Taxonomy of Oncaeidae (Copepoda, Cyclopoida S.L.) from the Red Sea
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE JOURNAL OF PLANKTON RESEARCH j VOLUME 31 j NUMBER 9 j PAGES 1027–1043 j 2009 provided by OceanRep Taxonomy of Oncaeidae (Copepoda, Cyclopoida s.l.) from the Red Sea. IX. Epicalymma bulbosa sp. nov., first record of the genus in the Red Sea RUTH BO¨ TTGER-SCHNACK†* LEIBNIZ-INSTITUTE FOR MARINE SCIENCES (IFM-GEOMAR), FB2 (BIOLOGICAL OCEANOGRAPHY), DU¨ STERNBROOKER WEG 20, D-24105 KIEL, GERMANY PRESENT ADDRESS: MOORSEHDENER WEG 8, D-24211 RASTORF-ROSENFELD, GERMANY. *CORRESPONDING AUTHOR: [email protected] Received April 3, 2009; accepted in principle June 1, 2009; accepted for publication June 3, 2009; published online 2 July, 2009 Corresponding editor: Mark J. Gibbons The oncaeid genus Epicalymma comprises small copepod species usually living at meso- and bath- ypelagic depth layers in oceanic areas. The genus had previously been assumed to be absent from the Red Sea, due to the unusually high deep-sea temperatures and salinities in this area. In the present account a new species, Epicalymma bulbosa, is described from the Red Sea, which appears to be the only representative of the genus in the region. The new species is the smallest Epicalymma species so far recorded, with a total body length of 0.32 and 0.29 mm in the female and male, respectively. Apart from its small size, it differs from all known Epicalymma species by an extremely long exopodal seta on P5 in both sexes, and by a free exopod segment of P5 and a very long and basally swollen spinule on the syncoxa of the maxilliped in the female. In contrast to other Epicalymma species, which are distributed between 500 and .2500 m depth, the new species occurred much shallower (100–750 m) in the Red Sea, which may be interpre- tated as an avoidance mechanism of the unfavourable environmental conditions in the deep Red Sea. The taxonomic status of the new species within the genus Epicalymma is discussed and the few available ecological data on Epicalymma species in the world ocean are summarized. INTRODUCTION species and are somewhat smaller than females, measuring between 0.43 and 0.67 mm in total body The genus Epicalymma was established by Heron length. Copepods of the genus Epicalymma are usually (Heron, 1977) in order to accommodate species of the found at depths .500 m and even down to . 2500 m, family Oncaeidae characterized by an outer spine count of II; III; III; I on the third exopod segments of the first though a single record from shallow inland waters to fourth swimming leg. Six species have been described (200 m depth) is also known (Heron and Frost, 2000). to date from various parts of the world ocean, including Unlike many other oncaeid microcopepods, whose mor- the temperate and tropical Atlantic (Farran, 1908; phological characteristics are inadequately known Gordeyeva, 1973), Arctic and Antarctic regions (Heron, (Bo¨ttger-Schnack et al., 2004), the morphology of most 1977; Heron et al., 1984; Heron and Bradford-Grieve, Epicalymma species has been described and/or (re)de- 1995) and the open NE Pacific as well as Washington scribed in sufficient detail by previous authors (Heron, inland waters (Heron and Frost, 2000). Epicalymma 1977; Heron et al., 1984; Heron and Bradford-Grieve, species are small-sized, with a female total body length 1995), including the antennule, the antenna and the ranging between 0.47 and 0.88 mm for the six known mouthparts. The detailed knowledge of these morpho- species. Males have so far been described for four logical characters has been recognized as indispensable doi:10.1093/plankt/fbp051, available online at www.plankt.oxfordjournals.org # The Author 2009. Published by Oxford University Press. All rights reserved. For permissions, please email: [email protected] JOURNAL OF PLANKTON RESEARCH j VOLUME 31 j NUMBER 9 j PAGES 1027–1043 j 2009 for the identification of oncaeid species, which other- compared with published data on Epicalymma species wise are very similar in morphology and include many from other areas of the world ocean. sibling species [e.g. (Heron and Bradford-Grieve, 1995; Bo¨ttger-Schnack, 1999, 2002, 2005)]. The taxonomic diversity of oncaeid microcopepods METHOD smaller than 0.5 mm in length is still insufficiently known, and quantitative ecological data on these small Epicalymma-type oncaeids were collected with a multiple copepods are scarce, due to the inadequate sampling opening–closing net (Weikert and John, 1981) with a methods and the difficulties in identifying the small mesh size of 0.055 mm during R/V “Meteor” cruise species (Krsˇinic´, 1998; Bo¨ttger-Schnack et al., 2004; 44/2 in 1999 in the northernmost Red Sea and the Nishibe and Ikeda, 2004). In particular, the Gulf of Aqaba (Table I). The sampling programme was deep-dwelling oncaeids of this