 x 2.5 21-29 x 2.5-2.8 17-24 x 2.8 M. p-mastigophores 47.3-69.7 x 5.0-11.4 54.0±4.3 x 6.8±1.5* 3/3 27 + 41-50 x 5.5 26.8-35.2 x 4.2-5 24-35 x 3.5-4.2 26-29 x 3.5-4 ACTINOPHARYNX Basitrichs 1 13.6-19.1 x 2.2-3.1 15.9±1.4 x 2.7±0.2* 3/3 34 +/++ nd 13-17 x 2-2.5 nd nd Basitrichs 2 39.2-45.8 x 2.9-4.0 Contamination 1/3 6 --- 31-38 x 3.5 24-38 x 3-3.5 23.5-31 x 2.8-3 26-27 x 2.5-2.8 M. p-mastigophores 55.7-67.6 x 5.2-11.6 61.8±2.4 x 6.7±1.4* 3/3 32 ++/+++ 35-41 x 5.5 31-36.7 x 4.5-5.2 nd 26.8-28.2 x 3.5-4 M. p-mastigophores — nd 25.4-28 x 4.5-5 28-31 x 4.2 nd FILAMENTS Basitrichs 11.8-17.7 x 2.0-3.2 14.1±1.5 x 2.7±0.3 3/3 49 +/++ 11.3-15.5 x 1.5-2 29.6-33.8 x 3 25.5 x 2.8 nd M. p-mastigophores 1 30.3-43.3 x 3.5-7.4 35.4±3.1 x 4.4±0.7 3/3 63 ++ 28.2-41 x 4.2-5 29-36.7 x 4.2 25-34 x 4-4.5 nd M. p-mastigophores 2 44.4-63.0 x 4.4-7.5 51.0±3.5 x 5.4±0.7 3/3 40 +/++ nd 21.5-25.4 x 4.2 11.5-12 x 3.5 nd other 16.2 x 3 ACONTIA Basitrichs 1 10.2-17.9 x 1.8-3.1 13.9±1.0 x 2.7 ±0.2* 2/3 21 +/++ 15.5-19.7 x 2 nd nd nd Basitrichs 2 49.1-63.5 x 3.8-5.5 58.8 ±3.6 x 4.6± 0.4 3/3 41 ++/+++ 34-55 x 3-3.5 48-62 x 3.5-4.2 38-38 x 2.8 34-41 x 2.8-3.5 M. p-mastigophores 86.6-127.0 x 5.5-13.8 98.2 ±11.3 x 8.5±1.6 3/3 49 +++ 72-86 x 6.5-7 60-88.8 x 7-7.5 58-67 x 5.6-6.3 53-66 x 5.6-7

(*) Average based measurements of fewer than 40 capsules; the measurement of at least 40 capsules is usually considered minimum for statistical significance (Williams 1998; 2000). 90 Taxonomic remarks. Sagartiogeton erythraios n. sp. is distinguished from other members of the genus based on attributes of the column, mesenteries, and musculature

(Table 5). This species has slight thickenings of the aboral base of the tentacles and extremely large p-mastigophores in the acontia, attributes that suggest an affiliation with

Kadosactis. In S. erythraios n. sp., the tentacles are only slightly thickened at the base, with less difference between the oral and aboral sides than in Kadosactis. However, none of the specimens we examined had cinclides, precluding placement in Kadosactis. Thus, we place this species in Sagartiogeton because Kadosactis is extremely homogeneous

(Riemann-Zürneck 1991; Rodríguez and López-González 2005), whereas Sagartiogeton is more variable, and can thus more readily accommodate the suite of features seen in S. erythraios n. sp. Furthermore, the differences between this species and other members of

Sagartiogeton seem to be differences in degree rather than kind (Table 5). 91 Table 5. Comparison between Sagartiogeton erythraios n. sp., other species of Sagartiogeton from the deep-sea, and Kadosactis antarctica (Carlgren, 1928) from the Southern Hemisphere. Data from original descriptions, Carlgren (1942), and Rodríguez and López-González (2005). Species # pairs perfect # tentacles Retractor muscles Cinclides Column mesenteries Kadosactis 12 48 Diffuse Distal row of 22 cinclides in the With remains of cuticle antarctica endocoels between scapus and and small mesogleal (Carlgren, 1928) scapulus papillae in the scapus S. erythraios 12 48 Diffuse, may be None With cuticle and n. sp. restricted on parietal side numerous scattered tenaculi S. verrilli Carlgren, 12 96 Restricted to middle Cinclides at limbus and below Densely scattered 1942 region of mesenteries sphincter tenaculi S. ingolfi Carlgren, 10 80 Restricted and Cinclides in proximal part and Weak cuticle, scattered 1928 circumscribed below sphincter tenaculi S. flexibilis 6 36 Strong and “somewhat On scapulus With tenaculi and well (Danielssen, 1890) circumscribed” in perfect developed cuticle mesenteries S. abyssorum 12 90-100 Diffuse but strongly Probably without Not cuticle, column Carlgren, 1942 restricted smooth

92 Other Hexacorallia

These collections contained a few actiniarians for which the genus and species could not be determined and many specimens of an unidentified zoanthidean (Anthozoa:

Hexacorallia: Zoanthidea).

The most conspicuous of the unidentifiable actiniarians are small (column diameter 5-30 mm) uniformly bright yellow animals collected at TowCam during dive

J2-240 (Figs. 14E,F,G). The acontia of these specimens contain only basitrichs, and the mesenteries are not divisible into macro- and micro-cnemes; thus, these animals belong to Hormathiidae. The column bears solid mesogleal papillae arranged in longitudinal rows, a cinclide is associated with each directive endocoel, and the aboral base of each tentacle is slightly thickened. These features, and the general shape and aspect of the column, suggest that these specimens belong to Amphianthus Hertwig, 1882.

Very little is known about most nominal species in Amphianthus (Riemann-

Zürneck 1987). The details of anatomy in the ELSC specimens are consistent with those of A. bathybium Hertwig, 1882, but the types and size ranges of cnidae differ slightly

(compare Table 6 to Riemann-Zürneck 1987). Amphianthus bathybium has a very broad reported range, extending from the eastern North Atlantic to Japan (Fautin 2007), and encompassing the Lau Basin. However, many of the species of Amphianthus are of uncertain taxonomic status (Riemann-Zürneck 1987), and so it is possible that some specimens reported as A. bathybium represent other species. A detailed revision of all nominal species of Amphianthus is required to evaluate the status of A. bathybium and identify taxonomically useful features for the genus. Pending such a revision, we prefer 93 not to associate these specimens with an existing species, and cannot justify erecting a new one.

FIGURE 14. Other Hexacorallia. A, Actinostolidae sp., preserved and contracted specimen; B, Actinostolidae sp. in situ on sulfide; C, Zoanthidea sp., preserved specimens on basalt; D, Zoanthidea sp. in situ on basalt; E, Amphianthus sp. preserved and contracted specimens, notice including the small specimens generated clonally through pedal laceration; F, Amphianthus sp. in situ on basalt; G, contracted specimens of

Amphianthus sp. on basalt in situ. Scale bars: A-G, 10 mm.

94 Several specimens of a relatively large (column diameter 30-32 mm), cuticle- bearing sea anemone were collected on dive J2-152 on 30 May 2005 (Figs. 14A,B).

These specimens have a strong mesogleal marginal sphincter and have mesenteries arranged according to the “Actinostola rule” (Carlgren 1949), and thus we refer them to

Actinostolidae. Most of these specimens have prominent, cuticle-covered papillae on the column, but the size and arrangement of these papillae is not uniform across specimens.

In general external appearance, these specimens resemble Seepactis galkini Sanamyan and Sanamyan, 2007 and Hadalanthus knudseni Carlgren, 1956, but they do not match the type specimens of either species. Specimens of very similar external morphology collected at a single site vary in the occurrence of acontia and in the adherence to the

“Actinostola rule”; whether this represents a single, highly polymorphic species or multiple species is not clear given the present material.

The most abundant anthozoans at the ELSC are small (column height to 50 mm, diameter to 3 mm), sediment-encrusted, tubular polyps belonging to the order Zoanthidea

(Figs. 14C,D). All specimens occur on bare basalt substrate and, although most are solitary, some polyps are connected via thin stolons. These zoanthideans are unlike any described species in terms of anatomy or cnidom. However, their geographic range and habitat is similar to that reported for Abyssoanthus nankaiensis Reimer, Sinniger,

Fujiwara, Hirano and Maruyama, 2007. Abyssoanthus nankaiensis was described based on DNA sequences and its anatomy is unknown. 95 Table 6. Summary of size ranges of the cnidae of Amphianthus sp. x¯ : mean length by mean width of capsules. SD: standard deviation. S: ratio of number of specimens in which each type was found to number of specimens examined. N: total number of capsules measured. F: frequency: +++ = very common, ++ = common, + = less common, --- = sporadic. nd = no data.

Range of length x¯ ± SD A. bathybium (Riemann- Category and width of capsules S N F Zürneck 1987) (!m) PEDAL DISC Basitrichs 11.1-15.9 x 2.2-2.9 13.2 ±1.3 x 2.6 ± 0.2 3/3 17 ---/+ nd Microbasic p-mastigophores 14.8-21.5 x 3.8-5.4 18.3 ±1.3 x 4.4 ± 0.3 3/3 40 ++/+++ nd SCAPUS Basitrichs 1 9.7-14.2 x 2.1-3.1 12.9 ±1.4 x 2.5 ± 0.3* 3/3 9 ---/+ nd Basitrichs 2 15.4-22.3 x 3.3-5.1 19.0 ±1.5 x 4.3 ± 0.5* 3/3 37 +/++ 23.5-25 x 3-3.5 Microbasic p-mastigophores — 21-23 x 3.5-4 Holotrichs 17.1-27.1 x 4.4-9.4 21.2 ±2.1 x 7.1 ± 1.2 3/3 40 ++ nd TENTACLES Robust spirocysts 21.1-53.9 x 3.4-14.3 34.1 ±6.5 x 6.6 ± 2.3 3/3 60 +++ 70 x 7-9 Basitrichs 16.5-25.0 x 3.7-4.6 20.5 ±2.2 x 4.2 ± 0.3* 3/3 10 ---/+ 22-28 x 3.5 Holotrichs 1 19.4-25.4 x 5.0-8.0 22.4 ±1.7 x 6.5 ± 0.8* 1/3 17 ---/+ 29.5-34 x 5-7 Holotrichs 2 30.6-41.3 x 5.5-7.7 33.8 ±5.0 x 6.5 ± 0.9* 2/3 4 --- 35-41 x 3.5-4 ACTINOPHARYNX Basitrichs 16.4-37.2 x 3.0-4.9 31.2 ±3.8 x 4.0 ± 0.4 3/3 42 ++/+++ 27-28.5 x 3 Microbasic p-mastigophores 23.1-29.5 x 3.4-5.5 26.1 ±1.5 x 4.6 ± 0.5(1) 3/3 29 ++ 23.5-28 x 3.5 Holotrichs 18.8-28.1 x 3.7-5.9 23.5 ±3.8 x 4.8 ± 0.9* 3/3 9 ---/+ nd FILAMENTS Basitrichs 10.0-15.6 x 1.6-2.9 12.6 ±1.7 x 2.6 ±0.3* 3/3 14 ---/+ 13-16 x 2 Microbasic p-mastigophores 19.6-29.6 x 3.5-5.4 25.3 ±2.0 x 4.4 ± 0.5 3/3 60 ++/+++ 23.5-28 x 3.5 Holotrichs 29.0-41.8 x 4.2-6.7 35.8 ±3.9 x 5.3 ± 0.5 2/3 26 + nd ACONTIA Basitrichs 1 11.9-16.7 x 2.2-3.2 13.6 ±1.4 x 2.6 ± 0.3* 3/3 21 +/++ 14.5-19 x 2 Basitrichs 2 35.6-48.2 x 4.1-5.4 42.9 ±3.1 x 4.8 ± 0.4 3/3 52 +++ 41-48 x 3.5-4

(*) Average based measurements of fewer than 40 capsules; the measurement of at least 40 capsules is usually considered minimum for statistical significance (Williams 1998; 2000). (1) Abundant broken capsules. 96 Ecological Observations

The vent communities of the western Pacific back-arc basins are taxonomically similar at the levels of species and genera across the biogeographic province

(Desbruyères et al. 1994; 2006a; Tunnicliffe and Fowler 1996). All sea anemones reported from chemosynthetic environments (Table 7) belong to one of five families:

Actinostolidae, Actinoscyphiidae, Hormathiidae, Kadosactidae, and Sagartiidae (Daly and Gusmão 2007; Sanamyan and Sanamyan 2007; Rodríguez et al. in review).

Boloceroides daphneae Daly, 2006 (Boloceroididae), is reported from near hydrothermal vents at East Pacific Rise (EPR) (Desbruyères et al. 2006b), but Daly (2006) notes that this species inhabits cliff faces and rocky outcrops 100 m or more from hydrothermal vents and is commonly found in the general deep-sea.

Sixty-four percent of the sea anemones reported from chemosynthetic environments are known only from those habitats, and only four genera are widespread (Table 7).

Marianactis bythios Fautin and Hessler, 1989, was described from hydrothermal vents at the Marianas Trough; Van Dover et al. (2001) reported Marianactis sp. from the Central

Indian Ridge in the Indian Ocean. The previously monotypic Cyananthea from the EPR is represented at the ELSC by C. hourdezi n. sp. Both species occupy areas where hydrothermal venting is diffuse and of low temperature. Alvinactis reu, another previously monotypic genus from the EPR, lives on or among aggregations of the siboglinid annelid tubeworm, Tevnia jerichonana Jones, 1985; its congener A. chessi n. sp. occupies rocky substrates at or near vents and colonizes the shells of the mussel

Bathymodiolus brevior von Cosel, Métivier and Hashimoto, 1994. Additionally,

Chondrophellia coronata is a cosmopolitan species found in many deep-sea habitats, 97 including vent sites on the EPR (Doumenc and Van-Praët 1988). At the ELSC, C. orangina n. sp. occupies a niche similar to that of C. coronata, which inhabits the rocky substrata both at the periphery of hydrothermal vents and areas of low-temperature diffusive venting. Although all collections were made away from vents, S. erythraios n. sp. was observed in video and photographs near diffusive venting (KAZ pers. obs.).

Amphianthus sp. has only been observed away from any obvious sources of venting.

