Rochinia paulayi, Ng, Peter K. L. & Forges, Bertrand Richer De, 2007

Ng, Peter K. L. & Forges, Bertrand Richer De, 2007, A new species of deep-water spider crab of the genus Rochinia A. Milne-Edwards, 1875, from Guam (Crustacea: Brachyura: Majidae), Zootaxa 1610, pp. 61-68 : 63-66

Rochinia paulayi , new species

Figs. 1 , 2

Material examined. Holotype, ovigerous female, 29.2 x 19.2 mm (37.2 mm wide including epibranchial spines) ( ZRC), deep-water, 1.5 miles off Merizo, Guam, Micronesia, coll. Pioneer, 3 October 1998.

Diagnosis. Relatively small size. Carapace pyriform; with 2 long, divergent, slightly curved pseudorostral spines (2/3 length of carapace); dorsal surface very spiny, with total of 17 acute spines in the following pattern: 2 long, curved preocular spines pointing upwards; 2 very long hepatic spines pointing outwards; 1 long mesogastric spine directed vertically; 2 pairs of protogastric spines, anterior pair smaller than posterior pair; 2 very long branchial spines; 2 smaller epibranchial spines; 3 cardiac spines (1 mesocardiac, 2 protocardiac); 1 intestinal spine ( Figs. 1 , 2 A, C). Eyes small, with round cornea ( Fig. 2 A). Orbit not well defined, with 1 postorbital cupped tooth ( Fig. 2 A). Antennule fossae long, sharp anteriorly; antennae short, merus fused to carapace, carpus, propodus cylindrical, antennal flagellum slender, short. Pterygostomian region elongated, smooth. Buccal frame quadrangular; outer surface of third maxilliped smooth, with short setae; ischium quadrate ( Fig. 2 B). Cheliped (female) much shorter than P2; merus short, triangular, with strong curved distal spine, with 2 large granules on upper and lower portions; carpus short, carinated on upper edge; propodus short, flattened; fingers of chelae slightly serrated ( Fig. 1 A, C). Ambulatory legs long, length decreasing from P2 to P5; P2 longest; articles of P3-P5 cylindrical, covered with thin tomentum; dactyli curved, sharp ( Fig. 1 A). Female abdomen ovate, domed, with 6 mobile somites, telson, each somite with large median tubercle ( Fig. 2 C).

Etymology. The species is named in honour of Gustav Paulay, whose surveys and collections on Guam have substantially increased our knowledge of the Micronesian fauna.

Discussion. Of the 24 other species of Rochinia sensu stricto known from the Indo-West Pacific region, only a few have very long spines on the carapace. The only species resembling R. paulayi , new species, are R. pulchra ( Miers, 1886) , R. riversandersoni ( Alcock, 1895) and R. griffini Davie & Short, 1989 .

Rochinia pulchra was described by Miers (1886) from the Challenger material from the Philippines. Compared to R. paulayi , it has relatively short spines. Griffin (1976) reported on this species again from the Philippines and subsequently from Indonesia ( Griffin & Tranter, 1986a). In R. pulchra there are four spines on the median line of the carapace but only three in R. paulayi . In R. pulchra only the two branchial spines are long whereas 15 spines are long in R. paulayi (see Miers, 1886; Griffin, 1976).

Rochinia riversandersoni was described by Alcock (1895) from the Investigator material from India. It is characterized by very long carapace spines. Griffin (1976) subsequently recorded it from the Philippines. Yaldwyn and Dawson (1976) also reported the species from the Kermadec Islands near New Zealand; their figures clearly showing that the fresh specimen is covered by a thick tomentum. Rochinia riversandersoni and R. paulayi , new species, are similar in adult size and both possess very long carapace spines. However, the two species are relatively easy to separate. In total, there are only 15 carapace spines in R. riversandersoni but 17 in R. paulayi . In R. riversandersoni the postorbital spine is continuous with the hepatic spine but in R. paulayi there is a large gap between these two spines. In R. paulayi , the long preocular spines are pointing upwards while in R. riversandersoni they are proportionately shorter and pointing anteriorly ( Griffin & Tranter 1986a; Yaldwyn & Dawson 1976). There are, however, indications that the New Zealand material identified as “ R. riversandersoni ” by Yaldwyn & Dawson (1976) may not be conspecific with Alcock’s (1895) specimens from the Indian Ocean (S. T. Ahyong), although they are very close.

Rochinia paulayi is perhaps most similar to R. griffini . Rochinia griffini was described by Davie and Short (1989) from the Iron Summer and Kapala cruises in the Coral Sea. Through the kindness of Shane Ahyong, we had the opportunity to compare R. paulayi with a good series of photographs of a female paratype of R. griffini in the Australian Museum (AM–P32090) ( Fig. 3 ). The total number of carapace spines is 15 in R. griffini versus 17 in R. paulayi ( Fig. 1 A vs. Fig. 3 A). There are two pairs of protogastric spines in R. paulayi but only one distinct pair in R. griffini . In R. griffini , there is actually a tubercle just anterior to each protogastric spine, but this is not developed into a spine like in R. paulayi . There is a low granular crest on the lower border of the subhepatic region in R. paulayi but there are two small granules at this location in R. griffini (cf. Davie & Short 1989: 176, fig. 11a). The preocular spines are prominently divergent in R. griffini ( Fig. 3 A, C) but are subparallel in R. paulayi ( Fig. 1 A, B); and the ischium of the third maxillipeds of R.

griffini are relatively more longitudinally rectangular ( Fig. 3 B) than that of R. paulayi which is more quadrate ( Fig. 2 B).

Figures

FIGURE 1. Rochinia paulayi, new species. Holotype, ovigerous female, 29.2 x 19.2 mm (ZRC). A, overall view; B, frontal view; C, lateral view.

FIGURE 2. Rochinia paulayi, new species. Holotype, ovigerous female, 29.2 x 19.2 mm (ZRC). A, lateral view showing orbits; B, third maxillipeds; C, posterior view of carapace.

FIGURE 3. Rochinia griffini Davie & Short, 1989. Paratype female, 56.2 x 42.0 mm (including spines) (AM – P 32090). A, overall carapace view; B, third maxillipeds; C, frontal view; D, lateral view. (courtesy S. T. Ahyong).