size range have rarely part of an ecological and taxonomic study of the micro- been investigated both taxonomically and ecologically. copepod fauna in the Gulf of Aqaba (Bo¨ttger-Schnack The few quantitative data available on the community et al., 2001, 2008), conducted within the frame of a mul- structure of oncaeid microcopepods in mesopelagic and tidisciplinary research programme on the impact of bio- deep-sea layers point to a great numerical importance logical processes during early spring in the Gulf of the genus Epicalymma Heron, 1977 in these habitats (Pa¨tzold et al., 2000; Hempel and Richter, 2002). (Krsˇinic´, 1998; Krsˇinic´ and Grbec, 2002), accounting Presorted specimens from fine mesh net samples col- for up to 30% of the adult oncaeid population (Nishibe lected with the same equipment during cruise 5 of R/V and Ikeda, 2004; Nishibe, 2005; F. Krsˇinic´, unpublished “Meteor” in 1987 in the central and southern Red Sea data) and up to 5% of the total numbers of oncaeids, were also included in the taxonomic study (Table I). including juvenile stages (Bo¨ttger-Schnack, 1996, 1997). The vertical distribution pattern of Epicalymma bulbosa in In a comparative study of the oncaeid microcopepod the central and southern Red Sea was analysed by the fauna from the Red Sea and adjacent areas, the genus re-examination of material collected during earlier eco- Epicalymma had previously been assumed to be absent logical investigations of the microcopepod community from the Red Sea [(Bo¨ttger-Schnack, 1994) as Oncaea in these areas, and the methods of sampling and details sp. 5]. Improvement of the taxonomic resolution of Red of the quantitative enumeration have been described by Sea Oncaeidae lead to the detection of a very small as Bo¨ttger-Schnack (Bo¨ttger-Schnack, 1995). The plankton yet undescribed species belonging to this genus was initially fixed in 4% formaldehyde-seawater solution [(Bo¨ttger-Schnack et al., 2001, 2004) as Epicalymma sp.], buffered with borax (R/V “Meteor” cruise 44/2) or which will be described in the present paper. The verti- hexamethylene tetramine (R/V “Meteor” cruise 5). For cal distribution of the new species in the various regions sorting, the samples were transferred into a preservation of the Red Sea is presented, supplementing earlier eco- fluid of 5% propylene glycol, 0.5% propylene phenoxe- logical data from this area (Bo¨ttger-Schnack, 1995; tol and 94.5% filtered seawater (Steedman, 1976); after Bo¨ttger-Schnack et al., 2008), and the results are analysis they were returned into a 4% formaldehyde- Table I: Station list for sampling conducted with multiple opening–closing net with 0.055 mm mesh size during R/V “Meteor” Cruises 5 and 44 in the Red Sea Stn Date Geographic position Time, D5Day, N5Night Sampling, depth (m) Total water, depth (m) R/V “Meteor” Cruise 5 Central Red Sea 682 25.07.1987 21813.90N D 300–350 1880 38805.70E Southern Red Sea, oceanic area 703 02.08.1987 15834.80N D 450–600 970 41854.90E R/V “Meteor” Cruise 44/2 Northern Red Sea, main basin 156 04.03.1999 27825.000N D 300–350 798 34804.960E 500–550 550–650 Gulf of Aqaba 164 06.03.1999 29804.980N N 450–50 822 34845.960E 1028 R. BO¨ TTGER-SCHNACK j EPICALYMMA BULBOSA SP.NOV.,RED SEA seawater solution. Long-term storage in Steedman’s The family Oncaeidae has traditionally been placed fluid proved to be detrimental, as samples become in the order Poecilostomatoida. Following Huys et al. partly infected with fungi after . 10 years of preser- (Huys et al., 2002) and Boxshall and Halsey (Boxshall vation time (R. Bo¨ttger-Schnack, unpublished data). and Halsey, 2004), the latter and its constituent families Specimens were dissected in lactic acid, mounted on are now subsumed under the order Cyclopoida based slides in lactophenol and sealed with high-quality nail- on morphological grounds. Although this course of varnish. All figures have been prepared using a camera action has not universally been accepted yet [e.g. (Ho lucida on a Leitz Dialux differential interference con- et al., 2006)], recent molecular analyses using small trast microscope. subunit rDNA (18S) sequences have provided additional Total body length and the ratio of prosome to evidence for a close relationship between the cyclopoid urosome (excluding caudal rami) were calculated as the and poecilostomatoid families (Huys et al., 2006, 2007) sum of the middorsal lengths of individual somites and increased taxon sampling among the Cyclopoida measured in lateral view. In the case of telescoping rendered the latter paraphyletic at the exclusion of the somites, these lengths were measured from the anterior Poecilostomatoida (R. Huys, unpublished results). to posterior margin. This approach differs from that tra- ditionally used in oncaeid taxonomy, where the tele- scoping of somites is not considered in length RESULTS measurements.