The ELSC zoanthidean is very abundant on pillow basalts in areas of low temperature, diffuse venting. They have only been observed at the two northern sites,

Kilo Moana and TowCam. In their account of additional sites at the ELSC, Desbruyères et al. (1994) did not report any actiniarians, although they noted a “large number of small anemones” at the North Fiji Basin, 600 km west. These small anemones may be the undescribed zoanthidean, as all other ELSC sea anemone species collected in areas of diffuse flow are relatively large. The diffuse flow ELSC communities dominated by zoanthideans resembles diffuse flow communities on the northern and southern legs of the EPR dominated by the stauromedusa Lucernaria janetae Collins and Daly, 2005.

Both communities consist of dense assemblages of animals on the basalt substrate near fissures. Although sea anemones are primarily passive predators (Shick 1991), they may be able to take up dissolved organic matter (Schlichter 1982). The proximity of C. hourdezi n. sp., Alvinactis chessi n. sp., Actinostolidae sp., and the zoanthid to vent effluent suggests the possibility of an association with chemosynthetic bacteria; however, no such associations have been reported for actiniarians from chemosynthetic environments to date. In our examination of a specimen of C. hourdezi n. sp. we found a partially digested alvinocaridid shrimp, Chorocaris vandoverae Martin and Hessler, 1990, in the actinopharynx; these vent shrimp are abundant on or near dense beds of chemoautotrophic 98 mussels Bathymodiolus brevior. Other common inhabitants of the sea anemone community include the squat lobster Munidopsis lauensis Baba and de Saint Laurent, 1992, the bythograeid crabs Austinograea williamsi Hessler and Martin, 1989 and A. alayseae Guinot, 1989, gammarid amphipods, the holothurian Chiridota hydrothermica Smirnov, Gebruk, Galkin and Shank, 2000, and polynoid polychaetes (genera: Branchinotogluma, Harmothoe, and Levensteiniella). The barnacles Eochionelasmus ohtai Yamaguchi and Newman, 1997, Imbricaverruca yamaguchii Newman, 2000, and Vulcanolepas sp. are often intermixed with the zoanthid and the actiniarians on the rocky substrate. 99 Table 7: Hexacorallia from chemosynthetic environments.

Species Location Depth Habitat Record Zoanthidea Abyssoanthiidae Abyssoanthidae sp. Lau Basin 2700 vent 2 Abyssoanthus nankaiensis Nankai Trough 3259 seep 1 Actiniaria Actinostolidae Actinostola sp. Gulf of Mexico 540 seep 3 Actinostolidae sp. Lau Basin 1700-2700 vent 2 Anthosactis pearseae Monterey Canyon 2893 whale fall 4 Parasicyonis ingolfi Mid-Atlantic Ridge 3480 vent 5 Actinoscyphiidae Actinoscyphia sp. Gulf of Mexico 1070 seep 6 Alvinactis reu East Pacific Rise 2600 vent 7 Alvinactis chessi Lau Basin 1700-2700 vent 2 Cyananthea hydrothermala East Pacific Rise 2600 vent 8,9 Cyananthea hourdezi Lau Basin 1700-2700 vent 2 Maractis rimicarivora Mid-Atlantic Ridge 3650 vent 10 Marianactis bythos Marianas Trough 3660 vent 11 Marianactis sp. Central Indian ridge 2460 vent 12 Pacmanactis hashimotoi Manus Basin 1620 vent 13 Paractinostola sp. Monterey Canyon 580-1011 seep 14 Paranthosactis denhartogi Guaymas Basin 2025 vent 15 Stomphia sp. Monterey Canyon 580-1010 seep 14 Boloceroididae Boloceroides daphneae East Pacific Rise 2400-2650 vent* 16 Hormathiidae Amphianthus sp. Lau Basin 2700 vent 2 Chondrophellia coronata East Pacific Rise 2500 vent 8 Chondrophellia orangina Lau Basin 2700 vent 2 Monactis vestita Barbados Accretionary Prism 4980 mud volcano 17 Paraphelliactis pabista Guaymas Basin 2000 vent 9 Phelliactis callicyclus Guaymas Basin 2000 vent 9 Phelliactis hydrothermala East Pacific Rise 2524 vent 9 Kadosactiidae Monterey Canyon 3040 seep 9 Seepactis galkini Middle America Trench 3354-3795 seep 15** Sagartiidae Sagartiogeton erythraios Lau Basin 2700 vent 2 1) Reimer et al. 2007; 2) present study; 3) Bergquist et al. 2003; 4) Daly and Gusmão 2007; 5) Segonzac 1992; 6) MacDonald et al. 2003; 7) Rodríguez et al. in review; 8) Doumenc and Van Präet 1988; 9) Sanamyan and Sanamyan 2007; 10) Fautin and Barber 1999; 11) Fautin and Hessler 1989; 12) Van Dover et al. 2001; 13) López- González et al. 2005; 14) Barry et al. 1996; 15) López-González et al. 2003; 16) Daly 2006; 17) Olu et al. 1997. *Found 100 m from vents. ** Record synonymized as Seepaactis galkini by Sanamyan and Sanamyan (2007); however, this may represent a complex of species.

100 Acknowledgements.

Specimens were collected by KAZ and Stacy Kim, with the assistance from the crew of the R/V Melville, ROV Jason II, and supported through NSF Grant OCE

003403953 to C.R. Fisher. Comparative material was provided by R. Van Syoc of the

California Academy of Sciences, J. Voight of the FMNH, S. Cairns of the USNM, and O.

Tendal of the Zoological Museum of the University of Copenhagen. KAZ was supported through a Training Award for New Investigators (TAWNI) from the Biogeography of

Chemosynthetic Ecosystems (ChEss) project of the Census of Marine Life (CoML). MD and ER are supported by NSF EF-0531763; MD is also supported by NSF DEB 041527.

Notes

Estefanía Rodríguez and Marymegan Daly are coauthors on this manuscript, which is in press at Marine Biology Research. Both co-authors created figures and tables and assisted in writing and editing the manuscript. Marymegan Daly donated lab space, equipment, supplies and reagents.

Literature Cited

Barry JP, Gary Greene H, Orange DL, Baxter CH, Robison BH, Kochevar RE,

Nybakken JW, Reed DL, McHugh CM. 1996. Biologic and geologic

characteristics of cold seeps in Monterey Bay, California. Deep Sea Research Part

I: Oceanographic Research Papers 43:1739-1755.

Bergquist DC, Ward T, Cordes EE, McNelis T, Howlett S, Kosoff R, Hourdez S, 101 Carney R, Fisher CR. 2003. Community structure of vestimentiferan-generated

habitat islands from Gulf of Mexico cold seeps. Journal of Experimental Marine

Biology and Ecology 289:197-222.

Carlgren O. 1928. Actiniaria der Deutschen Tiefsee-Expedition. Wissenschaftliche

Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer "Valdivia" 1898-

1899 4:125-266 [reprint 1-144].

Carlgren O. 1942. Actiniaria, part II. Danish Ingolf Expedition 5:1-92.

Carlgren O. 1949. A survey of the Ptychodaria, Corallimorpharia and ActiniariaC.

Kungliga Svenska Vetenskapakademiens Handlingar 1:1-121.

Carlgren O. 1956. Actiniaria from depths exceeding 6000 meters. Galathea Report

2:9-16.

Corliss JB, Dymond J, Gordon LE, Edmond JM, von Herzen RP, Ballard RD, Green

K, Williams D, Bainbridge A, Crane K, van Andel TH. 1979. Submarine thermal

springs on the Galapagos Rift. Science 203:1073-1083.

Daly M. 2006. Boloceroides daphneae, a new species of giant sea anemone

(Cnidaria: Actinaria: Boloceroididae) from the deep Pacific. Marine Biology

148:1241-1247.

Daly M, Gusmão L. 2007. The first sea anemone (Cnidaria: Anthozoa: Actiniaria)

from a whale fall. Journal of Natural History 41:1-11.

Desbruyères D, Hashimoto J, Fabri M-C. 2006a. Composition and biogeography of

hydrothermal vent communities in Western Pacific Back-Arc Basins. Chapter in:

Christie DM, Fisher CR, Lee S-M, Givens S, editors. Back-Arc Spreading 102 Systems: Geological, Biological, Chemical, and Physical Interactions. Washington

D.C.: American Geophysical Union, p 215-234.

Desbruyères D, Segonzac M, Bright M. 2006b. Handbook of Deep-Sea Hydrothermal

Vent Fauna (2nd ed). Vienna: Denisa. 544 pages.

Desbruyères D, Alayse-Danet A-M, Ohta S, Scientific Parties of BIOLAU and

STARMER cruises. 1994. Deep-sea hydrothermal communities in Southwestern

Pacific back-arc basins (the North Fiji and Lau Basins): composition,

microdistribution and food web. Marine Geology 116:227-242.

Doumenc D, Van-Praët M. 1988. Actinies abyssales d'un site hydrothermal du

Pacifique oriental. Oceanologica Acta, special 8:61-68.

Fautin DG. 2007. Hexacorallians of the World. Available from:

http://hercules.kgs.ku.edu/hexacoral/anemone2/index.cfm/ (18 December 2007).

Fautin DG, Barber BR. 1999. Maractis rimicarivora, a new genus and species of sea

anemone (Cnidaria: Anthozoa: Actinaria: Actinostolidae) from an Atlantic

hydrothermal vent. Proceedings of the Biological Society of Washington 112:624-

631.

Fautin DG, Hessler RR. 1989. Marianactis bythios, a new genus and species of

actinostolid sea anemone (Coelenterata: Actiniaria) from the Mariana vents.

Proceedings of the Biological Society of Washington 102:815-825.

Fautin DG, Zelenchuck T, Raveendran D. 2007. Genera of orders Actiniaria and

Corallimorpharia (Cnidaria, Anthozoa, Hexacorallia), and their type species.

Zootaxa 1668:183-244. 103 Fisher C, Roberts H, Cordes E, Bernard B. 2007a. Cold seeps and associated

communities of the Gulf of Mexico. Oceanography 20:68-79.

Fisher CR, Takai K, Le Bris N. 2007b. Hydrothermal Vent Ecosystems.

Oceanography 20:18-27.

Govenar B, Fisher CR. 2007. Experimental evidence of habitat provision by

aggregations of Riftia pachyptila at hydrothermal vents on the East Pacific Rise.

Marine Ecology 28:3-14.

Levin LA. 2005. Ecology of cold seep sediments: interactions of fauna with flow,

chemistry and microbes. Oceanography and Marine Biology: An Annual Review

43:1-46.

López-González PJ, Rodríguez E, Segonzac M. 2005. A new species of sea anemone

(Cnidaria: Anthozoa: Actiniaria) from Manus Basin hydrothermal vents, South-

western Pacific. Marine Biology Research 1:326-337.

López-González PJ, Rodríguez E, Gili JM, Segonzac M. 2003. New records on sea

anemones (Anthozoa: Actinaria) from hydrothermal vents and cold seeps.

Zoologische Verhandelingen Leiden 345:215-243.

MacDonald IR, Sager WW, Peccini MB. 2003. Gas hydrate and chemosynthetic biota

in mounded bathymetry at mid-slope hydrocarbon seeps: Northern Gulf of

Mexico. Marine Geology 198:133-158.

Mariscal RN. 1974. Nematocysts. Chapter in: Muscatine L, Lenhoff HM, editors.

Coelonterate Biology: Reviews and New Perspectives. New York: Academic

Press. p 129-178. 104 Nelson DC, Fisher CR. 1995. Chemoautotrophic and methanotrophic endosymbiotic

bacteria at deep-sea vents and seeps. Chapter in: Karl DM, editor. Microbiology of

the Deep-Sea Hydrothermal Vent Habitats. Boca Raton: CRC Press. p 125-167.

Olu K, Lance S, Sibuet M, Henry P, Fiala-Medioni A, Dinet A. 1997. Cold seep

communities as indicators of fluid expulsion patterns through mud volcanoes

seaward of the Barbados accretionary prism. Deep Sea Research Part I:

Oceanographic Research Papers 44:811-819.

Presnell JK, Schreibman MP. 1997. Humason's Animal Tissue Techniques.

Baltimore: John Hopkins University Press. 572 pages.

Reimer JD, Sinniger F, Fujiwara Y, Hirano S, Maruyama T. 2007. Morphological and

molecular characterization of Abyssoanthus nankaiensis, a new family, new genus

and new species of deep-zoanthid (Anthozoa: Hexacorallia: Zoantharia) from a

north-west Pacific methane cold seep. Invertebrate Systematics 21:255-262.

Riemann-Zürneck K. 1987. Amphianthus bathybium Hertwig, 1882 aus der

Iberischen Tiefsee. Redeskription der Typusart (Actiniaria: Hormathiidae).

Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 84:7-15.

Riemann-Zürneck K. 1991. The abyssal sea anemone Kadosactis sulcata Carlgren,

1934 (Cnidaria: Actiniaria: Kadosactidae nov. fam.). Mitteilungen aus dem

Hamburgischen Zoologischen Museum und Institut 21:191-204.

Rodríguez E, López-González PJ. 2005. New record of the sea anemone Kadosactis

antarctica (Carlgren, 1928): re-description of an Antarctic deep-sea sea anemone,

and a discussion of its generic and familial placement. Helgoland Marine Research

59:301-309. 105 Rodríguez E, Castorani CN, Daly M. Morphological phylogeny of family

Actinostolidae (Anthozoa: Actiniaria) with a description of a new genus and

species of hydrothermal vent sea anemone. Invertebrate Systematics (in review).

Sanamyan NP, Sanamyan KE. 2007. Deep-water Actiniaria from East Pacific

hydrothermal vents and cold seeps. Invertebrate Zoology 4:83-102.

Schlichter D. 1982. Nutritional Strategies of Cnidarians - the Absorption,

Translocation and Utilization of Dissolved Nutrients by Heteroxenia-Fuscescens.

American Zoologist 22:659-669.

Segonzac M. 1992. Les peuplements associés à l'hydrothermalisme océanique du

Snake Pit (dorsale médio-atlantique; 23ºN, 3480 m): composition et

microdistribution de la mégafaune. Comptes Rendus de l'Academie des Sciences

Série III 314:593-600.

Shick JM. 1991. A Functional Biology of Sea Anemones. London: Chapman and

Hall. 375 pages.

Smith CR, Baco AR. 2003. Ecology of whale falls at the deep-sea floor.

Oceanography and Marine Biology: An Annual Review 41:311-354.

Tunnicliffe V, Fowler MRC. 1996. Influence of sea-floor spreading on the global

hydrothermal vent fauna. Nature 379:531-533.

Tyler PA, German CR, Ramirez-Llodra E, Van Dover CL. 2003. Understanding the

biogeography of chemosynthetic ecosystems. Oceanologica Acta 25:227-241.

