Cymbasoma

Suárez-Morales, Eduardo & Mckinnon, David, 2016, The Australian Monstrilloida (Crustacea: Copepoda) II. Cymbasoma Thompson, 1888, Zootaxa 4102 (1), pp. 1-129 : 120-123

Cymbasoma sp.

( Figs 70 , 71 )

Material examined. Damaged adult female (lacking antennules) from Rhyll, Western Port Bay, Victoria, Australia (38°26.792’ S, 145°18.496’ E), partially dissected, ethanol-preserved; dissected parts mounted on slide in glycerine, sealed with Entellan®. Date of collection: 19th May 1985. Slide deposited in the collection of MTQ, Australia (cat. MTQ W34406).

Description of adult female. Body slender, with elongate cephalothorax ( Fig. 70 A, B); body length 1.35 mm. Cephalothorax approximately 0.89 mm long, representing 66% of total body length. Midventral oral papilla weakly protuberant, located at 31% of cephalothorax length. Pair of relatively small ocelli present, pigment cups moderately developed, separated by 1.3 times an eye diameter, weakly pigmented; ventral cup about 1.5 times as long as lateral cups ( Fig. 70 C). Cephalic area as wide as cephalothorax, with flat "forehead” ornamented with transverse wrinkles ( Fig. 70 C); pair of frontal sensilla present. Dorsal surface of cephalothorax smooth except for fringe of cephalic reticulation between ocelli and preoral area ( Fig. 70 C). Ventral surface ornamented with 1) medial corrugate protuberance posterior to bases of antennules (asterisk in Fig. 70 C); 2) pair of nipple-like processes with few transverse wrinkles.

Urosome consisting of fifth pedigerous somite, genital double-somite and anal somite, together measuring 0.18 mm and representing 14% of total body length. Fifth pedigerous somite with slightly expanded lateral margins, dorsal and ventral surfaces smooth. Genital double-somite longest of urosome, ventrally protuberant, with lateral margins expanded into globose shape; ventral surface ornamented with few transverse wrinkles at insertion of ovigerous spines ( Fig. 70 D). Ovigerous spines paired, basally separated, slender, straight at their bases ( Fig. 70 D), relatively short (0.39 mm long), 29% of total body length. Anal somite shortest of urosome, with no constriction; dorsal and ventral surfaces smooth ( Fig. 70 E). Caudal ramus subrectangular, about 1.3 times as long as wide, armed with three caudal setae, ramus slightly longer than anal somite.

Antennules broken off in examined specimen, only the first two segments of the left antennule remaining; armature details not analyzed. Pedigerous somites 2–4, together accounting for 23% of total body length. Intercoxal sclerites of legs 1–4 subrectangular, surface with patches of minute spinules, posterior margin smooth, slightly curved. Bases of legs 1–4 with hair-like lateral seta ( Fig. 71 A-C); on leg 3, this seta sparsely setulose, about four times longer, thicker than those on other legs ( Fig. 71 A). Endopods and exopods of legs 1–4 triarticulated. Outermost distal spines on third exopodal segment of legs 1–4 short, 0.2 times as long as segment. Outermost apical exopodal setae of legs 1–4 with inner margin setulose, outer margin spinulose.

Armature formula of legs 1–4: Fifth legs medially conjoined, bilobate; outer (exopodal) lobe elongate, cylindrical, distally truncate; armed with two equally long apical setae ( Fig. 70 D, F). Inner lobe arising basally, short, unarmed, reaching about halflength of exopodal lobe.

Male: unknown.

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

Remarks. The absence of antennules prevented a full description of this species. It appears to belong to the group of Australian Cymbasoma species that have an outer lobe of the fifth leg armed with two setae, i.e. the agoense group. It has certain affinities with members of this group and possibly represents another undescribed species; however, we prefer to retain this species as “sp.” until a complete set of morphological data becomes available.

Figures

FIGURE 70. Cymbasoma sp., adult female. A) habitus, lateral view; B) same, dorsal view; C) cephalic region, lateral view, ventral medial protuberance marked by asterisk; D) urosome, ventral view; E) same, dorsal view; F) detail of fifth leg. Scale bars: A, B = 200 µm, C – E = 100 µm, F = 50 µm.

FIGURE 71. Cymbasoma sp., adult female. A) first leg; B) second leg; F) third leg with coxal plate. Scale bars: A – C = 100 µm.