Zootaxa,Speleonectes Emersoni, a New Species of Remipedia

Speleonectes emersoni, a new species of Remipedia (Crustacea) from the Dominican Republic

DÖRTE LORENTZEN1, STEFAN KOENEMANN1 & THOMAS M. ILIFFE2 1Institute for Animal Ecology and Cell Biology, University of Veterinary Medicine Hannover, Buenteweg 17d, 30559 Hannover, Germany 2Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX 77553-1675, USA Correspondence to second author. E-mail: [email protected]

Abstract

A new species of Remipedia (Crustacea), Speleonectes emersoni, is described from two anchialine caves in the Domini- can Republic. It represents the first record of remipedes for the island of Hispaniola. Speleonectes emersoni is a comparatively small-sized remipede. It can be distinguished from other species in the genus Speleonectes by a combination of features that include: 1) a relatively large antennal exopod, 2) frontal filaments with subapically inserted medial processes extending over the tip of the main filament, 3) an arc-shaped horseshoe-type claw with 7–10 small denticles, and 4) an anal segment that is longer than wide with caudal rami nearly as long as the anal segment.

Key words: Crustacea, Remipedia, Speleonectidae, anchialine caves, Dominican Republic, biogeography

Introduction

To date, the crustacean class Remipedia Yager, 1981 includes three families: Speleonectidae Yager, 1981, composed of thirteen species in four genera (Cryptocorynetes Yager, 1987, Kaloketos Koenemann et al., 2004, Lasionectes Yager & Schram, 1986, Speleonectes Yager, 1981), Godzilliidae Schram, Yager & Emer- son, 1986, with three species in three genera (Godzilliognomus Yager, 1989, Godzillius Schram, Yager, Emer- son, 1986, Pleomothra Yager, 1989), and Micropacteridae Koenemann et al. (2007a), with the monotypic genus Micropacter. Herein we describe a new species, Speleonectes emersoni, that was collected from two caves in the south of the Dominican Republic near Santo Domingo in May 2005. This southern extension to the range of Carib- bean remipedes indicates that the group is more widespread than previously known.

Definitions of morphological terms

In remipede systematics, the terms 'seta' and 'spine' have been used traditionally to distinguish between slender and more robust setal structures. However, Wollermann et al. (2007) followed Watling’s (1989) distinction between a spine and a seta when describing a new remipede species. Watling defined a spine as a non-articulated cuticular extension that has no socket, regardless of its size or shape. A seta, on the other hand, is “an articulated cuticular extension of virtually any shape or size”. Examination of numerous SEM photos of vari- ous species suggest that all remipedes are equipped with a relatively large diversity of multi-functional setae, while spines sensu Watling are only present as cuticular outgrowths in some species, for example, the pointed

Accepted by J. Olesen: 7 Jun. 2007; published: 6 Aug. 2007 61 pleurotergites or the posterolateral projections of the head shield in Pleomothra. Therefore, we will also adopt the terminology proposed by Watling in this paper and refer to 'spines' as stout (or spiniform) setae. The terms 'brachium' and 'lacertus' were introduced by Koenemann et al. (2007a). For convenience, we repeat the definitions of both terms. brachium (Lat. bracchium, -i, n.; “lower arm to wrist”'): In the maxillule, maxilla and maxilliped, this term defines all segments distal to the elbow including the claw. lacertus (Lat. lacertus, -i, m.; “upper arm”): Refers to the typically expanded segment immediately proximal to the elbow in the maxillule, maxilla, and maxilliped.