Van Dover CL, Humphris SE, Fornari D, Cavanaugh CM, Collier R, Goffredi SK,

Hashimoto J, Lilley MD, Reysenbach AL, Shank TM, Von Damm KL, Banta A,

Gallant RM, Götz D, Green D, Hall J, Harmer TL, Hurtado LA, Johnson P, 106 McKiness ZP, Meredith C, Olson E, Pan IL, Turnipseed M, Won Y, Young CR,

Vrijenhoek RC. 2001. Biogeography and ecological setting of Indian Ocean

hydrothermal vents. Science 294:818-823.

Williams RB. 1998. Measurements of cnidae from sea anemones (Cnidaria:

Actiniaria), II: further studies of differences amongst sample means and their

taxonomic relevance. Scientia Marina 62:361-372.

Williams RB. 2000. Measurements of cnidae from sea anemones (Cnidaria:

Actinaria), III: ranges and other measures of statistical dispersion, their

interrelations and taxonomic relevance. Scientia Marina 64:49-68.

107 CHAPTER 3

Community Structure of Hydrothermal Vent Communities at the East-Lau Spreading

Center, Southwest Pacific

ABSTRACT

We examined the communities associated with three potential foundation species that harbor chemoautotrophic endosymbionts (Alviniconcha sp., Ifremeria nautilei, and

Bathymodiolus brevior) at four sites along the Eastern Lau Spreading Center (ELSC).

The four study sites, Kilo Moana, TowCam, ABE, and Tu’i Malila, are distributed over

200 km along a north-south geologic gradient that corresponds to changes in the tectonic setting, seafloor morphology and vent fluid chemistry. Expected species richness and

Shannon diversity index at the southern sites relative to the northern sites. Communities of the southernmost site, Tu’i Malila, were structured differently than the rest of the sites and characterized by lower abundances of associated fauna and many rare and uncommon species. The two northern sites, Kilo Moana and TowCam, had similar community structure characterized by low diversity and low Pielou’s evenness. ABE had a community structure between the northern sites and Tu’i Malila. Communities associated with Alviniconcha sp. were lower in abundance and lower in species richness, but had greater Pielou’s evenness, than other foundation species types. Foundation species type plays a larger role in how communities are assembled at ELSC hydrothermal vents as evidenced by the strength of multivariate comparisons, in comparison to the inherent covarying geological characteristics associated with being at a particular site.

108 INTRODUCTION

Dayton (1972) defined a foundation species as a large, influential species that has a positive effect on most community inhabitants through modifying environmental parameters, species interactions and resource availability. Bruno and Bertness (2001) further characterized a foundation species as one that increases the fitness of most associated faunal populations by ameliorating the habitat in some way due to its presence, not its actions. A foundation species’ presence may facilitate a community by providing habitat complexity, altering the physical or chemical environment, providing a refuge from predation or enhancing recruitment (Bruno et al. 2003). Each of these benefits is predicted to expand the realized niche of species and increase the fitness of the populations living within the community (Bruno et al. 2003).

Chemoautotrophic symbiont-hosting invertebrates at hydrothermal vents may be foundation fauna that live in environments with high concentrations of toxic chemicals and heavy metals, low oxygen concentrations, and high temperatures. For example, vestimentiferan tubeworms provide structural heterogeneity (Govenar et al. 2005,

Govenar & Fisher 2007, Shank et al. 1998, Tsurumi & Tunnicliffe 2003), bathymodiolin mussels divert diffuse hydrothermal flow and remove hydrogen sulfide from the environment (Fisher et al. 1988, Johnson et al. 1986, 1988, 1994). The result is an environment amenable to colonizers less tolerant of direct exposure to vent fluids (Shank et al. 1998) and an increased standing stock biomass relative to the ambient deep seafloor

(Fisher 1996). The mussels and snails of ELSC can reduce the presence of hydrogen sulfide (Henry et al. 2008, Waite et al. 2008), increase habitat heterogeneity and may also disperse diffuse hydrothermal flow around their aggregations. 109 Back-arc basins are unique environments that result from extensional forces at the convergent boundary between two or more oceanic plates. The western boundary of the

Pacific plate contains nearly 7,000 km of back-arc basin spreading ridges (Bird 2003). At the Eastern Lau Spreading Center (ELSC) in particular there are several important trends along the ridge axis. The rate of seafloor spreading increases northward from 39 mm/yr to 96 mm/yr (Zellmer & Taylor 2001), crustal thickness decreases northward, distance from the volcanic arc increases northward corresponding to a more MOR-like basalt substratum in the north to a more andesitic substratum in the south (Martinez & Taylor

2003, Ferrini et al. 2008), and axial highs in the southern ELSC transition to axial lows in the northern ELSC (Martinez et al. 2006). These characteristics tend to alter the rugosity of the seafloor, from the more brittle and smooth andesitic substrata to the hard and rougher basaltic substrata, as well as alter the hydrothermal fluid chemistry (Ferrini et al.

2008).

Hydrothermal vents occur at mid-ocean spreading centers around the world, forming several unique biogeographic provinces based upon species composition (Tyler et al.

2003, Bachraty et al. 2009). Faunal communities at back-arc basins were surveyed beginning with the Manus Basin (Both et al. 1986, Galkin 1997) and the later the

Okinawa Trough (Ohta 1990), Marianas Trough (Hessler & Lonsdale 1991), Lau and

North Fiji Basins (Desbruyères et al. 1994). Hessler and Lonsdale (1991) noted that communities were very similar over large geographic distances at back-arc basins. Using a much more comprehensive dataset from all known deep-sea vent communities at the time publication, Desbruyères et al (2006a) corroborated this pattern using multivariate comparative techniques. 110 This study aims to address the question of how communities are structured along the

ELSC ridge axis and, at a finer scale, how communities are structured by the presence of foundation species types at ELSC. The hypothesis that communities are structured along the ELSC ridge axis was tested by comparing quantitatively collected whole community samples from four study sites along the ELSC. The sites span nearly 220 km and encompass the north to south geologic gradients discussed above. The hypothesis that communities are structured by foundation species type was tested by analyzing and comparing quantitatively collected whole community samples associated with three chemoautotrophic symbiont-containing invertebrates: Alviniconcha sp., Ifremeria nautilei, and Bathymodiolus brevior. For the purposes of this study I will consider these species as foundation species because the net effect of their presence may ameliorate the habitat by filtering toxic hydrogen sulfide from the vent source (Henry et al. 2008, Waite et al. 2008), provide habitat complexity, and expand the niche range for other associated invertebrates.

MATERIALS & METHODS

Collections – Samples of Bathymodiolus brevior, Ifremeria nautilei and Alviniconcha sp. and their associated communities were collected using the ROV JASON II, in conjunction with the R/V Melville, during the June 2005 (TUIM07MV) and September

2006 (MGLN06MV) expeditions to the Eastern-Lau Spreading Center. Our sampling localities (Fig. 1), from north to south, were: Kilo Moana (176°08.03’W, 20°03.15’S,

2620 m water depth), TowCam (176°08.2’W, 20°19.0’S, 2700 m water depth), ABE

(176°11.5’W, 20°45.8’S, 2140 m water depth) and Tu’i Malila (176°34.06’W, 111 21°59.35’S, 1870 m water depth).

Figure 1: Topographic map of the Lau Basin with collection sites indicated courtesy of the Ridge Multibeam Synthesis Data Portal of the Marine Geoscience Data System.

Community samples were obtained using a collection apparatus modified from a design by Van Dover (2002). This “mussel/snail pot” (Fig. 2, hereafter MP) had a 25 cm diameter, 30.5 cm height and internal volume of 0.015 m3. The mechanical arm of the

ROV turns the handle to cinch closed a Kevlar (2005 and 2006 samples) or Vectran

(2006 samples) skirt and release an outer ring (Fig. 2) that allowed us to evaluate the 112 collection efficiency. The number of foundation fauna left behind in the ring was divided by the sum of the number of individuals in the MP plus the ring in order to estimate the proportion that was collected after stowing the MP on the ROV. Our collections captured

60-100% of the foundation fauna within the perimeter of the ring. There were no differences in collection efficiency between site (P = 0.8) or foundation fauna type (P =

0.1).

Figure 2: Schematic diagram of the “mussel/snail pot” collection device. Drawing provided by G. Telesnicki.

All fauna associated with each mussel pot were preliminarily identified, sorted, and fixed in seawater-buffered formalin (cnidarians, polychaetes, flatworms and mollusks) then transferred to 70% ethanol or fixed directly into 70% ethanol (crustaceans and echinoderms). In the laboratory, individuals were counted and fixed wet weights were determined. Total biomass (wet weight) of the associated fauna and species richness (total number of species) were estimated for each collection. Shannon diversity index was 113 calculated as one measure of species diversity for each collection:

S

H " = #% pi $ loge (pi ), i where pi is the relative abundance of the ith species summed up to S, the maximum ! number of species in a collection. Pielou’s evenness index was calculated as a measure of how evenly distributed the relative abundances of fauna were in a collection:

H " J " = , Hmax where Hmax is the theoretical maximum value for H’ if every species in a collection were ! equally abundant.

Biomasses were estimated for Alviniconcha sp., Ifremeria nautilei, and

Bathymodiolus brevior from a regression of shell width to wet weight. Individuals were counted and shell width, height and length was measured onboard the ship. A subset of

10-15 individuals of each species, representative of the size range in the collections, was drained of seawater and blotted dry. Snails were weighed in shell and mussel tissue was dissected out the shell and weighed using a motion-compensated balance (Childress &

Mickel 1980). Widths were determined by regression to be the best single indicator of wet weight. Mussel shell width was measured as the distance (mm) between the maximum points of inflation of each valve in the closed position. For each gastropod, width was measured as the distance from the apex to the widest point on the aperature. Biomass of each individual snail and mussel was estimated from shell widths by the following set of equations: 114

B. brevior: wet weight = (2.53 × width) – 56.9; R2 = 0.86,

I. nautilei: wet weight = (0.91 × width) – 22.3; R2 = 0.86,

Alviniconcha sp.: wet weight = (1.82 × width) – 69.2; R2 = 0.97.

Shell surface area of the foundation fauna in a collection was calculated using a standard formula for the surface area of an ovoid. An ovoid was chosen because it most closely resembled the elliptical three-dimensional morphology of mussels and snails.

Width and length of each mussel and snail shell in a collection were used to estimate the total shell surface area for the ith individual to N, the maximum number of individuals in a collection.

4 N # 1 & # 1 & 2 S.A.= ")% length( *% width( . 3 i $ 2 ' $ 2 '

Condition Index !– Mussels respond to changes in the environment by losing or gaining mass and water content, which is correlated with habitat quality (Crosby & Gale 1990).

The ratio of ash-free dry weight (AFDW) to shell volume and percent water in the tissues were determined as indices of physiological condition (Smith 1985, Fisher et al. 1988) for a subsample of 10-15 individuals of B. brevior from each collection. Because the mass to volume ratio varies with the size of the animal, the residuals of the log AFDW to log shell volume regression were analyzed (Jakob et al. 1996). Mussels were drained of seawater and the body tissue and hemolymph were removed and weighed at sea, then 115 stored frozen at -70°C. In the lab, mussel tissue and hemolymph were dried at 60°C to constant weight (± 1.0 mg). Percent water was calculated from the wet and dry weights:

% Water = {(wet weight - dry weight) ÷ wet weight} × 100.

Dried tissue was combusted at 500°C for 24 hours to remove volatile organic material.

The resulting ash deposit was weighed and subtracted from the dry weight to determine the mass of the organic constituents of the tissue (AFDW):

AFDW = Dry weight – Ash weight.

Shell volume was determined in the laboratory by filling each shell valve with distilled water and measuring the volume in a graduated cylinder (± 0.5 mL). Leaks and cracks in the shell were first repaired with hot glue on the shell’s exterior.

Analysis – Samples were pooled by site (N = 4) or foundation fauna type (N = 5) for statistical analyses. Most of the MP collections were dominated (86% or greater) in both biomass and abundance by a single species of foundation fauna. Although areas visually dominated by a single species of foundation fauna were normally targeted for collections, after collection two mixed foundation fauna categories were added as factors in the analyses: B. brevior/I. nautilei and Alviniconcha sp./I. nautilei. A community is defined as “mixed” if one foundation fauna species makes up at most 75% and another making up at least 25% of the abundance and biomass of the collection. There were no collections of mixed of Alviniconcha sp. and B. brevior communities.

The Shapiro-Wilk test was used to test the normality of the continuous variables.

Abundances of foundation fauna as well as abundances and biomasses of associated fauna failed to fit a normal distribution and were log-transformed (abundances) or square 116 root-transformed (biomass) to meet the assumption of normality. Nonparametric tests were used for variables that rejected the normality assumption. These statistical tests were carried out using Stata/IC 10.0 for Macintosh ( 2008 Stata Corporation, College

Station, TX, USA).

To test the significance of the relationship between two continuous variables linear regression was used. One-way analysis of variances (ANOVA) was used to test for significant differences among sites and among foundation fauna types. Tukey’s post hoc pairwise comparisons were conducted after an ANOVA to test which sites or foundation fauna types were significantly different from each other. P-values are reported after making a strict Bonferroni correction for multiple comparisons when applicable.

Rarefaction curves, Shannon diversity and Pielou’s evenness were calculated using

EstimateS (Colwell 2006).

To assess similarities in community structure among sites and among foundation fauna types, the Bray-Curtis similarity coefficient was calculated:

$ p ( & # yij " yik & & i=1 & S jk =100% 1 " p ) & y + y & & #()ij ik & ' i=1 * based on quarter-root transformed densities (Clarke & Warwick 2001), where Sjk is the similarity between samples! j and k, yij is the density of species i in sample j, yik is the density of species i in sample k, and p is the total number of species. The software

PRIMER (version 5.2.9 © 2002 PRIMER-E Ltd., Plymouth, UK) was used to conduct analyses of community structure. To test for global and pairwise differences in community similarity the ANOSIM (analysis of similarity) procedure was performed 117 with 1000 permutations. To estimate the cumulative percentage each species contributes among collections grouped by site or foundation fauna type the SIMPER (similarity percentages) procedure was performed. Multi-dimensional scaling (MDS) plots were constructed using the Bray-Curtis similarity coefficient with 100 permutations to evaluate patterns in community structure among sites and among foundation fauna types.

RESULTS

Sampling Effort – Among the 36 successful quantitative collections (Table 1), 51,757 individuals were collected. In general, our collection effort was able to capture a representative portion of the ELSC species pool (Fig. 3a: solid black line), but variations among sites and among foundation species types exist (Fig. 3).

