Sphaerodromia nux Alcock, 1900

Padate Sherine Sonia Cubelio Masatsune Takeda, Vinay P., 2021, Rare deep-water crabs (Crustacea: Decapoda) from Indian waters, with description of one new species, Nauplius (e 2021034) 29, pp. 1-21 : 6

Sphaerodromia nux Alcock, 1900

( Figs. 2D, E , 4 )

Sphaerodromia nux Alcock, 1900a: 154 (type locality: Gulf of Martaban). — Alcock, 1901: 40, 78, pl. 4, fig. 19. — Ihle, 1913: 92 (list). — Lewinsohn, 1984: 115, pl. 3, fig. B, pl. 4, figs. C–D. — McLay, 1991: 463, 465 (discussion), tab. 1 (comparison). — McLay and Crosnier, 1991: 186 (discussion). — McLay, 1993: 126 (list), 127 (key). — Crosnier, 1994: 347 (remarks). — McLay, 2001: 821 (key, description). — Guinot and Tavares, 2003: 107, 108, figs. 22B, 23A–B. — Ng et al., 2008: 36 (list). — Trivedi et al., 2018: 36 (tab. 1).

Material examined. 1 male (CL 29.3 mm, CW 33.1 mm) ( IO /SS/BRC/00295), west of South Andaman Island , Bay of Bengal, FORVSS stn. 349 (leg II) 09, 11.93°N 92.28°E, 290 m, coll. Dr. Aneesh Kumar K. V., HSDT ( CV), 12 April 2016 .

Remarks. Sphaerodromia nux was originally described from supposedly juvenile specimens (1 male of undetermined size, 1 female 10 × 11 mm) from the Gulf of Martaban off Myanmar at 129 m depth ( Alcock, 1900a). The original description by Alcock (1900a) described only the carapace, and a subsequent monograph by Alcock (1901) provided a short description of the third maxilliped, chelipeds, and the vestigial male pleopods on pleonal somites 3–5 supplemented with a line illustration of the dorsal habitus ( Alcock, 1901: fig. 19). Lewinsohn (1984) redescribed this species from adult specimens from Madagascar, and reported differences from the type specimen in the absence of a gap between the anterior margin of the third maxillipeds and the buccal cavern. McLay(1991)provided a detailed comparison between S. nux and Sphaerodromia ducoussoi McLay, 1991 , and supplemented with a table comparing the diagnostic morphological characters of all Sphaerodromia species. Crosnier (1994) commented that S. nux possessed well-developed podobranchs on the cheliped and pereopod 2, and vestigial bud-like podobranchs on pereopod 3. McLay (2001) amended Lewinsohn’s redescription and added morphological details of female specimens from the Philippines. A systematic revision of the family Dromiidae by Guinot and Tavares (2003) included illustrations of the vestigial male pleopods, P5 coxa and G2.

The present specimen agrees with the updated description by McLay (2001), except for the presence of lines of compressed granules on the P2–P3 meri ( Fig. 4F–G ) and a relatively higher dactylus length/ propodus length of 0.90 for P2–P3. The present observation is a new record in Indian waters.

Distribution. Gulf of Martaban at 129 m depth ( Alcock, 1900a; 1901), Madagascar ( Guinot and Tavares, 2003), and Andaman Sea, India at 290 m depth (present study).

Figures

Figure 2. A–C, Sphaerodromia kendalli (Alcock and Anderson, 1894), male (CL 38.6 mm, CW 45.4 mm) (IO/SS/BRC/00294), southwest Bay of Bengal, India. D,E, Sphaerodromia nux Alcock, 1899, male (CL 29.3 mm, CW 33.1 mm) (IO/SS/BRC/00295), Bayof Bengal west of South Andaman Island, India.A, D, dorsalhabitus; B,E, denuded dorsalcarapace; C, denuded lateral carapace. Scale bars: 10 mm.

Figure 4. Sphaerodromia nux Alcock, 1899, male (CL 29.3 mm, CW 33.1 mm) (IO/SS/BRC/00295), Bay of Bengal west of South Andaman Island, India. A, Antennule and antenna; B, third maxilliped; C, right chela and carpus, outer view; D, P2 merus, dorsal view; E, P2 dactylus, dorsal view; F, P2–P3 meri, ventral view; G, P3 dactylus, dorsal view; H, I, P4–P5 subchela, dorsal view; J, posterior pleonal somites and telson, ventralview; K, pleonal somites 3–5 and telson in dorsal view indicatingthe form and position of vestigial pleopods; L, M, G1 dorsal andventral views; N,O, G2 dorsal and ventralviews.Scale bars:B–C= 5mm,A, D–O= 2mm.