Cymbasoma rafaelmartinezi, 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 : 21-24

Cymbasoma rafaelmartinezi sp. nov.

( Figs 11 , 12 )

Material examined. Holotype: adult female from near Warneet (Station R of Kimmerer & McKinnon, 1985), Western Port Bay, Victoria, Australia (38°26.792’ S, 145°18.496’ E), dissected, ethanol-preserved; dissected parts mounted on slides in glycerine, sealed with Entellan®. Date of collection: 9th March 1984. Slides deposited in the collection of MTQ, Australia (cat. MTQ W34376).

Description of adult female. Body noticeably elongate, slender; body length of holotype female 1.88 mm. Cephalothorax approximately 1.31 mm long, representing 68% of total body length. Midventral oral papilla moderately protuberant, located at 25% of cephalothorax length. Pair of relatively large ocelli present, pigment cups moderately developed, medially conjoined, intensely pigmented at inner margins only; ventral cup larger than lateral cups ( Fig. 11 B). Cephalic area with weakly produced "forehead”, ornamented with pattern of transverse striations ( Figs 11 B, C) with no frontal sensilla. Ventral surface with 1) pair of symmetrical nipple-like processes on anterior ventral surface; 2) papilla-like single sensilla on middle position between nipple-like processes and oral area ( Fig. 11 B); 3) low rounded protuberance anterior to oral papilla; 4) reduced field of light transverse striations surrounding oral area.

Urosome consisting of fifth pedigerous somite, genital double-somite and anal somite, together representing 12.7% of total body length. Relative lengths of urosomites (fifth pedigerous, genital double and free anal somites) 13.3: 50: 36.7 = 100, respectively ( Fig. 11 F). Genital double-somite longest of urosome, with smooth ventral surface, dorso-lateral surface with few longitudinal striae ( Fig. 11 E, F); anterior half of somite with two rounded lateral expansions, proximalmost smaller, distalmost somewhat angulate. Ovigerous spines paired, relatively short, basally separated, slender, straight at their base and along shaft, broken off proximally in examined specimen. Anal somite with medial constriction visible in dorsal and ventral views ( Figs 11 D, F, 12A). Caudal ramus subrectangular, 1.3 times longer than wide, armed with three subequally long, sparsely setulated caudal setae, broken off from proximal part in specimen examined.

Antennule length 0.40 mm, representing about 20 % of total body length and 30% of cephalothorax length; 4- segmented. Only one (left) antennule present in examined specimen, other one (right) broken off at first segment ( Fig. 11 A). Relative length of distal antennulary segment 45.7% of antennulary length. 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 element 3 being short, spiniform, elements IIId and IIIv of normal aspect. Segment 4 bearing elements 4d1,2, 4v 1-2, element 4v 3 not observed; elements IVd, Vd and 4aes present. Element 5 spiniform, strong, curved. Subterminal elements b1- 4, 6 present; elements b1-3 long, unbranched. Apical elements 61 and 6aes present in specimen ( Fig. 12 B).

Incorporated first pedigerous somite and succeeding three free pedigerous somites each bearing a pair of biramous legs. Pedigerous somites 2–4, together accounting for 19% of total body length. Legs 1–4 partly damaged. Intercoxal sclerites of legs 1–4 subrectangular, surface with patches of minute spinules, posterior margin smooth ( Fig. 12 E). Bases of legs articulating with large, rectangular coxae along oblique line; on legs 2–3 with hair-like lateral seta, but not found on leg 1 and 3 (probably broken off). Endopods and exopods of legs 1–4 triarticulated except for leg 4 with 2-segmented exopod bearing unusual armature including short outer spine and basally expanded setae ( Fig. 12 F, G) and one modified subdistal seta with bulbous process ( Fig. 12 G). Other 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, and sparsely setulated ( Fig. 12 C, D). Outermost apical exopodal setae of legs 1–4 with inner margin setulose, outer margin spinulose.

Armature formula of legs 1–4:

Fifth legs basally separated, represented by elongate, subrectangular outer lobe armed with three distal setae. Inner lobe represented by marginal notch of inner margin of outer lobe, unarmed, reaching about ¾ the length of outer lobe ( Figs 11 D, 12A).