While the rate of species accumulation is relatively similar among sites there are three tiers pertaining to the expected species richness (Fig. 3a). Sampling effort at Kilo

Moana and TowCam were very similar, yet only the curve for Kilo Moana has leveled.

The southern sites, Tu’i Malila and ABE, have not leveled off and both have higher expected species richness than the northern sites. The sampling effort curve at ABE (Fig.

3a) closely tracks the curve for the pooled total and shows signs that further sampling of chemoautotrophic communities there may yield additional species.

Separating the sampling effort curves by foundation fauna type shows differences in expected species richness associated with each community type: Alviniconcha sp. > I. nautilei > I. nautilei/B. brevior > B. brevior > Alviniconcha sp./I. nautilei (Fig. 3b).

Further sampling would likely yield additional species in all communities. In particular,

Alviniconcha sp./I. nautilei mixed communities are undersampled. 118

Figure 3: Sampling effort curves among a) sites and b) foundation fauna types

119 Table 1: Mean abundance pooled by site (left side) and by foundation fauna type (right side) collected in mussel/snail pots. Bolded rows are the chemoautotrophic foundation fauna. ‘P’ denotes presence.

Kilo Tu'i Alvin/ Bathy/ Moana TowCam ABE Malila Alvin Ifrem Ifrem Ifrem Bathy No. Samples 12 7 11 6 8 3 10 6 9 PLATYHELMINTHES Polycladida sp. 0 0 0.3 0 0.4 0 0 0 0 MOLLUSCA Bathymodiolus brevior 8 9.5 11.3 20.5 0 0 2.7 20.8 35.9 Clam 0 0 0.1 0.3 0 0 0.1 0 0.3 Helicoradomenia sp. 0 0 0.4 0 0 0 0.1 0.7 0

Gastropoda Alviniconcha hessleri 12.6 3.3 11.1 35.6 65.9 21.3 2.0 0.2 2.3 Bathyacmaea sp. 0 0.2 0.1 38.4 3.6 0.3 36.8 0 2.9 Bruciella globulus 0 0 0.5 0 0 0 0 1.0 0 Desbruyeresia cancellata 0.4 0.2 2.8 3 0.1 0.3 0.6 4.8 3.7 Eosipho desbruyeresi 0.3 0 0.5 0.4 0 0 0.3 1 0.3 Ifremeria nautilei 12.7 24.3 50.4 31.6 2.8 45.0 70.9 46.3 4.9 Laeviphitus sp. 0 0 0 0.1 0 0 0.1 0 0 Lepetodrilus schrolli 1162.1 1994.3 1306.5 170.7 37.3 1466.7 706.8 1387.2 1952.0 Leptogyra inflata 0 0 0.1 0 0 0 0 0 0.1 Lurifax sp. 0 0 0 0.4 0.3 0 0 0 0.2 Olgasolaris tollmanni 17.3 65.3 105.1 492.1 27.6 45.7 412.2 122.3 219.2 Pachydermia sculpta 0 0.2 0.2 0 0 0.3 0 0.3 0 Phymorhynchus sp. 0 0.2 0.2 0.1 0 0 0 0.5 0.1 Planorbidella depressa 0.1 0 0 0.1 0.3 0 0 0 0 Provanna buccinoides 0 0 0.5 0 0 0 0.2 0.7 0 Pseudorimula marianae 0 0.5 3.9 2 0 0 0.5 7.8 2.2 Shinkailepas sp. 0.1 0.2 1.1 2.5 0 1.3 0.9 1.2 2.6 Symmetromphalus sp. 0.4 17.2 44.8 6.9 1.1 160 20.9 2.5 0.7 Ventsia tricarinata 0 0 0.2 0.1 0 0 0.1 0.2 0.1

ANNELIDA Polychaeta Amphisamytha galapagensis 12.7 31.7 75.2 3.2 12.3 229.7 29.8 10.7 7.4 Archinome rosacea aff. 0.1 10.5 4.3 4.9 0.4 0.7 0.7 13.5 8.6 Branchinotogluma sp. nov. 0 0.5 0.3 0 0 0 0 0.5 0.3 Branchinotogluma marianus 1.7 1.7 2.8 0.6 0.3 1.7 3.3 2.7 0.7 Branchinotogluma trifurcus 4.9 10.3 43.9 40.6 4.3 39 63.4 35.8 7.8 Branchipolynoe pettiboneae 0.4 1 6.3 3.2 0.1 0 1.1 6.3 7.7 Capitellidae sp. 0 0.2 1 0.1 0 0.3 0.1 1.8 0.1 Hesiospina sp. 0.1 0.7 7 4.8 1.3 13.3 2.9 3.8 4.4 Lepidonotopodium minutum 1.1 2.5 7.7 2.2 0.3 5.3 8.9 3.8 1 Maldanidae sp. 0 0 0.1 0.2 0 0 0 0 0.3 Nereididae sp. 0 0 0.3 0 0 0 0.2 0.2 0 Oasisia fujikurai aff. 0 p 0 0 p 0 p 0 0 Paralvinella fijiensis 0 0 0.8 0.4 1.1 0 0.2 0.3 0 Paralvinella unidentata 0 0 22.1 2.6 3.4 80.3 2.5 0.2 0 Prionospio sp. 0 0 1.3 0.1 0 0 0 2.2 0.3 120

Thermiphione fijiensis 0 0 0.1 0 0 0 0 0.2 0 Thermopolynoe branchiata 0.3 0.2 3.1 0.9 1 6.7 1 0.8 0.8 Thraumastros dieteri 0 0 1.2 0 0 0 0 2.3 0 ARTHROPODA Cumacea sp. 0 0 0.9 0 0 0 0 0 1.2 Gammaridae sp. 0 0 0 0.3 0.1 0 0 0 0.2 Gnathiidae sp. 0 0 0 0.2 0 0 0.1 0 0.1 Ostracoda sp. 0.1 0 0 0 0.1 0 0 0 0 Stygiopontius lauensis 0 0 6.1 95.7 131 24.3 0.1 0 0.4 Decapoda Alvinocaris komaii 2.1 0 0 0 0 0 0 0 1.7 Austinograea alayseae 0.7 0.5 0.7 3.3 3 0 1.8 1 0.4 Austinograea williamsi 0.7 0.8 0.5 0.5 0.8 0.7 0.6 0.3 0.6 Chorocaris vandoverae 10 7.7 21.1 14.4 22 34 15.7 9.2 4.1 Munidopsis lauensis 0 0 0.3 0 0 0 0.2 0 0.2 Nautilocaris saintlaurentae 0 0 0.1 0 0 0 0 0 0.1 Cirripedia Eochionelasmus ohtai 2.6 0.8 9.3 13.3 0 0 1.8 2.8 27.2 Imbricaverruca yamaguchii 0 0 0.2 0.1 0.1 0 0 0.3 0 ECHINODERMATA Chiridota hydrothermica 0 0.3 0 0 0 0 0 0.3 0

121 To test the hypothesis that our measures of community structure were explained by differences in the collection efficiency, the relationship between collection efficiency and several community parameters was determined by regression. While trends exist between collection efficiency and associated fauna abundance or biomass, foundation fauna abundance or biomass, shell surface area, species richness, Shannon diversity index, or Pielou’s evenness index, no statistical significance was detected in the data (P >

0.07, strict Bonferroni correction applied for multiple comparisons). Additionally, collection efficiency was not significantly different among sites or among foundation fauna types (P > 0.1).

Table 2: Abundance and biomass of foundation fauna or associated fauna at each site or foundation fauna type. Mean Mean Mean Mean No. Abundance Biomass Abundance Biomass Samples Foundation Foundation Associated Associated Fauna* Fauna (g) Fauna* Fauna (g) Site a Kilo Moana 7 33 1124.8 1217 40.1 ab Two Cam 6 37 977.8 2148 69.0 ab ABE 12 73 1583.7 1686 56.3 b Tu'i Malila 11 88 1799.7 909 43.6 Community Type a Alviniconcha 8 69 1511.0 253 62.1 b Ifremeria 10 76 1480.5 1315.5 49.7 b Bathymodiolus 9 43 1401.8 2258.67 57.0 b Ifrem/Bathy 6 67 1537.4 1629.83 39.7 b Alvin/Ifrem 3 66 1403.2 2116 59.1 Significance is determined by one-way ANOVA with P < 0.05. * ANOVA computed using log-transformed data

122 Community Composition – The collections from Kilo Moana had significantly lower foundation fauna abundance than those from Tu’i Malila (Table 2: P = 0.02). Mean abundance of associated fauna in the Alviniconcha sp. collections was significantly lower than all other foundation fauna types (P < 0.04), while there was no difference in mean biomass (Table 2).

Mean biomass and shell surface area of foundation fauna in the collections were not significantly different among sites (P > 0.1; Table 2). Four taxa made up 69% or greater of the associated fauna biomass at all sites (Table 3): the limpets Lepetodrilus schrolli (5.7-49.5%) and Olgasolaris tollmanni (7.9-30.4%), the shrimp Chorocaris vandoverae (6.8-20%) and crab Austinograea alayseae (5.9-39.4%). Austinograea williamsi was present in high biomass at Kilo Moana (11.4%) and TowCam (12.5%). The polychaete annelid Thermopolynoe branchiata had its highest biomass at ABE (12.6%) and the gastropod Eosipho desbruyeresi had its highest biomass at Tu’i Malila (5.4%), relative.

Three taxa were among the top five contributors to the biomass of the associated fauna in all foundation fauna types (Table 4): Lepetodrilus schrolli (4.0-45.1%),

Olgasolarus tollmanni (7.2-31.7%) and Chorocaris vandoverae (3.9-15.2%).

Austinograea williamsi was a significant biomass contributor in only Alviniconcha sp. communities where it made up 21.2% of the associated fauna biomass. A. williamsi and

A. alayseae together made up 70.2% of the biomass of the Alviniconcha sp. associated fauna. Branchipolynoe pettiboneae is a polynoid polychaete living commensally in the mantle cavity of bathymodiolin mussels (Miura & Hashimoto 1991). In communities where Bathymodiolus brevior made up at least 25% of the foundation fauna density B. 123 pettiboneae was a large contributor (6.8-11%) to the biomass of the associated fauna.

Where Ifremeria nautilei comprised at least 25% of the foundation fauna density

Branchinotogluma trifurcus, another polynoid polychaete, was a large contributor (7.3-

8.2%) to the biomass of the associated fauna. The barnacle Eochionelasmus ohtai only

made a large contribution (16.4%) to the associated fauna biomass in B. brevior

communities, where it was attached to the mussel shells (Table 4).

Table 3: Cumulative biomass of species in collections at each study site.

Kilo Moana TowCam ABE Tu'i Malila Species Cum. % Species Cum. % Species Cum. % Species Cum. % Lepetodrilus schrolli 48.4 L. schrolli 49.5 L. schrolli 38.0 A. alayseae 39.4 Chorocaris O. vandoverae 68.4 tollmanni 65.6 O. tollmanni 52.6 O. tollmanni 69.8 Austinograea Thermopolynoe C. williamsi 79.8 A. williamsi 78.1 branchiata 65.2 vandoverae 76.6 Olgasolaris C. tollmanni 87.7 vandoverae 88.7 C. vandoverae 75.6 L. schrolli 82.1 Austinograea Eosipho alayseae 93.8 A. alayseae 95.1 A. alayseae 81.5 desbruyeresi 87.5

Table 4: Cumulative biomass of species in collections of each foundation fauna type. Alviniconcha Ifremeria Bathymodiolus Species Cum. % Species Cum. % Species Cum. % Austinograea alayseae 49.0 O. tollmanni 31.3 L. schrolli 45.1 Eochionelasmus Austinograea williamsi 70.2 L. schrolli 52.9 ohtai 61.4 Branchipolynoe Chorocaris vandoverae 85.4 A. alayseae 66.3 pettiboneae 72.4 Olgasolaris tollmanni 92.6 C. vandoverae 76.5 O. tollmanni 82.7 Lepetodrilus schrolli 96.6 B. trifurcus 84.7 C. vandoverae 88.6

Alvin/Ifrem Bathy/Ifrem Species Cum. % Species Cum. % L.schrolli 42.1 L. schrolli 38.9 O. tollmanni 73.8 O. tollmanni 61.6 C. vandoverae 84.3 A. alayseae 77.5 Branchinotogluma trifurcus 91.0 C. vandoverae 84.3 Amphisamytha sp. 96.2 B. pettiboneae 90.4

124

In general, the ANOSIM results indicated that variation in community similarity among sites using associated fauna biomass or abundance data was comparable to variation in similarity among collections within a site (Table 5). Collections from Tu’i

Malila had a significantly different species abundance composition than all other sites (R

> 0.3, P > 0.01) and collections from ABE had a significantly different species abundance composition than Kilo Moana (R = 0.26, P = 0.02). The community similarity among collections within a site ranged from 32.2% at Kilo Moana to 43.5% at Tu’i Malila. In pairwise comparisons between sites, the greatest Bray-Curtis similarity using associated fauna biomasses is between Kilo Moana and TowCam (40.9%) as well as ABE and

TowCam (40.6%). The lowest Bray-Curtis similarity using associated fauna biomasses was between Kilo Moana and Tu’i Malila (27.7%; Table 3). Using associated fauna abundance data, Bray-Curtis similarity among collections within a site ranged between

53.1% at ABE to 60.4% at TowCam. Pairwise comparisons of Bray-Curtis similarity between sites using associated fauna abundances showed a similar pattern to the associated fauna biomass data. The greatest Bray-Curtis similarity between communities using associated fauna abundance occurred between Kilo Moana and TowCam (57.3%), whereas the lowest Bray-Curtis similarity occurred between Kilo Moana and Tu’i Malila

(43.2%; Table 5).

