BULLETIN DE L' INSTITUT ROYAL DES SCIENCES NATURELLES DE BELGIQUE, BIOLOG IE. 73: 167- 181, 2003• • BULLETIN VAN HET KONINKLIJK BELGISCH INSTITUUT VOOR NATU URWETENSCHAPPEN, BlOLOGlE, 73: 169- 181,2003 The phylogenetic position of the bathyal harpacticoids Aspinothorax gen. n. and Styracothorax HUYS (Crustacea: Copepoda) by Gisela MOURA & Pedro MARTINEZ ARBIZU Abstract Introduction Aspinothorax insolent is gen. et sp. n. is described fro m abyssal sites Harpacticoid copepods are usually the dominant arthropod in the Laptev Sea (Arcti c Ocean). The new genus is closely related g roup in marine benthic habitats. They have been reported to Styracothorax HUYS. The presence of a characteri stic sexual di­ from shallow waters to depths greater than I 0,000 m morphi sm on endopod of the second leg of male Aspinothorax gen. (BELYAEV, 1972). Deep-sea harpacticoid species usually be­ n. demonstrates its phylogenetic relationship with !dyella long to the families Argestidae (e.g. Argestes, Mesocletodes), (ldyanthinae: Tisbidae). As a consequence the harpacticoid family Paranannopidae (e. g. Cylindronannopus, Bathypsammis, Styracothoracidae HUYS is rejected, and its only genus and species Styracothorax gladiator HUYS is transferred to the Idyanthinae to­ Pseudomesochra), Tisbidae Idyanthinae (e. g. Zosime), and gether with the new genus. As a result of a re-evaluation of the fam­ Cerviniidae (e. g. Pontostratiotes) (e. g. BECKER, 1972, ily Ti sbidae, the fami ly Porcell idiidae is rejected, because its mem­ 1974 ; D1 NET, 1978; IT6, 1982, 1983). Recently a new deep bers are closely related with the ti sbid genera Sacodiscus and see family, Styracothoracidae has been described (B UYS, Scutellidiwn. 1993) o n the base o f a single female specimen collected from Key-words: Aspinothorax insolent is gen. sp. n. Styracothoracidae, an abyssal site off the Philippine west coast. In the course of Tisbidae, Harpacti coida, Copepoda, phylogenetic systematics. study of Arctic copepod biocenoses, minute harpacticoid specime ns were discovered in deep waters of the Laptev Sea. C lose examination of these specimens revealed them to be­ Resumen long to a new genus Aspin.othorax gen. n., closely related to Styracothorax B UYS . The discovery of m ale Aspinothorax Se describe Aspinothorax insolentis gen et sp. n. colectado en una gen. n. allows a re-evaluation o f the phylogenetic position of estaci6n abisal en el Mar de Laptev (Oceano Arti co ). El nuevo gene­ Styracothorax, to be discussed in the present contribution. ro estii emparentado con Styracothorax HU YS . La presencia de un The currently accepted system of Harpacticoida is based on caracterfsti co dimorphismo sexual en el end6podo de Ia segunda L ANG (1948). Unfortunately, L ANG 's system was no t pro­ pata en el macho de Aspinothorax demuestra Ia relaci6n duced using the methods of the phylogenetic systematic (e. g. filogenetica con !dye /Ia (ldyanthinae: Tisbidae). En consecuencia Ia H ENN IG, 1982), therefore it contains some polyphyletic and fa milia Styracothoracidae HUYS debe ser abolida y su linico genera paraphyletic groups. In the prese.nt contribution the families y especie S1yracothorax gladia1or transferida junto con el nuevo T isbidae (in the sense of LANG, 1948) and Porcellidiidae are genera a los ldyanthinae. Como resultado de una reevaluaci6n de la familia Ti sbidae, se propane la abolici6n de la fa mili a re-evaluated using a phylogenetic argumentation. Porcellidiidae, ya que sus miembros estan intimamente emparentados con generos de Tisbidae Sacodiscus y Scutellidium. Material and Methods Palabras Have: Aspinothorax insolentis gen. sp. n. Styracothoracidae, Tisbidae, Harpacti coida, Copepoda, sistematica M eio fauna samples were taken during the German-R ussian filogeneti ca. expedition to the Arctic Ocean ARK-IX/4 (Aug./Sept. 1993), o n board of RV Polarstern, using a Multicorer and a Giant­ B ox-Core r. Samples were fi xed immed iately after collection using formalin at a final concentration o f about 4% . Speci­ mens we re extracted by d ifferential notatio n using Levasil a nd transferred to glycerine for slide preparation. All draw­ ings were m ade w ith a Le itz Dialux p hase contrast micro­ scope using a camera Iuc ida. T he type mate rial is stored in the Senckenberg M useum in F rankfurt, Gem1any. '' 168 GISELA MOUA & PEDRO MARTiNEZ ARBIZU Description spinules, with 7 setae. Two setae inserting on outer margin, 2 setae subterminally on dorsal margin, 3 setae terminally (Fig. Aspinothorax gen. n. 7 A-B). Antennule 7-segmented, setal formula beginning with proxi­ Harpacticoida Oligoarthra. First thoracic somite fused to mal segment 1, 6, 3, 2 + aesthetasc, I, 2, 9 + aesthetasc (Fig. cephalosome. Rostrum small, fused to cephalothorax (Fig. 8 6 B). Seta on first segment arising from a horn-like pointed D). Furca about 14 times longer than median wide, with 7 process. Similar but minor processes on segments 2, 3, 4, and setae. Male antennule 10-segmented, with aesthetascs on 6th 5. and distal segments. Female antennule 7-segmented, with Antenna (Fig. 2 A) with defined asetose coxa and basis, and aesthetascs on 4th and distal segments. Antennary exopod !