Systematics

Speleonectes emersoni new species (Figs. 1–4)

Type locality. Cueva Los Jardines Orientales, south coast near Santo Domingo, Dominican Republic. Material examined. Holotype (deposited at Biozentrum Grindel und Zoologisches Museum, Hamburg; catalogue number K - 41270) (12.5 mm, 21 trunk segments), five paratypes (9.5 mm, 19 trunk segments; 10.5 mm, 20 trunk segments; 11 mm, 20 trunk segments; 11 mm, 20 trunk segments; 11.5 mm, 20 trunk segments; all in research collection of SK) from Cueva Los Jardines Orientales. One paratype (10 mm, 20 trunk segments) from Cueva Taina. Specimens were collected on May 1, 2005 (Cueva Taina) and May 5, 2005 (Cueva Los Jardines Orientales) at or below the halocline in 15–37 m depth by Thomas Iliffe. The holotype and one paratype (whole specimens) are preserved in alcohol; two paratypes were dissected and preserved in glycer- ine; three paratypes were used for molecular analyses. Etymology. The epithet emersoni is in honor of the biologist Michael James Emerson (8 May 1954 – 22 March 1990). Michael worked as a research assistant on the “Remipede Project” at the San Diego Natural History Museum from 1982 to 1990. His experience as a skillful scientific illustrator and attentive observer resulted in several publications that set benchmarks in the systematics of Remipedia. Diagnosis. A small-sized, slender species, up to 12.5 mm, adult specimens composed of 19–21 segments; pleural tergites weakly developed, with rounded lateral margins in anterior part of trunk, becoming slightly pointed in posterior trunk; dorsal ramus of antennule 11-segmented, ventral ramus with 6 segments; arc- shaped, horseshoe-like claw of maxilla and maxilliped composed of 7–10 denticles; anal segment longer than wide; caudal rami approximately as long as anal segment. Description. Based on holotype and paratypes. Body slender with a maximum length of 12.5 mm and 21 trunk segments (Fig. 1). Pleural tergites narrow, with rounded distolateral corners on trunk segments 1–7 (Figs. 1, 2A), becoming slightly acuminate in posterior part of trunk, tergite on first trunk segment reduced. Sternal bars sublinear and isomorphic. Male gonopores on trunk limb 14 cylindrical, with rounded pointed lobes (Fig. 2B). Head shield subrectangular, tapering at anterior end, approximately as long as trunk segments 1–3 (Fig. 2A). Frontal filaments with relatively short distomedial processes, extending beyond tip of main filament (Fig. 3A). Antennule (Fig. 3B): Peduncle with small bulbus bearing relatively few aesthetascs. Dorsal flagellum 11- segmented, almost twice as long as head shield, reaching 9% of length of body. Ventral flagellum with 6 segments, nearly half as long as dorsal flagellum, as long as head shield. Antenna (Fig. 3C): Proximal segment of protopod with 2 marginal setae; distal segment with 4 marginal setae. Exopod longer and wider than adjacent distal segment of protopod, bearing 18–20 long setae. Endopod bent in a semicircular arc; first two proximal segments with 5–6 and 4–5 setae, respectively; distal segment with about 15 setae arranged in two rows composed of 9 and 5–6 setae. All setae faintly plumose.

62 · Zootaxa 1543 © 2007 Magnolia Press LORENTZEN ET AL. FIGURE 1. Speleonectes emersoni n. sp. from Dominican Republic. Left: 12.5 mm holotype (dorsal view); right: 11.0 mm paratype (ventral view); specimens approximately at same scale.

Mandible (Fig. 3D, E): Right incisor process and lacinia mobilis with three large denticles. Left incisor process with four large denticles; left lacinia mobilis crescent-shaped, apical margin serrate. Molar process prominent. Maxillule (Fig. 4A, D, E): Segment 1 with slender endite, distal margin terminating in 4 long stout setae (one of which prominent) and about 3 simple setae. Endite of second segment long and broad, with 2 setae at inner proximal margin; 6 stout, relatively large setae (all of which simple, except one setulose seta (Fig. 4E)) and 5–6 fine setae arranged in a second row on distomedial and -lateral margins and two long setae on disto-