Based on the ANOSIM analysis, the communities associated with each

“unmixed” foundation fauna types were significantly different from the other two foundation fauna types (Table 6). Using associated fauna biomass data, Bray-Curtis similarity tended to be lower among community types than among collections within a 125 community type. Bray-Curtis similarity within community types among collections ranged from 37.5% in Bathymodiolus brevior communities to 48.3% in Ifremeria nautilei communities. Bray-Curtis similarity between Alviniconcha sp. communities and other foundation fauna types was generally low, ranging from 19.7% with B. brevior communities to 33.2% with I. nautilei communities. The greatest Bray-Curtis similarity between foundation fauna types occurred with I. nautilei and mixed I. nautilei/B. brevior at 46.6% (Table 6). In general, variation in Bray-Curtis similarity using associated fauna abundance data among community types was comparable to variation in Bray-Curtis similarity among collections within community types. Bray-Curtis similarity of communities based on associated fauna abundances within each type ranged from 48.3% in Alviniconcha sp. communities to 61.4% in I. nautilei communities. In pairwise comparisons between community types based on associated fauna abundances Bray-

Table 5: Results of ANOSIM using species’ abundances among sites. No sites were significantly different from another at the P < 0.05 significance level, therefore statistical results are not shown. Percent similarity of species’ biomasses and species’ abundances reported between sites (above the line) and among collections from a site (below the line). % Similarity Kilo Moana vs Biomass Abundance TowCam 40.9 57.3 ABE 34.1 49.5 Tu'i Malila 27.7 43.2 TowCam vs ABE 40.6 53.2 Tu'i Malila 33.4 46.2 ABE vs Tu'i Malila 33.3 49.1 Kilo Moana 32.2 58.4 TowCam 43.1 60.4 ABE 39.6 53.1 Tu'i Malila 43.5 56.3

126 Curtis similarity ranged from 40.1% between Alviniconcha sp. and B. brevior communities to 59.5% between I. nautilei and mixed I. nautilei/B. brevior communities

(Table 6).

Table 6: Results of ANOSIM procedure using species’ abundances among foundation fauna types averaged across all site groups. Percent similarity of species’ biomasses and species’ abundances reported between foundation fauna types (above the line) and among collections from a foundation fauna type (below the line). R Significance % Similarity Statistic Level* Alviniconcha vs Biomass Abundance Bathymodiolus 0.70 0.03 19.7 40.1 Ifremeria 0.49 0.04 33.2 50.9 Alvin/Ifrem 0.00 0.67 24.1 48.8 Bathy/Ifrem 1.00 0.06 28.1 45.0 Ifremeria vs. Bathymodiolus 0.82 0.02 33.9 48.6 Alvin/Ifrem -0.14 0.69 44.1 57.4 Bathy/Ifrem 0.31 0.06 46.6 59.5 Bathymodiolus vs Alvin/Ifrem 1.00 0.11 33.0 46.1 Bathy/Ifrem 0.43 0.15 40.8 53.7 Alvin/Ifrem vs Bathy/Ifrem 0.58 0.10 41.8 54.5 Alviniconcha 43.1 48.3 Ifremeria 48.3 61.4 Bathymodiolus 37.5 49.4 Bathy/Ifrem 46.6 61.2 Alvin/Ifrem 42.3 52.7 * Significance levels in bold are significant at P < 0.05. 127

Figure 4: Rarefaction curves showing number of species per number of individuals collected among a) sites and b) foundation fauna types.

Seven samples were collected from sulfide substrates and 6 samples were collected from lava substrates at TwoCam and Kilo Moana. While average numbers of species in the collections was significantly lower on sulfides than lavas (P = 0.03),

Pielous’s evenness index and Shannon’s diversity index were not significantly different between the two substrate types (P > 0.4). Based on ANOSIM results using associated 128 fauna abundance or biomass, there were no significant differences between substrate types (Global R > 0.083, P > 0.19).

Diversity – To compare species diversity among our quantitative collections the rarefaction method developed by Sanders (1968) was used, which allow comparisons among data sets with differences in sampling effort. TowCam and Kilo Moana are characterized by lower diversity relative to ABE and Tu’i Malila (Fig. 4a, Table 7).

Additionally, ABE has higher diversity than Tu’i Malila. Mean species richness (Table 7) of collections from Kilo Moana was significantly lower than ABE (P = 0.004) or Tu’i

Malila (P = 0.02). Towcam had a significantly lower mean Pielou’s evenness (Table 7) than Tu’i Malila (P = 0.04). Mean Shannon diversity index (Table 7) of collections from

Kilo Moana and TowCam were significantly lower than collection from ABE (P < 0.04)

Table 7: Diversity indices among site or among foundation fauna types. Significance is determined by one-way ANOVA with P < 0.05.

Mean Mean Mean No. No. Shannon Pielou's Species Samples Diversity Evenness (Pooled Total) (H') (J')

Site Kilo Moana 7 8.14 (22)a 0.52a 0.27ab Two Cam 6 10.85 (25)ab 0.45a 0.19a ABE 12 15.25 (44)b 1.05b 0.4ab Tu'i Malila 11 14.36 (36)b 1.21b 0.47b Community Type Alviniconcha 8 10.25 (26)a 1.21 0.56a Ifremeria 10 13.3 (33)ab 0.92 0.36ab Bathymodiolus 9 12.22 (37)ab 0.68 0.26ab Ifrem/Bathy 6 17.17 (36)b 0.69 0.24b Alvin/Ifrem 3 11.67 (20)ab 1.05 0.42b

129 or Tu’i Malila (P < 0.005).

In terms of foundation fauna types, collections associated with Bathymodiolus brevior and Ifremeria nautilei appear to have leveled off at similar species richness (Fig.

4b). Mixed I. nautilei/B. brevior collections have lower species richness, but also appear to have reached an asymptote (Fig. 4b). Alviniconcha sp. communities had a significantly higher mean Pielou’s evenness (Table 7) than mixed I. nautilei/B. brevior and B. brevior communities (P < 0.02). There were no differences in mean species richness or mean

Shannon diversity index (Table 7) among community types (P > 0.07).

To test whether indicators of habitat structure were predictors of the community structure indices, we determined if there were relationships between shell surface area, biomass or abundance of the foundation fauna and number of species, Shannon diversity or Pielou’s evenness in our collections. There was a weak linear relationship between shell surface area and species richness among collections (P = 0.058, R2 = 0.075), but no relationship between shell surface area and Pielou’s evenness or Shannon diversity (P >

0.3). Foundation fauna biomass in a collection was a significant predictor of species richness in a negative exponential function (R2 = 0.91, P < 0.001), but it did not predict

Shannon diversity or Pielou’s evenness (P > 0.1). Log-transformed abundances of foundation fauna had a significant linear relationship with species richness (R2 = 0.24, P

< 0.001), as well as the Shannon diversity (R2 = 0.18, P < 0.005).

Physiological condition of mussels – The residuals of the log AFDW to log volume relationship and the residuals of the arcsin-transformed tissue percent water to log volume relationship of a subset (10-15) of individuals from each mussel collection were 130 used as an indicator of physiological condition of the mussels in that collection. The residuals of the log AFDW to log volume relationship failed to fit a normal distribution

(Ryan-Joiner normality test: P < 0.01) and were analyzed using a Kruskal-Wallace equality of populations test to test for significant differences among collections or sites.

There were no significant differences in the residuals of AFDW to shell volume regression of the subsample of mussels among collections (P = 0.1) or among sites (P =

0.3). Residuals of tissue percent water to shell volume from the subsample were normally distributed (Ryan-Joiner normality test: P > 0.1) and a one-way ANOVA test was used to test significant differences among collections or sites. Overall, there were significant differences among collections and among sites (P < 0.001). In particular, mussels from subsamples at Kilo Moana were significantly lower in percent water than other sites (P <

0.001). Because differences in the tissue percent water to shell volume residuals among the sites were detected, the relationship between the median percent water of the mussel subsample several community parameters were determined. There were no significant relationships (P > 0.09) between median percent water and mean number of species,

Shannon diversity index, Pielou’s evenness index, associated fauna abundance or associated fauna biomass.

Discussion

Functional Similarity of ELSC fauna to MOR fauna – Hydrothermal vent communities at

Mid-Ocean Ridges (MORs) can be structured along abiotic gradients from higher to lower temperature, active to diffuse venting, higher to lower sulfide concentrations and lower to higher oxygen concentrations (Le Bris et al. 2006, Shank et al. 1998, Tunnicliffe 131 et al. 1997). The MORs of the Eastern Pacific Rise are characterized by alvinellid polychaetes distributed closest to high temperature vent openings, dense aggregations of siboglinid tubeworms in warm-water diffuse venting and bathymodiolin mussels and vesicomyid clams inhabiting areas of lower temperature diffuse venting (Shank et al.

1998).

At the ELSC, there is a strong correlation between the distribution of foundation fauna type and in situ measurements of temperature and sulfide and oxygen concentrations at ABE and Tu’i Malila (Podowski et al. 2009). Alviniconcha sp. and

Ifremeria nautilei are in warm-water diffuse flow and Bathymodiolus brevior inhabits areas of lower temperature diffuse venting. Similar observations have been made where these species are co-distributed at vents in the Manus Basin (Galkin 1997) and the Lau and North Fiji Basins (Desbruyères et al. 1994, 2006a; Podowski et al. 2009). This pattern corroborates laboratory experiments of thermo-chemical tolerance limits where

Alviniconcha sp. had an order of magnitude higher metabolite uptake rate than I. nautilei or B. brevior (Henry et al. 2008). This is one the highest metabolite uptake rates from a chemoautotrophic megafauna at a hydrothermal vent and suggests that Alviniconcha sp. may competitively exclude I. nautilei from areas with highest sulfide concentrations when both are present (Waite et al 2008).

The physiological ecology of the ELSC foundation fauna has similarities to some of the MOR vent chemoautotrophic fauna. Alviniconcha sp. is similar to the siboglinid polychaetes Riftia pachyptila and Tevnia jerichoana at the EPR and Ridgeia piscesae at the JFR, where each species can occupy a zone of higher temperature and higher sulfide concentrations relative to other chemoautotrophic foundation fauna at diffuse flow vents 132 (Fustec et al. 1987; Shank et al. 1998; Sarrazin et al. 2002; Le Bris et al. 2008) and have high metabolic rates (Childress et al. 1984, Girguis & Childress 2006, Henry et al. 2008,

Nyholm et al 2008), with the exception of T. jerichonana of which little is known about it’s metabolism, but has comparable in situ sulfide and oxygen uptake rates to R. pachyptila (Moore et al. 2009). Ifremeria nautilei occupies the niche with the widest variations in thermo-chemical conditions (Podowski et al. 2009). This suggests, along with low rates of autotrophy and observations of heterotrophy in the lab (Henry et al.

2008), this species is well situated for changes in hydrothermal flux on relatively small spatial and temporal scales. The thermo-chemical habitat of I. nautilei is analogous to the environment occupied by Bathymodiolus thermophilus at the EPR, which had sulfide concentrations varying from 0-325 µM, oxygen concentrations varying from 0-110 µM, and temperature ranges from 2.1-14 ºC (Fisher et al. 1988, Moore et al. 2009). The habitat of Bathymodiolus brevior at ELSC is characterized by near-ambient temperatures and lower sulfide concentrations (Podowski et al. 2009). The habitat of B. brevior is more analogous to bathymodiolin mussels on the Mid-Atlantic Ridge (MAR) than that of B. thermophilus on the EPR. Bathymodiolus puteoserpentis and B. azoricus from MAR live in environments characterized by low temperatures, low sulfide concentrations (Van

Dover 1995), and low concentrations of minerals in vent fluids (Desbruyères et al. 2000).

Additionally, similar conditions are present in the environment inhabited by senescent

Ridgeia piscesae tubeworms on the Juan de Fuca Ridge (JDF), which is characterized by low temperature (< 5 ºC), low sulfide concentrations (< 10 µM), and low flow intensity

(Sarrazin et al. 1999). ). It was proposed that B. brevior at the ELSC may oxidize thiosulfate in significant quantities since environmental abundances were high (up to 85 133 µM), specifically in patches inhabited by the mussels (Mullaugh et al. 2008, Waite et al.

2008). Thiosulfate production at one vent locality at Kilo Moana from ELSC was negatively correlated with temperature (Waite et al. 2008). Bathymodiolus brevior may be limited to low temperature and low sulfide environments because their endosymbionts are reliant on thiosulfate for their energy needs.

In general, the snail beds are physically comparable to mussel beds. A significant difference among the impacts of the snails and mussels on their associated fauna may be driven by differences in the impacts of filtering water and grazing by the three species, although this is not well constrained. Barnacles (mostly Eochionelasmus ohtai and

Vulcanolepas sp.) constitute another form of biogenic substrata that share many physical characteristics with the chemoautotrophic snails and mussels, yet live in areas at near ambient deep-sea thermo-chemical conditions (Podowski et al. 2009) and lack endosymbiotic chemoautotrophic bacteria (but Vulcanolepas spp. has epibiotic chemoautrophic bacteria on elongated cirral setae, see Southward & Newman 1998 and

Suzuki et al. 2009). The majority of the ELSC biogenic substrata (i.e. snails, mussels and barnacles) are composed of calcium carbonate shells, are low-lying to the hard substrata, are horizontally spreading, and, excluding the barnacles, contain layers one to several individuals thick forming an interstitial matrix. Larger tubeworms (Arcovestia ivanovi and Lamellibrachia columna) were observed infrequently and dense aggregations of a very small tubeworm in the genus Oasisia were distributed in a relatively small area (~10 cm2) near an active orifice at TowCam. Tubeworms have chitinous tubes and typically extend out into the water column, but the Oasisia tubeworms were growing horizontally along the substratum. 134

Along-axis gradients at ELSC – Mean biomass and abundance of the four sites were not significantly different along the ridge axis, while there were significant trends in community structure and species composition. Because of the brittle nature of the andesitic rocks, sampling was more often successful at Tu’i Malila and ABE. The seafloor at Kilo Moana and TowCam tended to be more difficult to sample with the mussel/snail pot. Animals tended to be located in fissures and cracks of the basaltic substratum resulting in problems that led to lower sample yields at basaltic substrata.

Though sampling was more intensive at the two southern sites, significant differences in univariate measures of community structure exist between northern and southern sites. Mean Shannon diversity index, mean number of species, and mean

Pielou’s evenness index generally increased southward (Table 7). Though the rarefaction curve for ABE was higher than the more southern site of Tu’i Malila (Fig. 4a), univariate measures of community structure were not significantly different between the two sites

(Table 7). It is tempting to correlate these community patterns with along-axis changes in ridge topology and vent fluid chemistry (see Introduction), but caution must be taken in interpreting fine-scale ecology patterns from large-scale geological phenomena. It is unclear which of these variables are important to fauna. Differences in community structure along the ridge axis can also be attributed to differences in the mean abundance of the numerically dominant associated fauna. For many species, mean abundance was higher at the southern sites (Table 2). Only the mean abundances of Archinome rosacea aff. and Olgasolaris tollmanni were higher at the northern sites (Table 2).

135 Fine-scale structure of foundation fauna communities – While the distributions of individual species vary along the ELSC ridge axis, communities are further structured within a particular site by foundation fauna type (Fig. 5). Fine scale community structure may result from microhabitat variations (Bergquist et al. 2004, 2005; Govenar et al.