­ 2-segmented endopod. First endopodal segment with one segmented, carrying 6 setae. Mandibulary exopod !-seg­ outer seta pointing to inner margin, second compound seg­ mented, with 5 setae. Maxillulary exopod with 3 setae. ment ornamented with rows of spinules, with 3 lateral and 7 Maxilliped coxa with 2 setae, basis asetose, first and second terminal setae. Exopod elongate, !-segmented, with 3 lateral endopodal segments not separated, with 2 claw-like setae and 3 terminal setae. subterminally and 2 slender setae terminally. Leg 1 with 2- Mandible (Fig. 3 B), basis with 3 lateral setae, endopod !­ segmented exopod and !-segmented endopod, second segmented, with 1 lateral and 5 terminal setae. Exopod elon­ exopodal segment with 7 bipinnate setae. Leg 2 with 3-seg­ gated, !-segmented with 3 lateral and 2 terminal setae. mented exopod and 2-segmented endopod, distal endopodal Maxillule (Fig. 2 C), praecoxal arthrite with 10 terminal segment with 3 inner, 2 terminal and I outer seta in female; spines and 2 surface setae, coxal endite with I spine and 5 sexually dimorphic in male, with outer seta transformed into setae. Basis and endopod indistinctly fused with a total of 12 a short apophysis, outer terminal seta minute, and without setae, exopod bearing 3 setae. inner setae. Leg 3 with 3-segmented exopod and 2-seg­ Maxilla (Fig. 3 A), syncoxa with 4 endites. Proximal endites mented endopod. Leg 4 with 2-segmented exopod and !-seg­ fused together, with 3 setae and 2 setae and a claw. Distal mented endopod. Leg 5 with fused coxa, basis, exopod and endites with 2 setae and a claw each. Baseoendopod with one endopod; female with I outer basal seta, 3 exopodal setae strong claw flanked by 3 setae, additionally with 3 endopodal and 1 endopodal seta; male as female, but with 4 exopodal slender setae on inner margin, and one endopodal seta on an­ setae. Leg 6 asetose in both sexes. terior distal margin. Endopod indistinctly 3- segmented, with 2 geniculated setae on proximal and middle segments and TYPE SPECIES one geniculated seta and 3 slender setae on distal segment. Maxilliped (Fig. 2 B), syncoxa with 2 pinnate setae on inner Aspinothorax insolentis sp. n. margin. Basis asetose, with rows of spinules along outer and inner margins. Endopod !-segmented with a claw arising ETYMOLOGY from anterior margin on the middle of the segment, a stronger claw subterminally on inner margin and 2 slender setae ter­ The generic name is built by combining the Latin lexemes minally, which are apparently confluent at base. «a>>, «spina» and «thorax», meaning «back without spikes», Leg 1 (Fig. 4 A) with well developed praecoxa, coxa and ba­ and makes reference to the absence of horn-like processes on sis. Basis slightly transversely elongated, with an inner spine tergites, that are characteristic of its closest relative arising from a small protuberance and one outer seta. Styracothorax H UYS . Endopod !-segmented with 4 bipinnate setae. Exopod 2-seg­ mented, proximal segment with outer bipinnate seta, distal segment with 7 setae in total, all of them being slender and Aspinothorax insolentis sp. n. bipinnate. (Figs 1-9) Leg 2-4 (Figs. 5 A-B, 6 A). with transversely elongated bases, outer basal setae arising from a small protuberance on ante­ MATERIAL rior margin. Holotype one female, collected in the continental slope of the Spine and seta formula as follows: Laptev Sea at a depth of 3,428 m, September the 3rd 1993 (coordinates 79°39,00'N, 130°36, lO'E), dissected and Coxa Basis Exopod Endopod mounted in 18 slides (coli. no. SMF 28977), allotype one male collected in the continental slope of the Laptev Sea at a leg I 0-0 1-1 1-0; 3, 1,3 1, 1,2 depth of 3,2 11 m, September the 12111 1993 (coordinates leg 2 0-0 1-0 1-1; 1-1 ; III,I,3 0-1; 1,2,3 79°07,72'N, 122°52, 10'E), dissected and mounted on 6 0-0 1-0 slides, (coli. no. SMF 28978). leg 3 1-1 ; 1-1 ; 11,1,4 0- 1; 0,2,2 leg4 0-0 1-0 1-0; lll,I,2 0,1,2 FEMALE Body length 340 !-lJTl from tip of rostrum to posterior rim of Fifth leg with baseoendopod and exopod fused together (Fig. telson (Fig. 1 A-B). Furca elongate, about 14 times longer 7 A-B), bearing one outer basal seta, 3 setae on the exopodal than medjan wide, ornamented with longitudinal rows of lobe, and 1 seta on the endopodal lobe. With one Phylogenetic position of Aspinothorax gen. n.