A NEW SPECIES OF REMIPEDIA (CRUSTACEA) Zootaxa 1543 © 2007 Magnolia Press · 63 lateral margin. Segment 3 short; endite tapering, slightly rounded, bearing 2 long, robust setulose setae and 1 simple seta. Segment 4 (lacertus) subtriangular, with obliquely expanded medial margin; proximal corner bearing 2 long, robust setae (Fig. 4D) and 4–5 simple setae. Segment 5 as long as lacertus, but narrower, with a cluster of distomedial setae. Sixth segment equipped with separate clusters of long and shorter setae on distal margins. Claw slender, well-developed (Fig. 4A). Maxilla (Fig. 4B): First endite of segment 1 bearing 2 short apical stout setae. Endites 2 and 3 of first segment each with 1 prominent apical stout seta accompanied by 2–4 short setae on subapical margins. Endite of segment 2 equipped with a single, short stout seta and a few long setae. Segment 3 (lacertus) slightly pear- shaped, medial margin bearing 4–6 long and short setae. Segment 4 shorter than segment 3; distomedial margin rounded, with a cluster of 2–3 setae. Segment 5 shorter than segment 4, subquadrangular; distomedial corner with a cluster of 5 long and shorter setae. Segment 6 nearly as long as segment 5, with a row of about 7 setae along distomedial margin and a row of about 6 setae on distoposterior margin. Arc-shaped, horseshoe- type claw serrated, composed of 7–10 small denticles flanked by 2 stronger, separate denticles. All setae simple.

FIGURE 2. Speleonectes emersoni n. sp. from Dominican Republic, 12.5 mm holotype. A, dorsal view of head shield with trunk segments 1–3 (scale bar = 0.5 mm). B, D, 14th thoracopod, with enlarged detail of stout serrated setae on distolateral corner of segment 2 of exopod (scale bar = 0.2 mm). C, anal segment and caudal rami (scale bar = 0.4 mm).

64 · Zootaxa 1543 © 2007 Magnolia Press LORENTZEN ET AL. FIGURE 3. Speleonectes emersoni n. sp. from Dominican Republic, 12.5 mm holotype. A, frontal filaments (scale bar = 0.05 mm). B, antennule (scale bar = 0.3 mm). C, antenna. D, left mandible with enlarged lacinia mobilis and incisor process. E, enlarged incisor process (left) and lacinia mobilis (right) of right mandible. Scale bars C and D = 0.1 mm.

A NEW SPECIES OF REMIPEDIA (CRUSTACEA) Zootaxa 1543 © 2007 Magnolia Press · 65 FIGURE 4. Speleonectes emersoni n. sp. from Dominican Republic, 12.5 mm holotype. A, maxillule. B, maxilla. C, maxilliped. D, long, slender robust seta of lacertus of maxillule. E, setulose stout seta of maxillule. F, claw of maxilliped. Scale bars A–C = 0.2 mm. Numbers indicate individual limb segments.

66 · Zootaxa 1543 © 2007 Magnolia Press LORENTZEN ET AL. Maxilliped (Fig. 4C, F): Distinctly longer than maxillule, slender. Segments 1 and 2 bearing a few long medial setae. Segment 3 rather long, with 4 long setae. Segments 4–6 gradually decreasing in length; fourth segment with a row of 4 medial setae. Segment 5 with distomedial margin slightly expanded bearing 2 long setae. Segment 6 bearing 2 setae on distomedial margin. Segment 7 subquadrangular, with a row of about 6 long and shorter setae at distomedial margin. Eighth segment approximately as long as segment 7, equipped with a row of about 13 setae at distomedial margin and 7 short setae on distolateral margin. Claw subequal to that of maxilla (Fig. 4F). All setae simple. Trunk appendages (Fig. 2B, D): Segment 1 of exopod equipped with 3–6 long setae and up to 2 serrate stout setae on distolateral corner. Segment 2 with setae on lateral and medial margins, and 3–4 serrate stout setae on distolateral corner. Segment 3 ovate, bearing 14–17 long marginal setae. Endopod slightly shorter and narrower than exopod; distribution of long plumose setae like those on exopod, with the following excep- tions: basal segment naked; segment 3 with 2 serrate stout setae on distolateral corner and 1 serrate stout setae on distomedial corner; segment 4 with 10–12 setae (Fig. 2B). All setae plumose. Anal segment (Fig. 2C): 1.2 times longer than wide; caudal rami about 1.1 times longer than anal segment, bearing a few very fine setae along margins and about 3 fine, apical setae.

