Cymbasoma marioeduardoi, 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 : 78-81

Cymbasoma marioeduardoi sp. nov.

( Figs 46 , 47 )

Material examined. Holotype: adult male from Western Port Bay (Station G2 of Kimmerer & McKinnon 1985), Victoria, Australia (38°35.344’ S, 144°59.687’ E), partially dissected, ethanol- preserved; dissected parts mounted on 2 slides in glycerine, sealed with Entellan®. Date of collection: 24th November 1982. Slides deposited in the collection of MTQ, Australia (cat. MTQ W34398).

Description of adult male. Total body length 1.21 mm. Cephalothorax 0.58 mm long, representing 48% of total body length ( Fig. 46 A). Midventral oral papilla weakly developed, located at 21% of cephalothorax length ( Figs 46 A, B, 47A). Cephalic region protuberant bilaterally in dorsal view, with frontal area flat, bearing pair of short sensilla ( Fig. 47 A). Pair of relatively small dorsal ocelli present, weakly developed; pigment cups small. Ocelli separated by the length of less than one eye diameter, faintly pigmented. Ventral ocellus lightly larger than eyes. Other cuticular processes include: 1) medial rounded protuberance arising between antennulary bases (arrowed in Fig. 46 B), with smooth surface; 2) pair of nipple-like processes adjacent to medial protuberance, each with field of transverse striae stretching to oral area.

Urosome consisting of fifth pedigerous, genital somite (carrying genital complex), preanal somite, and anal somite. Fifth pedigerous somite with medial notch on ventral surface, straight lateral margins ( Fig. 46 D). Genital somite slightly shorter than fifth pedigerous somite, with wrinkles on dorsal surface and moderately expanded lateral margins. Preanal somite short, smooth, not constricted. Genital complex represented by pair of moderately divergent, wide-based, subtriangular genital lappets ( Fig. 46 D, E, F, G), these being slightly asymmetrical. Lappets relatively short, barely reaching beyond posterior margin of preanal somite, with row of five minute spiniform processes along inner margin of left lappet; right lappet with sinuous proximal inner margin ( Fig. 46 G). Thumblike medial process present at common basal joint of lappets, process distally bifurcate, with medial notch ( Fig. 46 G). Anal somite about twice as long as preanal somite in dorsal and lateral views, comprising 28% of urosome length; ventral surface distinctively protuberant forming two symmetrical globose processes visible in dorsal, lateral and ventral views ( Fig. 46 C, E, F).

Caudal rami subquadrate, approximately 1.2 times as long as wide ( Fig. 46 C), about 0.7 times as long as anal somite; each ramus with distinctive globose protuberance at insertion of lateral seta. Each ramus with three setae.

Antennulary length 0.32 mm. Antennules relatively short, representing 27% of total body length, and 55% of cephalothorax length; 5-segmented, all segments separated, with segment 5 located distal to geniculation ( Fig. 47 B). Length ratio of antennulary segments, from first to fifth 18.1: 21.9: 10.8: 28: 21.2 (= 100). Setal element 1 on first segment absent in both antennules (position arrowed in Fig. 47 B). Antennulary elements 2v 1-3, 2d1,2 remarkably long, slender; element IId present on second segment. Setal elements IIId, IIIv, and 3 present on third segment; latter element remarkably long, slender, almost reaching distal margin of fourth segment. Fourth segment with elements 4d1, 4v 1–2 present; setal elements IVd and IVv present in specimen. Fifth segment with 5 “b”-group setae, elements b1-3 dichotomously branched distally. According to Huys et al. (2007) setal nomenclature of the distal segment, elements A, B and 1–6 present. Apical elements 1 and 2 spiniform, remarkably long, curved, equally long ( Fig. 47 B).

Incorporated first pedigerous somite and succeeding three pedigerous somites each bearing well-developed biramous legs. Pedigerous somites 2–4, together accounting for 32% of total body length in dorsal view. Intercoxal sclerites of legs 1–4 subrectangular, surface with pattern of finely spinulose subquadrate fields, posterior margin smooth. Bases of legs 1–4 with hair-like lateral seta ( Fig. 47 C–E); on leg 3, this seta about 3.3 times longer ( Fig. 47 E). Endopods and exopods of legs 1–4 triarticulated. Ramal setae all biserially plumose except spiniform outer seta on exopodal segments 1 and 3. Inner seta of first exopodal segment absent, segment with spiniform process on distal margin ( Fig. 47 F). Outermost distal spines on third exopodal segment of legs 1–4 short in leg 1, 0.2 times as long as segment; element longer in legs 2–4, half as long as segment. Outermost apical exopodal setae of legs 1–4 with inner margin setulose, outer margin naked.

Female: unknown.

Type locality. Western Port Bay, Victoria, Australia (38°35.344’ S, 144°59.687’ E).

Etymology. The species is warmly dedicated to Mario Eduardo Suárez Gasca, son of the first author (ES-M).

Diagnosis. Cymbasoma with cephalothorax representing less than 50% of total body length; midventral oral papilla located at 21% of cephalothorax length. Cephalic region with anterior medial protuberance. Fifth antennulary segment with apical elements 1 and 2 (sensu Huys et al 2007) spiniform, remarkably long, equally long. Genital double-somite with moderately expanded lateral margins. Anal somite with pair of large, distinctive ventral protuberances visible also on dorsal view. Caudal rami each with conspicuous globular process at insertion of outer seta. Genital complex of Type II; genital lappets wide, subtriangular, asymmetrical; right lappet ornamented with minute dentiform processes; left lappet with sinuous proximal inner margin. Bifurcate process at common basal joint of lappets.

Remarks. This species is easily recognizable by several unique characters not present in any other known species of Cymbasoma . The conspicuous ventral protuberances on both the anal somite and the caudal rami are probably the most striking feature of this species. Among the Monstrilloida , a modified caudal ramus has been observed in the genus Australomonstrillopsis , displaying medial and distal lobes, but in the anal somite is not modified in this genus. Also, the genital complex, which is type II ( Suárez-Morales & McKinnon 2014), is remarkable for the distinctive medial process between the genital lappets, which is subtriangular with a distal notch; this condition is clearly different from the flat margin or sharply rounded processes found in other species of Cymbasoma . Also, the long, apical elements 1 and 2 (sensu Huys et al. 2007) on the last antennulary segment are also very unusual. In most species these elements are short and in other cases only one of them is elongate, as in C. williamsoni Khan, 1976 ( Khan 1976: fig. 3B), C. tumorifrons (cf. Suárez-Morales 1999), C. tropicum (cf. Sewell 1949), C. gracile (cf. Gurney 1927), C. spinapex (cf. Isaac 1974), and C. quintanarooense (cf. Suárez-Morales 2000a).

Figures

FIGURE 46. Cymbasoma marioeduardoi sp. nov., adult male. A) habitus, lateral view; B) cephalic region, detail of ventral protuberance; C) anal somite and caudal rami showing distinctive protuberances, ventral view; D) urosome, dorsal view; E) same, ventral view; D) same, lateral view; G) genital complex with lappets, ventral view. Scale bars: A = 200 µm, B, C, G = 50 µm, D – F = 100 µm.

FIGURE 47. Cymbasoma marioeduardoi sp. nov., adult female. A) cephalic region, ventral view; B) right antennule, dorsal view; C) first leg with coxal plate; D) second leg with coxal plate; E) third leg with coxal plate; F) detail of first exopodal segment of fourth leg showing distal tooth-like process. Scale bars: A, F = 50 µm, B – E = 100 µm.