Xiphonectes macrophthalmus ( Rathbun, 1906 )

Padate, Vinay P., Periasamy, Rengaiyan, Rivonker, Chandrashekher U. & Ingole, Baban S., 2023, Coral reef-associated brachyuran fauna (Crustacea: Decapoda: Brachyura) from Angria Bank off the west coast of India, Zootaxa 5357 (3), pp. 398-422 : 405-407

Xiphonectes macrophthalmus ( Rathbun, 1906)

( Fig. 4A–D )

Portunus (Xiphonectes) macrophthalmus Rathbun, 1906: 871 , pl. 12, fig. 5 (type locality: Modu Manu, Hawaii, Albatross station 4160, 31–39 fathoms (57–72 m) depth).— Rathbun 1911: 206.— Edmondson 1954: 242, figs. 18d–f, 19b.

Portunus macrophthalmus .— Stephenson & Rees 1967: 30.—Stephenson et al. 1968: 23.— Stephenson 1972b: 14 (key), 40.— Crosnier 2002: 410 .

Xiphonectes macrophthalmus .—Koch et al. 40 (list), tab. 1

Material examined. 1 female (6.0 × 2.9 mm) ( NIO /BOD/AB/BRY/00010), RVSS 10 , west of Vijaydurg , Arabian Sea, 16.62°N, 72.06°E, 42 m depth, Van Veen grab, coll. R. Periasamy, 8 January 2014 .

Diagnosis. Carapace slightly convex, frontal margin divided into 2 small submedian and 2 sharp, larger lateral teeth ( Fig. 4A, B ). Orbits deep, partially open, antennal flagellum lying in orbital hiatus ( Fig. 4C ). Mesogastric, cardiac and mesobranchial regions with short tubercles; anterolateral margins divided into 6 teeth, first 5 teeth acuminate and forward pointing, sixth tooth more than 4.0 × as long as preceding teeth and laterally directed ( Fig. 4A, B ). Posterolateral carapace margin forming angular junction with posterior margin ( Fig. 4B ). Maxilliped 3 merus triangular ( Fig. 4C ). Cheliped merus with 3 spines on anterior margin, 1 distal spine on posterior margin ( Fig. 4D ).

Colouration. Fresh specimen: carapace with two brown blotches on gastric regions which connect posteriorly in the cardiac region on white background, one red speck each on antero-lateral, postero-lateral and posterior margins.

Biology. Known to occur among corals, 42–101 m ( Rathbun 1906); 2–90 m ( Crosnier 2002). The present specimen was collected from sandy substratum at 42 m depth in the vicinity of corals.

Remarks. Rathbun (1906) originally described Portunus (Xiphonectes) macrophthalmus from Hawaii supplemented by a line illustration of the male pleon and a photograph of the dorsal habitus. Edmondson (1954: figs. 18d–f, 19b) provided a photograph and line illustrations X. macrophthalmus , and compared it with X. longispinosus ( Dana, 1852) . The Indian specimen conforms to the description provided by Rathbun (1906) and the identification key of Stephenson (1972b) in the presence of tubercles on the metagastric regions of the carapace, narrow frontal margin with median frontal teeth distinctly smaller than the laterals, anterolateral margin with 6 teeth and the last anterolateral tooth being distinctly longer than the preceding teeth.

Geographical distribution. Mauritius, Seychelles, Philippines and Hawaii (Stephenson 1972); eastern Arabian Sea off India (present study). The present observation is the first record from Indian waters.

Figures

FIGURE 4. Xiphonectes macrophthalmus (Rathbun, 1906), female (NIO/BOD/AB/BRY/00010, 6.0 × 2.9 mm), eastern Arabian Sea, India: (A) dorsal habitus (fresh colour); (B) carapace, dorsal view; (C) cephalothorax, ventral view; (D) right cheliped, dorsal view. Thalamita gatavakensis Nobili, 1906, male (NIO/BOD/AB/BRY/00011, 5.7 × 3.4 mm), eastern Arabian Sea, India: (E) dorsal habitus (fresh colour); (F) carapace, dorsal view; (G) cephalothorax, ventral view; (H) G1 distal portion, pleonal view. Scale bars: A–G, 1 mm, H, 0.5 mm.