Cymbasoma bali Desai & Krishnaswamy, 1962

Suárez-Morales, Eduardo & Mckinnon, David, 2016, The Australian Monstrilloida (Crustacea: Copepoda) II. Cymbasoma Thompson, 1888, Zootaxa 4102 (1), pp. 1-129 : 45-52

Cymbasoma bali Desai & Krishnaswamy, 1962

( Figs 26–31 )

Material examined. Three adult females from near Queenscliff, Port Phillip,Victoria, Australia (38°16.085’ S, 144°40.081’ E; Station Q of Kimmerer & McKinnon 1985); one adult female from Davies Reef, Queensland, Australia (18° 48.78' S, 147° 39.30' E), 2 specimens partially dissected; dissected parts mounted on slide in glycerine, sealed with Entellan®. Date of collection: 26th February 1984 and 20th June 1989, respectively. Slides deposited in the collection of MTQ, Australia (cat. MTQ W34388, MTQ W34389, MTQ W34390, MTQ W34387, respectively).

Description of adult female. Body moderately robust; body length of four females 1.3 (Davies Reef), 1.94, 1.76, and 1.85 mm (Queenscliff). Average length (n =4) 1.71 mm. Cephalothorax approximately 1.03 mm long, representing 60–61% of total body length. Midventral oral papilla noticeably protuberant, located at 19–20% of cephalothorax length. Pair of relatively large ocelli present, pigment cups well developed, medially conjoined, separated by less than half an eye diameter, intensely pigmented at inner edges; ventral cup as large as lateral cups ( Figs. 26 B, C). Cephalic area not laterally protuberant. Frontal area ornamented with pattern of shallow transverse striations ( Fig. 26 C, D) and single pair of short frontal sensilla ( Fig. 26 C). Dorsal surface of cephalothorax smooth ( Fig. 28 A: Queenscliff) or with field of faint transverse wrinkles on anterior position at same level of oral papilla ( Fig. 26 B: Davies Reef). Ventral surface ornamented with few transverse striae between antennule bases and oral area ( Fig. 26 C). Additional ornamentation of ventral surface including: 1) one ( Fig. 26 D) or two ( Fig. 28 B) pairs of small, cuticular crescent-shaped processes between antennule bases, with peripheral striae; 2) single pair of minute papilla-like processes between nipple-like processes and oral area ( Fig. 28 B); these processes absent in specimen from sta. 34 ( Fig. 26 D); 3) pair of symmetrical nipple-like processes on anterior ventral surface located at both sides of oral papilla, processes connected medially by field of transverse striae ( Figs. 27 C, 30B, C, 31A–C).

Urosome consisting of fifth pedigerous somite, genital double-somite and anal somite, together representing 14–15% of total body length. Relative lengths of urosomites (fifth pedigerous, genital double and free anal somites) 33.8: 38.4–45.0: 23–27.8 = 100, respectively ( Figs. 26 E, F, 30D–F). Lateral margins of fifth pedigerous somite weakly produced laterally, with or without wrinkles. Genital double-somite longest of urosome, with smooth dorsal and ventral surfaces except for longitudinal wrinkles on lateral margins of posterior half of somite ( Fig. 26 E, F) and few transverse wrinkles on the posterior half of same somite ( Fig. 30 D, F). Anterior half of somite moderately swollen; antero-ventral surface of somite moderately expanded ( Figs. 27 B, 30E). Ovigerous spines paired, separated at base, broken in specimen from sta. 34. Spines slender, about 38–45% of total body length, straight at their base and along shaft, distally tapering into acute points ( Fig. 28 E, F). Anal somite without medial constriction ( Figs. 26 E, F, 30D–F). Caudal rami weakly divergent, subrectangular, about 1.3 times as long as wide, armed with three caudal setae.

Antennule length 0.32–0.36 mm, representing about 21.0–21.5% of total body length and 29–35% of cephalothorax length, 4-segmented. Relative length of distal antennulary segment 44.8–50 %. In terms of pattern described by Grygier & Ohtsuka (1995) for female monstrilloid antennulary armature, short, curved spiniform element 1 present on first segment; elements on second segment: 2d1-2, 2v 1-3, and IId; element 2v 2 longest of group. Third segment with elements 3, IIId and IIIv of normal aspect. Segment 4 bearing elements 4d1,2, 4v 1-2, element 4v 3 not observed in any of the specimens examined; elements of this group equally long. Setae IVd, IVv, Vd, Vv, Vm, and element 4aes present. Element 5 absent. Subterminal elements b1-3, 5 present, slender, unbranched. Elements 61-2 and 6 aes present ( Figs. 27 A, 30A).

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 articulating with large, rectangular coxa along oblique line; with hair-like lateral seta ( Figs. 27 D–F, 29A–D); on leg 3, this seta about 2–3 times longer, thicker than those on other legs ( Figs. 27 F, arrowed in Fig. 29 C). 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 at base, bilobate, outer lobe cylindrical, distally truncate and moderately expanded distally. Inner lobe thumb-shaped, noticeably shorter than outer lobe, unarmed, arising proximally from exopodal lobe and reaching about half its length ( Figs. 26 F, 28C, 30D, 31D, E). Exopodal lobe armed with three distal setae, innermost seta slightly shorter than the other two.

