Cymbasoma markhasevae, 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 : 53-56

Cymbasoma markhasevae sp. nov.

( Figs 32 , 33 )

Material examined. Holotype: adult female from Warneet, Western Port Bay, Victoria, Australia (38°13.289’ S, 145°18.554’ E), partially dissected, ethanol-preserved; dissected parts mounted on slides in glycerine, sealed with Entellan®. Date of collection: 29th February 1984. Slides deposited in the collection of MTQ, Australia (cat. MTQ W34391).

Description of adult female. Body slender; total length of holotype female 1.41 mm. Cephalothorax approximately 0.92 mm long, representing 66% of total body length. Midventral oral papilla protuberant, located at 19% of cephalothorax length ( Fig. 32 C). Pair of relatively large ocelli present, pigment cups well developed, medially conjoined, separated by less than half an eye diameter, weakly pigmented; ventral cup as large as lateral cups. Frontal area ornamented with pattern of shallow transverse striations ( Fig. 32 B, C) and single pair of frontal sensilla ( Fig. 32 B). Anterior part of cephalothorax with fringe of transverse striae stretching around body from region of oral papillae and post-oral area. Ventral surface ornamented with few transverse striae between antennule bases and oral area. Additional ornamentation of ventral surface including: 1) three pairs of small, cuticular crescent-shaped processes between antennule bases, with no adjacent striae ( Fig. 32 B); 2) medial crescent-shaped process, larger than anterior paired processes; 3) pair of symmetrical nipple-like processes on anterior ventral surface located anterior to oral papilla, processes with concentric wrinkles and connected medially by transverse striae.

Urosome consisting of fifth pedigerous somite, genital double-somite and anal somite, together representing 13% of total body length. Relative lengths of urosomites (fifth pedigerous, genital double and free anal somites) 43.2: 33.3: 23.5 = 100, respectively ( Fig. 32 D, E). Lateral margins of fifth pedigerous somite straight. Fifth pedigerous somite longest of urosome, with straight lateral margins and wrinkles on dorsal and ventral surfaces ( Fig. 32 D, E). Genital double-somite relatively short, anterior half of somite moderately expanded, slightly tapering posteriorly, with transverse wrinkles on dorsal surface. Antero-ventral surface of somite protuberant ( Fig. 32 E). Ovigerous spines paired, separated at base, relatively short, 25% of total body length (0.35 mm). Spines slender, straight at their base and along shaft, distally acute. Anal somite medially constricted, with deep striae on lateral surface ( Fig. 32 D). Caudal rami weakly divergent, subrectangular, about 1.2 times as long as wide, armed with three caudal setae ( Fig. 32 D, F).

Antennule length 0.27 mm, representing about 19.4% of total body length and 28.4% of cephalothorax length, 4-segmented. Relative length of distal antennulary segment 52.3%. In terms of pattern described by Grygier & Ohtsuka (1995) for female monstrilloid antennulary armature, short, spiniform element 1 present on first segment; elements on second segment: 2d1-2, 2v 1-3, and IId. Third segment with strong spiniform element 3; IIId and IIIv of normal aspect. Segment 4 bearing elements 4d1, 4v 1-2, other element on group not observed; setae IVd, IVv, Vd, Vv, Vm, and 4aes present. Element 5 long, setiform. Subterminal elements b1–4 present, unbranched, elements 61-2 not present in specimens, but socket was observed on position of 61 ( Fig. 33 A).

Incorporated first pedigerous somite and succeeding three free pedigerous somites each bearing a pair of biramous legs. Pedigerous somites 2–4, together accounting for 20% of total body length. Legs 1–4 slightly increasing in size posteriorly. Intercoxal sclerites of legs 1–4 subrectangular, surface and posterior margin smooth. Bases of legs 1–4 articulating with large, rectangular coxa along oblique line; with hair-like lateral seta ( Figs. 33 B– D); on leg 3, this seta about 2.5 times longer, thicker than those on other legs ( Fig. 33 D). Endopods and exopods of legs 1–4 triarticulated. Ramal setae all biserially plumose except spiniform outer seta on exopodal segments 1 and 3, and inner seta of first exopodal segment, these latter being short, slender. Outermost distal spines on third exopodal segment of legs 1–4 short, 0.25 times as long as segment. Outermost apical setae on third exopodal segment of legs 1–4 with inner margin sparsely setulose, outer margin spinulose.

