Cymbasoma clairejoanae, 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 : 103-106

Cymbasoma clairejoanae sp. nov.

( Figs 60 , 61 )

Material examined. Holotype: adult male from Ross Creek, Townsville, Queensland, Australia (19°16.500’ S, 146°48.500’ E), partially dissected, ethanol-preserved; dissected parts mounted on 2 slides in glycerine, sealed with Entellan®. Date of collection: 19th October 1995. Slides deposited deposited in the collection of MTQ, Australia (cat. MTQ W34402).

Description of adult male. Total body length 0.63 mm. Cephalothorax 0.28 mm long, representing 44% of total body length ( Fig. 60 A, B). Midventral oral papilla weakly developed, located at 27% of cephalothorax length ( Fig. 60 C). Cephalic region protuberant bilaterally in dorsal view. Pair of dorsal ocelli present, moderately developed; pigment cups relatively large. Ocelli separated by the length of less than half an eye diameter, faintly pigmented. Ventral ocellus noticeably larger than lateral cups ( Fig. 60 D). No sensilla observed between antennulary bases. Forehead area strongly produced forming lumpy medial crest flanked by few wrinkles (arrowed in Fig. 60 C, D). Antero-ventral surface of head between antennulary bases and oral papilla with no protuberances. Dorsal surface of cephalic area smooth. Ventral surface with additional cuticular elements: 1) pair of symmetrical, crescent-shaped cuticular processes on anterior ventral surface between bases of antennules, with few adjacent striae ( Fig. 60 C); 2) nipple-like processes with adjacent transverse wrinkles; 3) few perioral transverse wrinkles.

Urosome consisting of fifth pedigerous somite, genital somite (carrying genital complex), preanal somite, and anal somite. Genital somite longer than fifth pedigerous somite. Genital complex of type II, represented by pair of moderately divergent, symmetrical slender, digitiform genital lappets resembling an inverted “U” ( Fig 61 A, B). Lappets posteriorly directed in lateral view ( Fig. 61 B), relatively long, almost reaching posterior margin of anal somite. Common basal joint of lappets flat, smooth ( Fig. 61 A). Lappet surface smooth. Anal somite noticeably long, about twice as long as preanal somite in dorsal view, comprising 33% of urosome length; constriction in proximal 1/3 of anal somite visible in ventral aspect, cuticular hyaline frill absent. Caudal rami subquadrate, approximately 1.1 times as long as wide, about 0.7 times as long as anal somite ( Fig. 61 C). Each ramus with four caudal setae.

Antennulary length 0.23 mm. Antennules relatively long, representing 36% of total body length, and 72% of cephalothorax length; 5-segmented, all segments separated, with segment 5 located distal to geniculation. Length ratio of antennulary segments, from first to fifth 11.4:27.8:12: 26.6: 22.2 (= 100). Setal element 1 on first segment short, spiniform. Antennulary elements 2v 1-3, 2d1,2 and IId present on second segment. Elements IIId, IIIv, and slender, curved spiniform element 3 present on third segment. Fourth segment with elements 4d1,2, 4v 1– 3, element 4v 1 being longest of group. Setae IVd and IVv present in specimen. Fifth segment with 5 “b”-group setae, elements b1-3 unbranched; element 6aes present in apical position. According to Huys et al. (2007) setal nomenclature of the distal segment, elements A–C, E and 3–7 present ( Fig. 61 D).

Incorporated first pedigerous somite and succeeding three pedigerous somites each bearing well-developed biramous legs. Pedigerous somites 2–4, together accounting for 29% of total body length in dorsal view. Exopods of legs 1–4 longer than endopods. Bases of legs 1–4 with hair-like lateral basipodal seta ( Fig61 E, F); on leg 3, this seta about 4.5 times longer, sparsely setulated and slightly thicker than those on the other legs ( Fig. 61 F). Endopods and exopods of legs 1–4 triarticulated. Ramal setae all biserially plumose except spiniform outer seta on exopodal segments 1 and 3. Flexible, slender, sparsely setulated inner seta present on first exopodal segment of legs 1–4. Outer spine on distal exopodal segment of legs 1–4 shorter than segment. Also, outermost apical exopodal setae of legs 1–4 with inner margin lightly setulose, outer margin spinulose.

Armature formula of legs 1–4 as follows:

Female: unknown.

Type locality. Ross Creek, Townsville, Queensland, Australia (19°16.5’ S, 146°48.5’ E).

Etymology. The species is named for Claire Joan Joan Grant (née McKinnon), daughter of the second author (DM).

Diagnosis. Cymbasoma with conspicuous medial protuberance on cephalic area with lumpy surface. First antennulary segment with short spiniform element 1; second segment with normal elements 2d1,2 and 2v 1-3. Antennule relatively long, representing 36% of total body length and 72% of cephalothorax length. Genital complex of type II, symmetrical, digitiform, with rounded distal tips, basal joint between lappets flat, smooth. Genital lappets long, almost reaching posterior margin of anal somite. Anal somite twice as long as preanal somite, with proximal constriction. Caudal rami with four setae.

Remarks. Cymbasoma clairejoanae sp. nov. is represented by the only Australian male Cymbasoma with four caudal setae, a strongly protuberant frontal area, and a constricted anal somite. It can readily be distinguished from its known congeners by the structure of the genital lappets which are long, slender, digitiform, and almost reaching the posterior margin of the anal somite. The margin between the insertions of the genital lappets is flat and wide, thus the complex appears as an inverted “U”-shaped structure. A similar genital complex is known only in C. pallidum Isaac, 1974 , which exhibits slightly curved, narrow, long genital lappets. The new species C. clairejoanae differs from C. pallidum in the presence of four caudal seta vs. three in C. pallidum ( Isaac 1974) and also in the presence of a corrugate frontal protuberance, which is very conspicuous in the new species ( Fig. 60 C, D) but absent from the flat frontal surface in C. pallidum (cf. Isaac 1974). Also, the anal somite of C. pallidum lacks a constriction which is clearly present in C. clairejoanae .

Figures

FIGURE 60. Cymbasoma clairejoanae sp. nov., adult male. A) habitus, dorsal view; B) same, lateral view; C) cephalic region, ventral view showing protuberant frontal process (arrow); C) same, dorsal view. Scale bars: A, B = 200 µm, C, D = 50 µm.

FIGURE 61. Cymbasoma clairejoanae sp. nov., adult male. A) urosome and genital complex, ventral view; B) same, lateral view; C) same, dorsal view; D) right antennule, dorsal view; E) first leg with smooth coxal plate; F) third leg with coxal plate. Scale bars: A – C, E, F = 100 µm, D = 50 µm.