Cymbasoma pseudoquadridens, Suárez-Morales, Eduardo & Mckinnon, David, 2016

Suárez-Morales, Eduardo & Mckinnon, David, 2016, The Australian Monstrilloida (Crustacea: Copepoda) II. Cymbasoma Thompson, 1888, Zootaxa 4102 (1), pp. 1-129 : 38-41

Cymbasoma pseudoquadridens sp. nov.

( Figs 22 , 23 )

Material examined. Holotype: adult male from Werribee, Port Phillip Bay, Victoria, Australia (37°57.085’ S, 144°47.128’ E), partially dissected, ethanol-preserved; dissected parts mounted on slide in glycerine, sealed with Entellan®. Date of collection: 13 June 1985. Vial and slides deposited in the collection of MTQ, Australia (cat. MTQ W34384).

Description of male. Total body length 1.24 mm. Cephalothorax 0.63 mm long, representing 51% of total body length ( Figs 22 A, 23A). Midventral oral papilla weakly developed, located at 24% of cephalothorax length ( Fig 22 D, 23A). Cephalic region protuberant bilaterally in dorsal view ( Fig. 22 B), with frontal field of striae. Cephalic region with field of striae limited to ventral surface between nipple-like processes and pre-oral region ( Fig. 22 C, D). Pair of dorsal ocelli present; pigment cups medium-sized. Ocelli separated by the length of less than one eye diameter, faintly pigmented. Ventral ocellus slightly larger than eyes. Frontal sensilla absent. Other cuticular processes include pair of nipple-like processes surrounded by short transverse striae.

Urosome consisting of fifth pedigerous, genital somite (carrying genital complex), preanal somite, and anal somite. Fifth pedigerous somite with smooth ventral surface, with no postero-lateral processes. Genital somite slightly shorter than fifth pedigerous somite. Genital somite with smooth dorsal surface and straight lateral margins. Preanal somite short, with smooth dorsal and ventral surfaces. Genital complex of type II (Suárez- Morales & McKinnon 2014), represented by pair of moderately divergent, robust thumb-like genital lappets ( Fig. 22 G), lappets symmetrical, reaching midlength of anal somite. Inner margin of lappets ornamented with row of 4 strong, sharp dentiform processes along proximal inner margins ( Fig. 23 E). Rounded, weakly protuberant medial process present at common basal joint of lappets. Anal somite about twice as long as preanal somite in dorsal and lateral views, comprising 24% of urosome length; anal somite not constricted ( Fig 22 E). Caudal rami subquadrate, approximately 1.1 times as long as wide, about as long as anal somite. Each ramus with four caudal setae.

Antennulary length 0.43 mm. Antennules relatively short, representing 35% of total body length, and 64% of cephalothorax length; 5-segmented, all segments separated, with segment 5 located distal to geniculation ( Fig. 23 B). Setal element 1 on first segment slender, spiniform, short. Antennulary elements 2v 1-3, 2d1,2 long, slender; element IId present on second segment. Setal elements IIId, IIIv, and long element 3 present on third segment. Fourth segment with elements 4d1,2, 4v 1–3 present; element 4v 1 being longest of group (asterisk in Fig. 23 B); except for seta IVv, all other setae absent in specimen. Fifth segment with 4 “b”-group setae, elements b1-3 slender, long, unbranched; element 61 present in distal position. According to Huys et al. (2007) setal nomenclature of distal segment, elements A, B, and E and 1, 2–6 present; element 2 stout, spiniform, curved.

Incorporated first pedigerous somite and succeeding three pedigerous somites each bearing well-developed biramous legs. Pedigerous somites 2–4, together accounting for 30% of total body length in dorsal view. Legs 1–4 as in C. bitumidum except for surface of coxal plates ornamented with spinulose patches ( Fig. 23 C, D).

Type locality. Werribee, Port Phillip Bay, Victoria, Australia (37°57.085’ S, 144°47.128’ E).

Etymology. The species name refers to the resemblance of this copepod to C. quadridens , a species originally described by Davis (1947) as having four tooth-like processes on the genital lappets, like the new species.

Diagnosis. Cymbasoma with ventral field of striae on cephalic region plus transverse frontal wrinkles. Antennulary fifth segment with long, stout apical element 1 (sensu Huys et al. 2007). Genital complex of Type II; genital lappets reaching beyond halflength of anal somite, ornamented with 4 strong, sharp dentiform processes along proximal inner margins and with low rounded process at common basal joint of lappets. Anal somite not constricted.

Remarks. This is another species of Cymbasoma whose male bears four caudal setae. It differs from its congeners sharing this character in the lack of a ventral protuberance, which is present in C. bullatum (Suárez- Morales, 2007), C. rochai ( Suárez-Morales & Dias, 2001) and the Australian C. bitumidum sp. nov. The main distinctive character of this species is the structure and ornamentation of its genital lappets. It has four strong spines on the inner proximal margin of the lappets; only a few species have this kind of ornamentation. The Australian C. annulocolle has a serrated row of 6–10 small spiniform processes ( Fig. 17 E, G), thus differing from the pattern observed in the new species. Also, it has three caudal setae vs. four such setae in the new species and has a fringe of striae around the cephalic region, a character absent in the new species. Another species with a row of spines along the inner margin of the lappets is C. quadridens Davis, 1947 , but the lappets are relatively shorter and more robust than in the new species and spines are clearly smaller and weaker ( Suárez-Morales & Pilz 2008). Also, C. quadridens has three caudal setae vs. four in the new species. The antennule apical element 2 is about twice as long as that depicted by Davis (1947) and Suárez-Morales & Pilz (2008) for C. quadridens . The lappets of C. mcalicei Suárez-Morales, 1996 have a corrugate inner margin ( Suárez-Morales1996: fig. 2E) which clearly diverges from the strong spines present in the new species.

Figures

FIGURE 17. Cymbasoma annulocolle sp. nov., adult males from Werribee. A) urosome and genital complex, ventral view; B) same, dorsal view; C) cephalic region, lateral view, specimen B; D) specimen A, detail of genital complex, ventral view; E) detail of ornamentation of genital lappets, specimen A; F) specimen B, detail of genital complex, ventral; G) detail of ornamentation of genital lappets, specimen B. Scale bars: A – C = 100 µm, D, F = 50 µm, E, G = 20 µm.

FIGURE 22. Cymbasoma pseudoquadridens sp. nov., adult male. A) habitus, dorsal view; B) cephalic region, dorsal view; C) same, ventral view; D) same, lateral view; E) urosome, dorsal view; F) same, showing genital complex, lateral view; G) same, ventral view. Scale bars: A = 200 µm, B – G = 100 µm.

FIGURE 23. Cymbasoma pseudoquadridens sp. nov., adult male. A) habitus, lateral view; B. right antennule, dorsal view; C) first leg; D) third leg with coxal plate; E) detail of ornamentation of genital lappets, ventral view. Scale bars: A = 200 µm, B, E = 50 µm, C, D = 100 µm.