Morphological comparison with other species

Speleonectes emersoni is a relatively small sized species without any of the distinct modifications that define the two families Godzilliidae and Micropacteridae. The new species is placed in the genus Speleonectes based on the following characters: (1) the three pairs of prehensile, postmandibular appendages bear only a few clusters of sparsely inserted setae; (2) individual segments of maxilla and maxilliped are not distinctly modified (expanded, narrowed, fused or elongated); (3) the pleurotergites of the trunk are comparatively narrow; (4) the ventral ramus of the antennula is not reduced. Some of these features are similar in two Bahamian species, S. epilimnius Yager & Carpenter, 1999 and S. tanumekes Koenemann et al., 2003. These two species are mor- phologically closer to S. emersoni than any other speleonectid. Morphologic affinities and differences with Speleonectes epilimnius: Both S. emersoni and S. epilimnius have weakly developed pleurotergites. However, in S. emersoni, the outer posterior margins are more rounded. Moreover, the medial process of the frontal filaments is longer and the lacertus of the maxillule is more sharply triangular in shape in S. emersoni. In addition, S. emersoni has a relatively large antennal exopod in comparison to S. epilimnius, and the anal segment is longer than wide, with the caudal rami nearly as long as the anal segment. In S. epilimnius, by contrast, the anal segment is also longer than wide, but the caudal rami are 2–2.5 times longer than the anal segment. Morphological comparison with Speleonectes tanumekes: In S. emersoni, the dorsal flagellum of the antenna is composed of 11 segments (13 segments in S. tanumekes). Moreover, the medial processes of the frontal filaments are longer and the lacertus of the maxillule is more triangular in S. emersoni than in S. tanumekes. S. emersoni can also be clearly distinguished from S. tanumekes by the number of denticles within the arc of the horseshoe-type claw (7–10 in S. emersoni versus 17–20 in S. tanumekes). The anal segment is longer than wide in S. emersoni; in S. tanumekes, the anal segment is wider than long.

Locality profiles

Cueva Los Jardines Orientales is located 20 km east of Santo Domingo and 2.8 km inland from the south coast of the Dominican Republic at 18° 28.843' N, 69° 42.128' W. The collapse entrance consists of a breakdown slope extending about 15 m down from the surface to a pool and the beginning of an underwater cave. This

A NEW SPECIES OF REMIPEDIA (CRUSTACEA) Zootaxa 1543 © 2007 Magnolia Press · 67 extensive submerged cave system contains a halocline separating freshwater from underlying fully marine water. Maximum water depth was 34 m. Remipedes were found exclusively in the deeper, marine waters, along with copepods and stygiomysids, while shrimp and amphipods were found in the freshwater layer. Cueva Taina (also known as Cueva La Sirena) is situated 11 km east of Santo Domingo and 1 km inland from the south coast of the Dominican Republic at 18° 28.461' N, 69° 46.841' W. The two caves containing S. emersoni are separated by a distance of 8 km. Cueva Taina is entered by way of a spiral staircase that descends to a sea level pool. The cave has been explored by divers for more than 830 m horizontally, reaching a maximum depth of 41 m. A halocline at 15 m depth separates overlying freshwater from deeper, fully marine water. Also collected from the cave were halocyprid ostracodes, amphipods, and stygiomysids. The caves on Hispaniola represent the most southern localities for Remipedia in the larger Caribbean region. The nearest localities to the north are the Turks and Caicos Islands, where four species of remipedes are known to occur (Koenemann et al., 2007b)

Acknowledgments

Anchialine cave biology research was funded by a grant from the Biodiversity Surveys and Inventories Pro- gram of the National Science Foundation (DEB-0315903) to T. Iliffe. Biological collections reported on here were made during the May 2005 Advanced Diver Magazine expedition to the Dominican Republic that included team members Curt Bowen, Jill Heinerth, and Jim Rozzi and was organized by Uwe Rath and the Pirate’s Cove Dive Center in the Dominican Republic. We also thank Denis Bourret of the Golden Arrow Technical Diving Center in Santo Domingo for considerable logistical and cave diving assistance.

References

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