2005), biological characteristics of the foundation species (Cordes et al. 2005, Govenar &

Fisher 2007; Van Dover 2003), or the synergistic interaction between biological characteristics and environment (Bergquist et al. 2003; Le Bris et al. 2006). Thermo- chemical characteristics are closely correlated to the distributions of the foundation

Figure 5: Non-metric multidimensional scaling plot showing the similarity of composition among samples of communities associated with Alviniconcha sp., Ifremeria nautilei, and

Bathymodiolus brevior. Distance between samples is based on Bray-Curtis similarity coefficients. Shapes designate foundation fauna type and shading represents sites. 136 species (Podowski et al. 2009). It is unclear from our data whether species found at a low temperature, low sulfide environment is thermo-chemically excluded from an

Alviniconcha sp. habitat, or whether those species are excluded because of competition, predation (Micheli et al. 1999), or preferred prey availability.

Mixed Ifremeria nautilei/Alviniconcha sp. communities had, in general, a higher total number of species and had significantly higher mean numbers of species in a collection, significantly lower Pielou’s evenness (Table 7), and significantly higher mean associated fauna abundance (Table 1) than Alviniconcha sp. communities, yet had nearly the lowest Shannon diversity index. This suggests these organisms or the microhabitat they live in facilitate one or two associated species that dominate their species lists and skew the evenness of these habitats. Communities associated with only I. nautilei and only Bathymodiolus brevior had similar compositions. Though they are morphological very different, their shells are smooth and could facilitate colonization of fouling fauna such as barnacles and limpets.

Occurrence of several species was strongly correlated with particular foundation fauna (Tables 2, 4). In general, limpets were not a large component of Alviniconcha sp. communities, which was dominated by Austinograea spp. and Chorocaris vandoverae.

The spiny periostracum of Alviniconcha sp. snails may impede colonization by some fouling fauna such as gastropods and barnacles. The relatively low abundance of limpet species in Alviniconcha sp. beds may explain the higher Pielou’s evenness index and

Shannon diversity index despite the lower mean number of species in a collection (Table

7). The high abundance of the copepod Stygiopontius spp. in Alviniconcha sp. communities suggests it prefers this habitat and may seek refuge where it is small enough 137 to navigate through the spiny matrix. Alvinellid polychaetes, Hesiospina sp. (polychaete),

Thermopolynoe branchiata (polynoid polychaete) and Stygiopontius sp. (copepod), were also most abundant in communities where Alviniconcha sp. made up greater than 25% of foundation fauna abundance or biomass. The high mean abundance of Lepetodrilus schrolli in mixed Ifremeria nautilei/Alviniconcha sp. communities lowered Pielou’s evenness index and the Shannon diversity index of the community.

Mussel tissue mass and water content can vary within the confines of the shell and is known to fluctuate with habitat quality at chemosynthetic-based ecosystems (Smith

1985, Fisher et al. 1988, Nix et al. 1995, Bergquist et al. 2004, Dattagupta et al. 2004).

All the sites we sampled from were active and, in general, had high standing stock biomass. Mussels subsampled from 2005 collections at Kilo Moana had significantly lower water content than the other three sites, hinting that they were in “better” condition.

It is unclear why mussels would be in better physiological at Kilo Moana because, qualitatively, nothing stands out from here indicating it is a healthier site than the other 3 study sites. Furthermore, we did not see mussels infected with an epizootic fungus, as documented in the neighboring North Fiji Basin (Van Dover et al. 2007).

Conclusions – Our study represents the most intense quantitative ecological sampling regime reported from a back-arc basin. We were able to demonstrate variation in community composition at geographic scales within the ELSC and fine-scale variation in community composition among habitat types defined by their foundation species, regardless of location within the ridge-axis. The presence and persistence of these communities would likely not be possible without the facilitation of Alviniconcha sp., 138 Ifremeria nautilei, or Bathymodiolus brevior. By providing physical structure or heterogeneity, contributing to primary production of nutrients or ameliorating the thermo- chemical environment of the ELSC, these foundation species facilitate species occurrence and ensure the persistence of distinct communities. The impact of foundation species in structuring communities appears to be greater than the role of site-specific geologic variables. This is evidenced by significant differences in the ANOSIM analyses by foundation species type (Table 6) and no significant differences among sites (Table 5).

Microhabitat variations have been identified as a key structuring force sites at the EPR

(Fustec et al. 1987, Fisher et al. 1988, Van Dover 2002, Govenar et al. 2005, Le Bris et al. 2006, Gollner et al. 2007, Lutz et al. 2008, Matabos et al. 2008), the Juan de Fuca and

Gorda Ridges (Bates et al. 2005, Kelly et al. 2007, Marcus et al. 2009), the mid-Okinawa

Trough (Hashimoto et al. 1995), and the mid-Atlantic Ridge (Desbruyères et al. 2000). At back-arc basins it is still unclear how the differences in geology and tectonic setting influence communities and whether they affect the communities to the same degree as at

MORs. Future studies at the ELSC should focus on in situ analysis of the thermo- chemical environment and its temporal variation in conjunction with quantitative whole community collections, such that each collection has a discrete environmental characterization to tease apart the relationship between abiotic factors, habitat quality and faunal distributions.

Acknowledgments – This work would not be possible without the skill and dedication of the captains and crews of the R/V Melville and the crew of the ROV JASON II during the 2005 (TUIM07MV) and 2006 (MGLN07MV) cruises. We thank D. Desbruyères, S. 139 Hourdez, G. Telesnicki, E. Podowski, E. Becker, S. Nonu and J. DeMazieres for extensive assistance at sea. This manuscript has benefited greatly from discussions and editorial assistance from S. Schaeffer and J. Stauffer. We thank the Kingdom of Tonga for permitting collection in their waters. The map in Fig. 1 was prepared with assistance from E. Podowski. This work was funded by NSF Grant OCE 003403953 to CRF and support of KAZ by the Pennsylvania State University.

Notes – Planned coauthors for a paper resulting from this chapter include Dr. Charles R.

Fisher, Lara Miles and Molly Steele. LM and MS carried out condition index experiments and abundance and biomass measurements and enumerations. CRF contributed to the study design, data interpretation and preparation of the manuscript.

Literature Cited

Bates AE, Tunniciffe V, Lee RW (2005) Role of thermal conditions in habitat selection

by hydrothermal vent gastropods. Marine Ecology Progress Series 305:1-15

Bergquist, DC, Ward T, Cordes EE, McNelis T, Howlett S, Kosoff R, Hourdez S, Carney

R,Fisher CR (2003) Community structure of vestimentiferan-generated habitat islands

from Gulf of Mexico cold seeps. Journal of Experimental Marine Biology & Ecology

289:197-222

Bergquist DC, Fleckenstein C, Szalai EB, Knisel J, Fisher CR (2004) Environment drives

physiological variability in the cold seep mussel Bathymodiolus childressi. Limnology

and Oceanography 49:706-715

Bergquist, D. C., C. Fleckenstein, J. Knisel, B. Begley, I. R. MacDonald, and C. R. Fisher 140 (2005), Variations in seep mussel bed communities along physical and chemical

environmental gradients. Marine Ecology Progress Series 293:99-108

Bird P (2003) An updated digital model of plate boundaries. Geochem. Geophys. Geosyst. 4(3),

1027 doi:10.1029/2001GC000252

Both R, Crook K, Taylor B, Brogan S, Chappell B, Frankel E, Liu L, Sinton J, Tiffin D (1986)

Hydrothermal chimneys and associated fauna in the Manus back-arc basin, Papua New

Guinea. Eos 67: 489-490

Bruno JF, Bertness MD (2001) Habitat modification and facilitation in benthic marine

communities. In Bertness MD, Gaines SD, Hay ME (eds) Marine Community Ecology.

Sinauer Associates, Inc., Sunderland, MA, p 201-218

Bruno JF, Stachowicz JJ, Bertness MD (2003) Inclusion of facilitation into ecological theory.

Trends in Evolution and Ecology 18:119-125

Carney RS (1994) Consideration of the oasis analogy for chemosynthetic communities at Gulf of

Mexico hydrocarbon vents. Geo-Marine Letters 14:149-159

Childress JJ, Mickel TJ (1980) A motion compensated shipboard precision balance

system. Deep Sea Research Part A Oceanographic Research Papers 27:965-970

Childress JJ, Arp AJ & Fisher CR (1984) Metabolic and blood characteristics of the

hydrothermal vent tube-worm Riftia pachyptila. Marine Biology 83:109-124

Clarke KR, Warwick RM (2001) Change in Marine Communities: An Approach to

Statistical Analysis and Interpretation, Vol. Primer-E, Ltd., Plymouth, UK

Colwell RR (2006) EstimateS: Statistical estimation of species richness and shared

species from samples.Version 8. Persistent URL < purl.oclc.org/estimates> 141 Cordes EE, Hourdez S, Predmore BL, Redding ML, Fisher CR (2005) Succession of

hydrocarbon seep communities associated with the long-lived foundation species

Lamellibrachia luymesi. Marine Ecology Progress Series 305:17-29

Crosby MP, Gale LD (1990) A review and evaluation of bivalve condition index

methodologies with a suggested standard method. Journal of Shellfish Research

9:233-237

Dattagupta S, Bergquist D, Szalai E, Macko S, Fisher C (2004) Tissue carbon, nitrogen,

and sulfur stable isotope turnover in transplanted Bathymodiolus childressi

mussels: relation to growth and physiological condition. Limnology and

Oceanography 49:1144-1151

Dayton P (1972) Toward an understanding of community resilience and the potential

effects of enrichments to the benthos at McMurdo Sound. In: Baker BC (ed)

Proceedings of the Colloquium on Conservation Problems in Antarctica. Allen

Press, Lawrence, Kansas, p 81-96

Desbruyères D, Almeida A, Biscoito M, Comtet T, Khripounoff A, Bris NL, Sarradin

PM, Segonzac M (2000) A review of the distribution of hydrothermal vent

communities along the northern Mid-Atlantic Ridge: dispersal vs. environmental

controls. Hydrobiologia 440:201-216

Desbruyères D, Alayse-Danet A-M, Ohta S, Scientific Parties of BIOLAU and STARMER

cruises (1994) Deep-sea hydrothermal communities in Southwestern Pacific back-arc

basins (the North Fiji and Lau Basins): composition, microdistribution and food web.

Marine Geology 116:227-242 142 Desbruyères D, Hashimoto J, Fabri M-C (2006a) Composition and biogeography of

hydrothermal vent communities in Western Pacific Back-Arc Basins. In: Christie DM,

Fisher CR, Lee S-M, Givens S (eds) Back-Arc Spreading Systems: Geological,

Biological, Chemical, and Physical Interactions. American Geophysical Union,

Washington D.C., p 215-234

Ferrini VL, Tivey MK, Carbotte SM, Martinez F, Roman C (2008) Variable morphologic

expression of volcanic, tectonic, and hydrothermal processes at six hydrothermal vent

fields in the Lau back-arc basin. Geochemistry Geophysics Geosystems 9:33 pp.

Fisher CR, Childress JJ, Arp AJ, Brooks JM, Distel DL, Favuzzi JA, Felbeck H, Hessler

RR, Johnson KS, Kennicutt II MC, Macko SA, Newton A, Powell MA, Somero

GN, Soto T (1988) Microhabitat variation in the hydrothermal vent mussel,

Bathymodiolus thermophilus, at the Rose Garden vent on the Galapagos Rift.

Deep-Sea Research 35: 1769-1791

Fisher CR (1996) Ecophysiology of primary production at deep-sea vents and seeps. In:

Uiblein F, Ott J, Stachowtish M (eds) Deep-sea and extreme shallow-water

habitats: affinities and adaptations. Biosystematics and Ecology Series 11: 313-

336

Fustec A, Desbruyères D, Juniper SK (1987) Deep-sea hydrothermal vent communities at 13°N

on the East Pacific Rise: microdistribution and temporal variation. Biological

Oceanography 4: 121-164

Galkin SV (1997) Megafauna associated with hydrothermal vents in the Manus Back-Arc Basin

(Bismarck Sea). Marine Geology 142: 197-206 143 Girguis P, Childress JJ (2006) Metabolite uptake, stoichiometry and chemoautotrophic function

of the hydrothermal vent tubeworm Riftia pachyptila: responses to environmental

variations in substrate concentrations and temperature. Journal of Experimental Biology

209: 3516-3528

Gollner S, Zekely J, Govenar B, Le Bris N, Nemeschkal HL, Fisher CR, Bright M (2007)

Tubeworm-associated permanent meiobenthic communities from two chemically

different hydrothermal vent sites on the East Pacific Rise. Marine Ecology Progress

Series 337: 39-49

Govenar B, Fisher CR (2007) Experimental evidence of habitat provision by aggregations of

Riftia pachyptila at hydrothermal vents on the East Pacific Rise Marine Ecology 28(1):3-

14

Govenar B, Le Bris N, Gollner S, Glanville J, Aperghis AB, Hourdez S, Fisher CR (2005)

Epifaunal community structure associated with Rifta pachyptila aggregations in

chemically different hydrothermal vent habitats. Marine Ecology Progress Series 305:67-

77

Hashimoto J, Ohta S, Fujikura K, Miura T (1995) Microdistribution pattern and biogeography of

the hydrothermal vent communities of the Minami-Ensei Knoll in the mid-Okinawa

trough, Western Pacific. Deep Sea Research Part I: Oceanographic Research Papers

42:577-598

Henry MS, Childress JJ, Figueroa D (2008) Metabolic rates and thermal tolerances of

chemoautotrophic symbioses from Lau Basin hydrothermal vents and their implications

for species distributions. Deep Sea Research Part I: Oceanographic Research Papers

55:679-695 144 Hessler RR, Lonsdale PF (1991) Biogeography of Mariana Trough hydrothermal vent

communities. Deep Sea Research Part A Oceanographic Research Papers 38:185-199

Jakob EM, Marshall SD, Uetz GW (1996) Estimating fitness: a comparison of body

condition indices. Oikos 77:61-67

Johnson KS, Beehler CL, Sakamoto-Arnold CM, Childress JJ (1986) In situ

measurements of chemical distributions in a deep-sea hydrothermal vent field.