Male: unknown.

Type locality. Station R of Kimmerer & McKinnon (1985), Western Port Bay, Victoria, Australia (38°26.792’ S, 145°18.496’ E).

Etymology. The species name is dedicated to Prof. Rafael Martínez, former teacher of Biology at El Colegio del Tepeyac, who inspired the first author’s (ES-M) early interest in natural sciences.

Diagnosis. Cymbasoma with long cephalothorax, representing 68% of total body length, third antennulary segment representing more than 45% of antennule length, with ventral protuberance on cephalic area between antennule bases and oral papilla. Genital double-somite with small proximal and larger medial protuberances. Anal somite with medial constriction. Fourth leg with short, 2-segmented exopod and modified, dwarfed distal setae (this diagnostic character should be confirmed in other specimens of this species). Fifth leg with elongate, subrectangular outer lobe with three distal setae, inner lobe represented by weak inner expansion of outer lobe, unarmed.

Remarks. This species has a remarkably elongate, slender cephalothorax which represents almost 70% of the total body length. This character is shared with only a few other species of the genus including some species of the C. longispinosum -group, like C. chelemense (cf. Suárez-Morales & Escamilla 1997) and C. morii Sekiguchi, 1982 (cf. Grygier 1994), but also C. frondipes ( Isaac, 1975) , C. gigas Scott, 1909 (cf. Suárez-Morales 2001c), C. gracile and C. reticulatum (cf. Giesbrecht, 1893). It differs from species of the C. longispinosum species-group by the presence of ovigerous spines that are separate at their bases as opposed to proximally fused spines as is always the case in this group. Also, the inner lobe is usually well defined in all species of the longispinosum- group (see Üstün et al. 2014).

The fifth leg, with the inner lobe very weakly developed, represented by a marginal expansion of the outer lobe, is similar to that of C. reticulatum , C. bali Desai & Krishnaswamy, 1962 , and C. striifrons Chang, 2012 . In two of these species the three setae of the fifth leg outer lobe are equally long and wide ( Giesbrecht 1893; Desai & Krishnaswamy 1962: fig. 10), whereas the innermost seta is shortest in C. striifrons ( Chang 2012) . In C. bali the exopodal setae of the fifth leg are subapical ( Desai & Krishnaswamy 1962) and they are apically inserted in the new species. In addition, the body proportions are different in C. bali and the new species. In addition, C. reticulatum can readily be distinguished among other species of the genus by its reticulated cephalosome and antennules, a character absent in the new species. Also, the shape of the genital double-somite is different in these species with that of C. reticulatum , C. bali , and C. striifrons having the lateral margins moderately produced, rounded ( Giesbrecht 1893; Desai & Krishnaswamy 1962; Chang 2012), whereas in the new species the anterior half has two lateral processes (see Fig. 11 E) and the posterior half has straight margins. The dorsal surface bears striae in both C. striifrons ( Chang 2012) and the new species. The most striking character of C. rafaelmartinezi sp. nov. is the 2-segmented exopodal ramus of the third leg, which is usually three-segmented in monstrilloids; and with distinctive armature comprising a short, naked apical spiniform seta in contrast to the usual very long setulated or spinulated seta; one subdistal seta is modified, with its proximal half forming two linear lobes and the distal half being whip-like and spinulate. This kind of modified seta has not been described in any other species of the genus.

Figures

FIGURE 11. Cymbasoma rafaelmartinezi sp. nov., adult female. A) habitus, lateral view; B) cephalic area showing cuticular ornamentation, ventral view; C) same, dorsal view; D) urosome, semi-lateral view; E) detail of lateral margin of genital doublesomite; F) urosome, dorsal view. Scale bars: A = 500 µm, B – F = 100 µm.

FIGURE 12. Cymbasoma rafaelmartinezi sp. nov., adult female. A) urosome showing fifth legs, ventral view; B) right antennule, dorsal view; C) second leg, endopodal ramus; D) first leg, exopodal ramus; E) fourth leg, endopodal ramus; F) fourth leg, showing bi-segmented exopodal ramus and modified, dwarfed setal elements (arrowed); G) fourth leg, detail of distal exopodal segment. Scale bars: A – F = 100 µm, G = 50 µm.