Armature formula of legs 1–4: Fifth legs medially conjoined, bilobate, outer (exopodal) lobe cylindrical, relatively short, with distal rounded process. Inner lobe arising basally, thumb-like, almost reaching distal margin of exopodal lobe. Exopodal lobe armed with three subapical setae, innermost seta slightly shorter than the other two ( Fig. 32 E, F).

Male: unknown.

Type locality. Warneet, Western Port Bay, Victoria, Australia (38°13.289’ S, 145°18.554’ E).

Etymology. The species is dedicated to Elena (Lena) Markhaseva, Zoological Institute of the Russian Academy of Sciences, for her contributions to the taxonomic knowledge of the planktonic Copepoda.

Diagnosis. Cymbasoma with long cephalothorax, representing 66% of total body length, third antennulary segment representing more than 52% of antennule length, with two pairs of crescent- like processes on ventral surface of cephalic region; additional medial crescent process. Cephalothorax with reduced but complete fringe of striation covering about 1/5 of cephalothorax. Genital double-somite shorter than fifth pedigerous somite, with tapering posterior half; urosomites with deep dorsal striae. Anal somite with medial constriction. Fifth leg with elongate, outer lobe with three setae, two distal and one subdistal, inner lobe arising basally, narrow, almost reaching distal end of outer lobe, unarmed.

Remarks. This species shares with other Australian female Cymbasoma ( C. bidentatum , C. annulocolle ) a fifth leg with a slender, elongate inner lobe arising proximally from the same base as the outer lobe that is armed with three subequal setae. Because of the presence of a fringe of striae partially covering the anterior section of the cephalothorax, it appears to be most closely related to C. annulocolle , because cephalic striation is absent in C. bidentatum . Some of the differences encountered in the genital double-somite between these species (i.e. relative size and presence of posterolateral processes and a lower anteroventral process) are presented in the remarks section of C. annulocolle . Some additional, subtle differences can be found in the antennulary armature; elements 2v 1-3 and 2d1-2 are clearly longer in C. annulocolle ( Fig. 14 A) than in the new species ( Fig. 33 A). The cephalothoracic ornamentation is different in these two species; the new species C. markhasevae has a set of three pairs of crescent-shaped processes between the antennule bases ( Fig. 32 B); these processes are absent in C. annulocolle , which in turn has a pair of papilla-like processes ( Fig. 13 C). In addition, the urosome, including the fifth pedigerous somite, the genital double-somite, and the anal somite have lateral and dorsal striae, whereas the surface of the urosomites is smooth in C. annulocolle except for a few lateral wrinkles on the anal somite ( Fig. 13 F). As explained in the comparative discussions of C. annulocolle below, the shape and proportions of the fifth pedigerous and genital double-somites is different in these species. In C. markhasevae the fifth pedigerous somite has straight lateral margins and lacks the postero-lateral rounded processes present in C. annulocolle . The genital double-somite is clearly wider and shorter in C. markhasevae than in C. annulocolle ; this somite is slightly longer than the fifth pedigerous somite whereas it is clearly shorter than the fifth pedigerous somite in C. markhasevae ( Fig. 32 D). The antero-ventral process of the genital double-somite is weakly developed in the new species and it is clearly stronger in C. markhasevae ( Fig. 32 E).

Figures

FIGURE 13. Cymbasoma annulocolle sp. nov., adult female from Werribee. A) habitus, lateral view; B) cephalic region, lateral view; C) same, ventral view; D) habitus, dorsal view; F) urosome and fifth legs, ventral view. Scale bars: A, D = 500 µm, B, C, E, F = 200 µm.

FIGURE 14. Cymbasoma annulocolle sp. nov., adult female. A) left antennule, dorsal view; B) first leg; C) third leg; D) fourth leg. Scale bars: A – D = 100 µm.

FIGURE 32. Cymbasoma markhasevae sp. nov., adult female. A) habitus, lateral view; B) cephalic region, ventral view; C) same, lateral view; D) urosome, dorsal view; E) same, lateral view, left fifth leg omitted to observe anteroventral protuberance; F) same, ventral view; G) fifth legs, ventral view. Scale bars: A = 200 µm, B – F = 100 µm, G = 50 µm.

FIGURE 33. Cymbasoma markhasevae sp. nov., adult female. A) right antennule, dorsal view; B) first leg; C) second leg; D) third leg. Scale bars: A = 50 µm, B – D = 100 µm.