Science 231: 1139-1141

Johnson KS, Childress JJ, Hessler RR, Sakamoto-Arnold CM, Beehler CL (1988) Chemical and

biological interactions in the Rose Garden hydrothermal vent field, Galapagos spreading

center. Deep Sea Research Part A. Oceanographic Research Papers 35:1723-1744

Johnson KS, Childress JJ, Beehler CL, Sakamoto CM (1994) Biogeochemistry of hydrothermal

vent mussel communities: the deep-sea analogue to the intertidal zone. Deep-Sea

Research I 41:993-1011

Kelly N, Metaxas A, Butterfield D (2007) Spatial and temporal patterns of colonization by deep-

sea hydrothermal vent invertebrates on the Juan de Fuca Ridge, NE Pacific. Aquatic

Biology 1:1-16

Le Bris N, Govenar B, Le Gall C, Fisher CR (2006) Variability of physico-chemical conditions

in 9°50'N EPR diffuse flow vent habitats. Marine Chemistry 98:167-182

Lutz RA, Shank TM, Luther GW, Vetriani C, Tolstoy M, Nuzzio DB, Moore TS, Waldhauser F,

Crespo-Medina M, Chatziefthimiou AD, Annis ER, Reed AJ (2008) Interrelationships

Between Vent Fluid Chemistry, Temperature, Seismic Activity, and Biological

Community Structure at a Mussel-Dominated, Deep-Sea Hydrothermal Vent Along the

East Pacific Rise. Journal of Shellfish Research 27:177-190 145 Marcus J, Tunnicliffe V, Butterfield DA (2009) Post-eruption succession of macrofaunal

communities at diffuse flow hydrothermal vents on Axial Volcano, Juan de Fuca Ridge,

northeast Pacific. Deep Sea Research Part II: Topical Studies in Oceanography In Press:

doi:10.1016/j.dsr2.2009.05.004

Martinez F, Taylor B (2003) Controls on back-arc crustal accretion: insights from the Lau,

Manus and Mariana basins. Geological Society, London, Special Publications 219:19-54

Martinez F, Taylor B, Baker ET, Resing JA, Walker SL (2006) Opposing trends in crustal

thickness and spreading rate along the back-arc Eastern Lau Spreading Center:

Implications for controls on ridge morphology, faulting, and hydrothermal activity. Earth

and Planetary Science Letters 245(3-4):655-672

Matabos M, Le Bris N, Pendlebury S, Thiébaut E (2008) Role of Physico-Chemical Environment

on Gastropod Assemblages at Hydrothermal Vents on the East Pacific Rise (13°N/EPR).

Journal of the Marine Biological Association of the United Kingdom 88:995-1008.

Micheli F, Peterson CH, Mullineaux LS, Fisher CR, Mills SW, Sancho G, Johnson GA, Lenihan

HS (2002) Predation structures communities at deep-sea hydrothermal vents. Ecological

Monographs 72: 365-382

Miura T, Hashimoto J (1991) Two new branchiate scale-worms (Polynoidae: Polychaeta) from

the hydrothermal vent of the Okinawa trough and the volcanic seamount off Chichijima

island. Proceedings of the Biological Society of Washington 104:166-174

Moore TS, Shank TM, Nuzzio DB, Luther III GW (2009) Time-series chemical and temperature

habitat characterization of diffuse flow hydrothermal sites at 9°50'n east pacific rise.

Deep Sea Research Part II: Topical Studies in Oceanography In Press:

doi:10.1016/j.dsr2.2009.05.008 146 Mullaugh K, Luther III GW, Ma S, Moore TS, Yucel M, Becker EL, Podowski EL, Fisher CR,

Trouwborst RE, Pierson BK (2008) Voltammetric (Micro)Electrodes for the In Situ

2+ Study of Fe Oxidation Kinetics in Hot Springs and S2O Production at Hydrothermal

Vents. Electroanalysis 20:280-290

Nix E, Fisher C, Vodenichar J, Scott K (1995) Physiological ecology of a mussel with

methanotrophic endosymbionts at three hydrocarbon seep sites in the Gulf of Mexico.

Marine Biology 122:605-617

Nyholm SV, Robidart J, Girguis PR (2008) Coupling Metabolite Flux to Transcriptomics:

Insights Into the Molecular Mechanisms Underlying Primary Productivity by the

Hydrothermal Vent Tubeworm Ridgeia piscesae. Biol Bull 214:255-265

Ohta S (1990) Deep-sea submersible survey of the hydrothermal vent community on the

northeastern slope of the Iheya Ridge, the Okinawa Trough. JAMSTEC Journal of

Deep Sea Research 6:145-156

Podowski EL, Moore TS, Zelnio KA, Luther III GW, Fisher CR (2009) GIS-based analysis of

realized distributional patterns of diffuse flow mega-fauna on the Eastern-Lau Spreading

Center, Tonga. Deep Sea Research Part I: Oceanographic Research Paper In Press:

doi:10.1016/j.dsr.2009.07.002

Sanders HL (1968) Marine benthic diversity: a comparitive study. American Naturalist

102:243-282

Sarrazin J, Juniper SK, Massoth GJ, Legendre P (1999) Physical and chemical factors

influencing species distributions on hydrothermal sulfide edifices of the Juan de

Fuca Ridge, northeast Pacific. Marine Ecology Progress Series 190:89-112 147 Sarrazin J, Levesque C, Juniper SK, Tivey MK (2002) Mosaic community dynamics on the Juan

de Fuca Ridge sulphide edifices: substratum, temperature and implications for trophic

structure. Cahiers Biologie Marine 43:275-279

Shank TM, Fornari DJ, Von Damm KL, Lilley MD, Haymon RM, Lutz RA (1998) Temporal

and spatial patterns of biological community development at nascent deep-sea

hydrothermal vents (9˚50' N, East Pacific Rise). Deep-Sea Research II 45:465-515

Smith KL (1985) Deep-sea hydrothermal vent mussels: nutritional state and distribution

at the Galapagos Rift. Ecology 66:1067-1080

Southward AJ, Newman WA (1998) Ectosymbiosis between filamentous sulphur bacteria

and a stalked barnacle (Scalpellomorpha, Neolepadinae) from the Lau back-arc

basin, Tonga. Cahiers Biologie Marine 39:259-262

Suzuki Y, Suzuki M, Tsuchida S, Takai K, Horikoshi K, Southward AJ, Newman WA,

Yamaguchi T (2009) Molecular Investigations of the Stalked Barnacle

Vulcanolepas Osheai and the Epibiotic Bacteria from the Brothers Caldera,

Kermadec Arc, New Zealand. Journal of the Marine Biological Association of the

UK 89:727-733

Tsurumi M, Tunnicliffe V (2003) Tubeworm-associated communities at hydrothermal

vents on the Juan de Fuca Ridge, northeast Pacific. Deep-Sea Research I 50: 611-

629

Tunnicliffe V, Embley RW, Holden JF, Butterfield DA, Massoth GJ, Juniper SK (1997)

Biological colonization of new hydrothermal vents following an eruption on Juan de Fuca

Ridge. Deep Sea Research Part I: Oceanographic Research Papers 44:1627-1644 148 Tyler PA, German CR, Ramirez-Llodra E, Van Dover CL (2003) Understanding the

biogeography of chemosynthetic ecosystems. Oceanologica Acta 25:227-241

Van Dover CL (1995) Ecology of Mid-Atlantic Ridge hydrothermal vents. In: Hydrothermal

Vents and Processes. Geological Society Special Publication, No. 87, pp 257-294

Van Dover CL (2002) Community structure of mussel beds at deep-sea hydrothermal

vents. Marine Ecology Progress Series 230:137-158

Van Dover CL (2003) Variation in community structure within hydrothermal vent mussel

beds of the East Pacific Rise. Marine Ecology Progress Series 253:55-66

Van Dover CL, Ward ME, Scott JL, Underdown J, Anderson B, Gustafson C, Whalen M,

Carnegie RB (2007) A fungal epizootic in mussels at a deep-sea hydrothermal

vent. Marine Ecology 28:54-62

Waite TJ, Moore TM, Childress JJ, Hsu-Kim H, Mullaugh KM, Nuzzio DB, Paschal AN,

Tsang J, Fisher CR, Luther GW (2008) Variation in Sulfur Speciation with

Shellfish Presence at a Lau Basin Diffuse Flow Vent Site. Journal of Shellfish

Research 27(1):163-168

Zellmer K, Taylor, B (2001) A three-plate kinematic model for Lau Basin opening.

Geochemistry Geophysics Geosystems 2:1-26

149 CHAPTER 4

Biogeography of the Eastern-Lau Spreading Center Fauna

To understand the origin and biogeography of the ELSC communities, the fauna need to be placed in the context of other hydrothermal systems at back-arc basins and

MORs. Though our sampling was more intensive and uncovered additional species not considered by Desbruyères et al. (2006a), the pattern of similarity among genera remained similar. The similarity among the genera present at western Pacific back-arc basins is negatively correlated with distance, consistent with Desbruyères et al. (2006a).

Seventy-eight genera have been documented from the ELSC, which shares the most generic similarity to the North Fiji Basin and Manus Basin fauna (Fig. 1). Additionally, several genera reported from the ELSC have thus far only been reported from the western

Pacific back-arc basin biogeographic province (Appendix 1): Mollusca: Heliocrenon,

Ifremeria (=Olgaconcha), Olgasolaris, Symmetromphalus, Ventsia; Polychaeta:

Arcovestia, Thermopolynoe, Thraumastros; Arthropoda: Imbricaverruca, Nautilocaris,

Neobrachylepas; Chordata: Thermobiotes.

My analysis corroborates that of Desbruyères et al (2006a) in determining that the generic composition of western Pacific back-arc basin hydrothermal vent communities is more similar to the MAR than the eastern Pacific vent sites. The western Pacific was connected to the East Pacific Rise through the now extinct Kula Ridge 43 mya (Hessler

& Lonsdale 1991), providing a potential historical conduit for vent taxa across the Pacific

Ocean. Bachraty et al.’s (2009) biogeographic models suggest the East Pacific Rise as the center for dispersal of the hydrothermal vent fauna. Hessler and Lonsdale (1991) reported 150 several species and genera at the Marianas Trough that were similar to taxa found at vents on the Juan de Fuca Ridge, East Pacific Rise and Galápagos Ridge. One third of the genera reported from our ELSC collections (15 out of 46 genera) are reported from only the eastern and western Pacific (Appendix 1). Because I only collected from communities associated with chemoautotrophic foundation species, and not peripheral fauna, this is likely an underestimate of the shared genera between eastern and western Pacific vent communities. Because the eastern Pacific vents were the focus of an intensive sampling effort spread out over several decades, the fauna are much better characterized than the western Pacific vents. The larger biogeographic picture may be distorted by focused sampling at few locations and sparser, less quantitative sampling at several other locations.

Though the CIR fauna are not as well studied as the Pacific and North Atlantic fauna, examination of my collections revealed five genera reported only from the CIR or western Pacific back-arc basin vents (Appendix 1). In their initial survey of the CIR vents, Van Dover et al. (2001) found species that were very similar to that reported from western Pacific back-arc basins. The Indian and Pacific oceans were once connected by the Coral Sea Ridge 55 mya (Hessler & Lonsdale 1991), which may have provided another historical species conduit to the western Pacific back-arc basins. Desbruyères et al (2006a) found that the generic composition of vents at CIR and Mariana shared the most similarity with each other. In my analysis, the compositions of vents at Mariana and

NW Pacific have greater generic similarity. Nine genera in total from our ELSC collections are shared with vents on the CIR (Appendix 1). It is worth cautioning against 151 extrapolating large-scale biogeographic patterns until the fauna of the CIR, Pacific-

Antarctic Ridge and the New Zealand vents are studied in greater detail.

Figure 1: Dendrogram based on hierarchical clustering (group-average linking) of 78 genera that occur at ELSC and other hydrothermal vent sites around the world oceans. Similarity is based on Bray-Curtis coefficients. Abbreviations are the same as in Appendix 1.

Prior to this the work published in this thesis, little was known about the structure of diffuse flow communities of hydrothermal vents at a back-arc basin. Previous work was done on haphazardly collected samples (i.e. Both et al. 1986, Ohta 1990, Hessler &

Lonsdale 1991, Desbruyères et al. 1994, Galkin 1997), where much knowledge can be 152 gained about diversity and species occurrence, but less knowledge can be gained about ecological patterns or processes. Our quantitative sampling regime, while incomplete in some respects, contributes to understanding how communities are distributed along the ridge axis at a back-arc basin spreading center and uncovers important patterns of communities among very different foundation species within well-defined, but overlapping microhabitats. I acknowledge that this research can certainly be improved upon, both in design and interpretation, and the lack of chemical data with each collection weakens the interpreations of my study.

What this thesis does not address is the different roles of abiotic and ecological parameters (i.e. competition, predation and food availability) and the successional mechanisms of ELSC communities. For instance, at the East Pacific Rise, it was documented that bathymodiolin mussels were a later successional stage of the hydrothermal vent community (Fustec et al. 1987, Shank et al. 1998, Govenar et al.

2005). The near ambient conditions reported in situ (Waite et al. 2008, Podowski et al.

2009) and the lower thermo-chemical tolerance limits in laboratory experiments (Henry et al. 2008) suggest that formation of Bathymodiolus brevior communities at the ELSC could also occur at a later successional stage. Does Ifremeria nautilei arrive first to vent to get displaced to the periphery by Alviniconcha sp.? At the EPR, the tubeworm Tevnia jerichoana colonizes a new vent first, to be displaced later by Riftia pachyptila (Shank et al. 1998). Or does Alviniconcha arrive first to a new vent, followed by I. nautilei and subsequently followed by B. brevior?

The contribution this thesis does make is in laying the foundation for further community ecology studies at ELSC and generates a dataset for this region that can be 153 comparable across other back-arc basin and MOR active vent communities. The description of new species at ELSC also contributes to the growing literature of a group of important shrimp endemic to deep sea chemosynthetic-based ecosystems (Chapter 1).

Furthermore, anemones have been an often-neglected group at vents. They have a difficult taxonomic history and their soft bodies are not always amenable to some of the collection methods historically used in vent studies. There is cladistic evidence for a clade of anemones from chemosynthetic-based ecosystems (Rodríguez et al. 2009). All vent, seep and whale-fall anemones described, not including those reported in Zelnio et al. (in press; Chapter 2) shared the presence of distal cinclides on the column, thick column mesoglea, the same or more number of distal to proximal mesenteries, a fertile third mesentery cycle, presence of a sphincter forming a marginal ring, and the presence of microbasic p-mastigophores in the tentacles, in addition to their presence at chemosynthetic habitats. The expansion of the previously monotypic vent genera

Cyanothea and Alvinactis from the EPR and Juan de Fuca, respectively, across the

Pacific Ocean has important biogeographic implications that may further contribute to the understanding of the origin, speciation and radiation of vent fauna globally. The anemone fauna described in this thesis (Chapter 2) contribute to an abundant and unique community peripheral to the ELSC vents, which deserves further study at the physiological, molecular and whole community levels.