Male. Not present in the samples examined, described by Desai & Krishnaswamy (1962) from the type locality, Mumbai ( Bombay Harbour), India.

Type locality. Mumbay Harbour, India.

New localities. Queenscliff, Victoria and Davies Reef, Queensland, Australia.

Remarks. The specimens from Australia (Queenscliff, Victoria and Davies Reef, Queensland) were identified as C. bali , a species originally described from off the Bombay Harbour by Desai & Krishnaswamy (1962). The species has not been observed since its original description and additional morphological data are presented in this contribution. The Australian specimens share with C. bali the structure and armature of the fifth leg, similar body proportions with the cephalic area narrower than the post-oral region, the same shape of the fifth pedigerous and genital double-somite, and even a remarkably protuberant oral papilla (see Desai & Krishnaswamy 1962: figs 1, 2). They also share a slender antennule and despite the fact that the original description lacks several details of the armature, the proportional length of the fourth antennulary segment and the size of the discernible setal elements ( Desai & Krishnaswamy 1962: fig. 6) support the notion that the Australian and the Indian specimens belong to the same species.

The fifth leg of this species, with its inner lobe weakly developed, represented by a low rounded protuberance arising from the middle margin of the outer lobe, resembles that of the Australian C. rafaelmartinezi sp. nov., but also C. reticulatum , C. striifrons , and partially to C. thompsonii . It has some morphological resemblance with C. alvaroi Suárez-Morales & Carrillo, 2013 ( Suárez-Morales et al. 2013a), both share similar body proportions, a reduced inner lobe on the female fifth leg and a relatively long genital double-somite. The conspicuous frontal process in C. alvaroi ( Suárez-Morales et al. 2013a: fig. 6A) is useful to easily separate it from C. bali , in which such process is absent.

The body proportions of C. bali both from Bombay and Australia differ from the Australian C. rafaelmartinezi , which has a long, slender cephalothorax and poorly pigmented eyes, thus diverging from the moderately elongate body and strongly pigmented eyes present in C. bali . The specimens from Davies Reef and Queenscliff show some subtle differences including the presence, in the specimens from the latter station, of a pair of minute papilla-like processes on the ventral surface between the nipple-like processes and the oral area ( Fig. 31 A, B); these are absent in the specimen collected at Davies Reef. Also, the three specimens of C. bali from Queenscliff lack the few dorsal wrinkles on the cephalic surface described for the specimen from Davies Reef. Otherwise, these two groups of specimens are identical and are thus deemed to represent the same species.

Based on the resemblance of this species with the illustrated record of females of C. thompsonii from Australia ( Dakin & Colefax 1940: fig. 205Ea–c), with the same body proportions (including the shape of the fifth pedigerous and genital double-somite, fifth leg structure and armature, plus the same length of the ovigerous spines as in C. bali (Desai & Krishnaswamy 1962: fig. 1)), it is suggested that Dakin & Colefax’s (1940) record of C. thompsonii is assignable to C. bali . The finding of this species in Australian waters represents the first record of this species after its original description more than 50 years ago and means an important range extension of its known distribution.

Figures

FIGURE 26. Cymbasoma bali Desai & Krishnaswamy, 1962, adult female, specimen A. A) habitus, lateral view; B) same, dorsal view; C) cephalic region, dorsal view; D) same, ventral view; E) urosome, dorsal view; F) same, ventral view showing fifth legs. Scale bars: A, B = 200 µm, C – F = 100 µm.

FIGURE 27. Cymbasoma bali Desai & Krishnaswamy, 1962, adult female, specimen A. A) left antennule, dorsal view; B) urosome, lateral view; C) cephalic region, lateral view; D) first leg; E) second leg; F) third leg. Scale bars: A = 50 µm, B – F = 100 µm.

FIGURE 28. Cymbasoma bali Desai & Krishnaswamy, 1962, adult female, specimen B. A) habitus, dorsal view; B) cephalic region, ventral view; C) urosome, lateral view; D) same, lateral view, specimen C; E, F) distal section of ovigerous spines of two different individuals (B and C). Scale bars: A = 200 µm, B – F = 100 µm.

FIGURE 29. Cymbasoma bali Desai & Krishnaswamy, 1962, adult female, specimen B. A) first leg; B) second leg; C) third leg; D) fourth leg. Scale bars: A – D = 100 µm.

FIGURE 30. Cymbasoma bali Desai & Krishnaswamy, 1962, adult females, specimens B and C. A) left antennule, specimen B; B) cephalic region, lateral view; C) same of specimen C; D) urosome and fifth legs, ventral view, specimen C; E) same, lateral view; F) same, dorsal view. Scale bars: A – F = 100 µm.

FIGURE 31. Cymbasoma bali Desai & Krishnaswamy, 1962, adult female. A) cephalic region, ventral view, specimen D; B) same, specimen C; C) cephalic region, lateral view, specimen D; D) urosome and fifth legs, ventral view, specimen A; E) same, specimen C. Scale bars: A – E = 100 µm.