154 Literature Cited

Bachraty C, Legendre P, Desbruyères D (2009) Biogeographic relationships among deep-

sea hydrothermal vent faunas at global scale. Deep–Sea Research I, In Press:

doi:10.1016/j.dsr.2009.01.009

Both R, Crook K, Taylor B, Brogan S, Chappell B, Frankel E, Liu L, Sinton J, Tiffin D

(1986) Hydrothermal chimneys and associated fauna in the Manus back-arc basin,

Papua New Guinea. Eos 67: 489-490

Clark M, O'Shea S (2001) Hydrothermal vent and seamount fauna from the southern

Kermadec Ridge. InterRidge News 10: 14-17

Desbruyères D, Alayse-Danet A-M, Ohta S, Scientific Parties of BIOLAU and STARMER

cruises (1994) Deep-sea hydrothermal communities in Southwestern Pacific back-arc

basins (the North Fiji and Lau Basins): composition, microdistribution and food web.

Marine Geology 116:227-242

Desbruyères D, Hashimoto J, Fabri M-C (2006a) Composition and biogeography of

hydrothermal vent communities in Western Pacific Back-Arc Basins. In: Christie DM,

Fisher CR, Lee S-M, Givens S (eds) Back-Arc Spreading Systems: Geological,

Biological, Chemical, and Physical Interactions. American Geophysical Union,

Washington D.C., p 215-234

Desbruyères D, Segonzac M, Bright M (2006b) Handbook of Deep-Sea Hydrothermal Vent

Fauna (2nd ed.). Denisia, 18: 544 pp

Fustec A, Desbruyères D, Juniper SK (1987) Deep-sea hydrothermal vent communities at 13°N

on the East Pacific Rise: microdistribution and temporal variation. Biological

Oceanography 4:121-164 155 Galkin SV (1997) Megafauna associated with hydrothermal vents in the Manus Back-Arc Basin

(Bismarck Sea). Marine Geology 142: 197-206

Govenar B, Le Bris N, Gollner S, Glanville J, Aperghis AB, Hourdez S, Fisher CR (2005)

Epifaunal community structure associated with Rifta pachyptila aggregations in

chemically different hydrothermal vent habitats. Marine Ecology Progress Series 305:67-

77

Hasegawa K, Fujikura K, Okutani T (1997) Gastropod fauna associated with hydrothermal vents

in the Mariana Back-Arc Basin: summary of the results of 1996 "Shinkai 6500" dives.

JAMSTEC Journal of Deep Sea Research 13:69-83

Henry MS, Childress JJ, Figueroa D (2008) Metabolic rates and thermal tolerances of

chemoautotrophic symbioses from Lau Basin hydrothermal vents and their implications

for species distributions. Deep Sea Research Part I: Oceanographic Research Papers

55:679-695

Hessler RR, Lonsdale PF (1991) Biogeography of Mariana Trough hydrothermal vent

communities. Deep Sea Research Part A Oceanographic Research Papers 38:185-199

Lörz A, Glenner H, Lützen J (2008) New records of Rhizocephala (Cirripedia) from New

Zealand, including the first rhizocephalan records from hot vents and cold seeps.

Crustaceana 81:1013-1019

Ohta S, Kim D (2001) Submersible observations of the hydrothermal vent communities on the

Iheya Ridge, Mid Okinawa Trough, Japan. Journal of Oceanography 57:663-677

Podowski EL, Moore TS, Zelnio KA, Luther III GW, Fisher CR. (2009) GIS-based analysis of

realized distributional patterns of diffuse flow mega-fauna on the Eastern-Lau Spreading 156 Center, Tonga. Deep Sea Research Part I: Oceanographic Research Paper In Press:

doi:10.1016/j.dsr.2009.07.002

Ramirez-Llodra E, Freitga K, Blanco M, Baker C (2005) ChEssBase: an online information

system on biodiversity and biogeography of deep-sea chemosynthetic ecosystems.

University of Southampton, Southampton Oceanography Centre, School of Ocean and

Earth Science; World Wide Web electronic publications, Southampton, UK, Version 2,

SQL-server. Retrieved 12/2008 from http://www.iobis.com

Rodríguez E, Castorani C, Daly M (2008) Morphological phylogeny of the family Actinostolidae

(Anthozoa : Actiniaria) with description of a new genus and species of hydrothermal vent

sea anemone redefining the family Actinoscyphiidae. Invertebrate Systematics 22:439-

452

Shank TM, Fornari DJ, Von Damm KL, Lilley MD, Haymon RM, Lutz RA (1998) Temporal

and spatial patterns of biological community development at nascent deep-sea

hydrothermal vents (9˚50' N, East Pacific Rise). Deep-Sea Research II 45:465-515

Stecher J, Türkay M, Borowski C (2002) Faunal assemblages on the Pacific-Antarctic

Ridge near the Foundation Seamount Chain (37° 30' S, 100° 30' W). Cahiers

Biologie Marine 43:271-274

Van Dover CL, Humphris SE, Fornari D, Cavanaugh CM, Collier R, Goffredi SK, Hashimoto J,

Lilley MD, Reysenbach AL, Shank TM, Von Damm KL, Banta A, Gallant RM, Götz D,

Green D, Hall J, Harmer TL, Hurtado LA, Johnson P, McKiness ZP, Meredith C, Olson

E, Pan IL, Turnipseed M, Won Y, Young III CR, Vrijenhoek RC (2001) Biogeography

and ecological setting of Indian Ocean hydrothermal vents. Science 294: 818-823 157 Waite TJ, Moore TM, Childress JJ, Hsu-Kim H, Mullaugh KM, Nuzzio DB, Paschal AN,

Tsang J, Fisher CR, Luther GW (2008) Variation in Sulfur Speciation with

Shellfish Presence at a Lau Basin Diffuse Flow Vent Site. Journal of Shellfish

Research 27(1): 163-168

Zelnio KA, Hourdez S (2009) A new species of Alvinocaris (Crustacea: Decapoda:

Alvinocarididae) from hydrothermal vents at the East-Lau Spreading Center,

Western Pacific. Proceedings of the Biological Society of Washington 122(1): 52-

71

Zelnio KA, Rodriguez E, Daly M. Hexacorals (Anthozoa: Actiniaria, Zoanthidea) from

mhydrothermal vents in the South-western Pacific. Marine Biology Research

2009

158 Appendix 1: Presence/absence matrix of the occurrence at hydrothermal vents globally of genera A) found in our quantitative collections or B) reported from the Lau Basin hydrothermal vent community. Presence is denoted by ‘1’ and absence is denoted by ‘0’. Genera in bold were not reported from the ELSC in Desbruyères et al. 2006. Site names: Lau = Lau Basin; N Fiji = North

Fiji Basin; Manus = Manus Basin, including Lihir Arc and Edison Seamount; Mariana = Mariana Trough; NZ = hydrothermal vents in New Zealand’s waters; NW Pacific = Okinawa Tough, Izu-Bonin Arc, Kaikata Seamount and Iheya Ridge; NE Pacific =

Gorda, Juan de Fuca and Endeavour Ridges; N EPR = Northern East Pacific Rise including the Galapagos Ridge and Guaymas

Basin; S EPR = Southern East Pacific Rise; MAR = Mid-Atlantic Ridge; CIR = Central Indian Ridge; PAR = Pacific-Antarctic

Ridge. Sources include 1) Desbruyères et al. 2006b, 2) Ramirez-Llodra et al. 2005, 3) Zelnio & Hourdez 2009, 4) Clarke & O’Shea

2001, 5) Stecher et al. 2002, 6) Hasegawa et al. 1997, 7) Ohta & Kim 2001, 8) Rodriguez et al. 2008, 9) Zelnio et al. In Press, 10) Lörz et al 2008, 11) Desbruyères et al. 2006a, 12) S. Ivanenko personal communication, 13) KAZ personal observation.

N NW NE N S Genus Lau Manus Mariana NZ MAR CIR PAR Source 159 Fiji Pacific Pacific EPR EPR

A Alviniconcha 1 1 1 1 0 1 0 0 0 0 1 0 1,2 Alvinocaris 1 1 1 1 1 1 0 1 0 1 0 0 1,2,3 Amphisamytha 1 1 1 1 0 1 1 1 0 0 0 0 1,2 Archinome 1 0 0 0 0 0 0 1 0 1 0 0 1,2 Austinograea 1 1 1 1 0 1 0 0 0 0 1 0 1 Bathyacmaea 1 1 1 1 0 1 0 0 0 0 0 0 1,2 Bathymodiolus 1 1 1 1 1 1 0 1 1 1 1 1 1,2,4,5 Branchinotogluma 1 1 1 1 0 1 1 1 1 0 0 0 1,2 Branchipolynoe 1 1 1 1 0 1 0 1 1 1 0 0 1,2 Bruciella 1 1 1 0 0 0 0 0 0 0 1 0 1,2 Chiridota 1 1 1 0 0 0 0 0 1 1 0 0 1,2 Chorocaris 1 1 1 1 0 1 0 0 1 1 0 0 1,2 Desbruyeresia 1 1 1 1 0 1 0 0 0 0 1 0 1,2,6 Eochionelasmas 1 1 1 0 0 0 0 0 1 0 0 0 1 Eosipho 1 1 1 1 0 1 0 0 1 0 0 0 1,2 Helicoradomenia 1 0 0 1 0 1 1 1 1 0 0 0 1,2 Hesiospina 1 0 0 0 0 0 1 1 1 0 0 0 1 Ifremeria 1 1 1 0 0 0 0 0 0 0 0 0 1 Imbricaverruca 1 0 0 0 0 0 0 0 0 0 0 0 1 Laeviphitus 1 0 0 1 0 1 0 0 0 1 0 0 1,2 Lepetodrilus 1 1 1 1 0 1 1 1 1 1 0 1 1,5 Lepidonotopodium 1 0 0 1 0 1 1 1 1 1 0 0 1,2 Leptogyra 1 0 0 0 0 0 0 0 0 0 0 0 1 Lurifax 1 0 0 0 0 1 0 0 0 1 0 0 1 Munidopsis 1 1 1 1 1 1 1 1 1 1 0 1 1,2,4,5,7 Nautilocaris 1 1 0 0 0 0 0 0 0 0 0 0 1 Oasisia 1 0 0 0 0 0 0 1 0 0 0 0 1 Olgasolaris 1 1 1 0 0 0 0 0 0 0 0 0 1,2 Pachydermia 1 1 1 1 0 0 0 1 1 0 0 0 1,2,6 Paralvinella 1 1 1 1 0 1 1 1 1 0 0 0 1,7 160 Phymorhynchus 1 1 1 1 1 0 0 1 0 1 0 0 1,4,6 Planorbidella 1 1 1 0 0 0 0 1 1 0 0 0 1,2 Prionospio 1 0 0 0 0 0 1 1 0 1 0 0 1,2 Protomystides 1 0 0 0 0 0 1 0 0 0 0 0 1 Provanna 1 1 1 1 0 1 1 1 1 0 1 0 1,2 Pseudorimula 1 1 1 1 0 1 0 0 0 1 0 0 1,2 Shinkailepas 1 1 1 1 0 1 0 0 0 1 0 0 1,2,6 Stygiopontius 1 1 1 1 0 1 1 1 0 1 0 0 1,2 Symmetromphalus 1 1 1 1 0 1 0 0 0 0 0 0 1,2 Thermiphione 1 1 1 0 0 0 0 0 1 0 0 0 1,2 Thermopolynoe 1 1 1 0 0 0 0 0 0 0 0 0 1 Thraumastros 1 1 0 0 0 0 0 0 0 0 0 0 1 Ventsia 1 1 1 1 0 0 0 0 0 0 0 0 1,2,6

B Abyssocladia 1 1 0 0 0 0 0 0 1 0 0 0 1,13 Acharax 1 1 1 0 0 0 0 1 0 0 0 0 1,2 Alaysia 1 1 1 0 0 1 0 0 0 0 0 0 1,2,7 Alvinactis 1 0 0 0 0 0 1 0 0 0 0 0 8,9 Anatoma 1 1 1 0 0 0 0 0 0 0 0 0 2 Arcovestia 1 1 1 0 0 0 0 0 0 0 0 0 1,2 Briarosaccus 1 0 0 0 1 0 0 0 0 0 0 0 10,13 Cephalochaetosoma 1 0 0 0 0 0 0 0 0 0 0 0 1 Chasmatopontius 1 1 1 1 0 1 0 0 0 0 0 0 1,2 Chondrophellia 1 0 0 0 0 0 0 1 1 0 0 1 1,9 Copidognathus 1 1 1 1 0 1 1 1 0 1 0 0 1,2 Cyananthea 1 0 0 0 0 0 0 1 0 0 0 0 1,9 Desmodora 1 0 0 0 0 0 0 1 0 0 0 0 1 Freyella 1 1 0 0 0 0 0 1 0 0 0 1 1,13 Heliocrenon 1 1 1 0 0 0 0 0 0 0 0 0 1,2 Hyalogira 1 1 1 0 0 0 0 0 0 0 0 0 2,11 Iphionella 1 1 1 0 0 0 0 1 0 0 0 0 2 Isaacsicalanus 1 0 0 0 0 0 0 1 0 0 0 0 2,12 161 Lamellibrachia 1 1 1 0 0 1 1 0 0 0 0 0 1,2 Lebbeus 1 1 1 1 0 1 1 1 0 0 0 0 2,13,7,11 Leptognathia 1 1 1 1 0 1 0 0 0 0 0 0 2,11 Munida 1 1 1 0 1 1 0 0 0 0 0 0 1,2,4,7 Neobrachylepas 1 1 1 0 0 0 0 0 0 0 0 0 1,2 Nicomache 1 0 0 1 0 1 1 1 0 0 0 0 1,2,11 Paralepetopsis 1 1 1 0 0 1 0 0 0 1 0 0 2 Paralomis 1 1 1 1 1 1 1 0 0 0 0 1 1,2,4,5,7 Pyropelta 1 1 1 0 0 0 1 1 0 0 0 0 2 Sagartiogeton 1 0 0 0 0 0 0 0 0 0 0 0 9 Siphonobranchia 1 1 1 0 0 0 0 0 0 0 0 0 1,2 Thermobiotes 1 1 1 0 0 0 0 0 0 0 0 0 1,2 Typhlotanais 1 1 1 1 0 1 0 0 0 1 0 0 2,11 Uroptychus 1 1 1 0 0 0 0 0 0 0 0 0 2 Vetulonia 1 1 1 0 0 0 0 0 0 0 0 0 2 Vulcanolepas 1 0 1 0 1 0 0 0 0 0 0 1 1,13 Xylodiscula 1 1 1 0 0 0 0 0 0 1 0 0 2