Portunus convexus De Haan, 1835

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

Portunus convexus De Haan, 1835

( Fig. 3H )

Portunus (Pontus) convexus De Haan, 1833: 9 (type locality: Japan).

Portunus (Pontus) Convexus. — Herklots 1861: 118.

Neptunus sieboldi A. Milne-Edwards, 1861: 323 , pl. XXXV fig. 5.— Henderson 1893: 370.

Neptunus convexus .—de Man 1883: 150.— Nobili 1901: 9.—de Man 1902: 643, pl. 21 figs. 27 a–b.— Nobili 1906a: 193–194.

Portunus convexus .— Crosnier 1962.—47, figs. 60, 64–66, 69–70, pl. 2, fig. 2.— Guinot 1962b: 10.— Stephenson 1972b: 13, 15 (identification key), 38.— Stephenson 1976: 16.— Vannini 1976: 122, 126.— Hogarth 1989: 104 (list).— Holthuis 1993: 614, Fig. 7.— Fransen et al. 1997: 108.— Apel & Spiridonov 1998: 284, figs. 96, 108.— Vannini & Innocenti 2000: 262, figs. 19, 24, 77.

Material examined. 1 juvenile (damaged specimen, not measured), ( NIO /BOD/AB/BRY/00009), RVSS 9 , west of Vijaydurg , Arabian Sea, 16.57°N, 72.10°E, 27 m depth, Van Veen grab, coll. R. Periasamy, 7 January 2014 .

Diagnosis. Carapace broader than long, frontal margin divided into 6 teeth (including inner supra-orbital angles); anterolateral margins divided into 9 acuminate teeth, ninth tooth longest and laterally directed; posterolateral junction rounded ( Fig. 5H ). Cheliped merus with 3 spines on anterior margin, dactylus as long as propodus ( Fig. 5H ).

Colouration. Fresh specimen: carapace frontal and orbital margins as well as first 4 antero-lateral teeth white, rest of the carapace brownish yellow, 2 pale spots outlined in brown on the postero-lateral portion ( Fig. 3H ).

Biology. Known to be an inhabitant of sandy substrata, rock pools, crevices ( Vannini & Innocenti 2000) and intertidal sea grass beds ( Crosnier 1962); 20–27 m ( Stephenson 1976; present study). The present specimen was collected from rocky substratum, at 27 m depth, covered with macroalgae.

Remarks. De Haan (1833) described Portunus convexus from Japan. Crosnier (1962) provided an illustrated description of this species from Madagascar. Apel & Spiridonov (1998) provided an illustrated description of material from Arabian Gulf supplemented with notes on habitat and geographical distribution. Vannini & Innocenti (2000) provided a brief illustrated description of Somalian specimens. The present specimen conforms to the description of the carapace being less than twice as wide as long by Crosnier (1962), and that of the live colouration ( Stephenson 1972b) in the presence of a pale subcircular spot outlined with brown near each posterolateral margins of carapace. Contrary to Vannini & Innocenti’s (2000) observation that this species does not occur in reefs, the present specimens were collected from a coral reef habitat.

Geographical distribution. East coast of Africa, Madagascar, Mascarenes, Persian Gulf, Sri Lanka, Indonesia, Japan ( Vannini & Innocenti 2000), Guam ( Paulay et al. 2003), French Polynesia ( Poupin et al. 2018); eastern Arabian Sea off India (present study). The present observation is the first record from Indian waters.

Figures

FIGURE 3. Tanaocheles bidentata (Nobili, 1901), male (NIO/BOD/AB/BRY/00007, 4.7 × 2.9 mm), eastern Arabian Sea, India: (A) carapace, dorsal view; (B) left maxilliped 3, external view; (C) right cheliped, dorsal view; (D) cephalothorax, ventral view; (E) G1, pleonal view. Cycloachelous granulatus granulatus (H. Milne Edwards, 1834), male (NIO/BOD/AB/BRY/00008, damaged specimen), eastern Arabian Sea, India: (F) dorsal habitus (fresh colour); (G) ventral habitus (fresh colour). Portunus convexus De Haan, 1835, juvenile (NIO/BOD/AB/BRY/00009, damaged specimen), eastern Arabian Sea, India: (H) dorsal habitus (fresh colour). Scale bars: A–E, 1 mm. F–H, 5 mm.

FIGURE 5. Trapezia tigrina Eydoux & Souleyet, 1842, 1 male,1 female (NIO/BOD/AB/BRY/00006, both damaged specimens), eastern Arabian Sea, India: (A) dorsal habitus of male (fresh colour); (B) ventral habitus of male (fresh colour); (C) dorsal habitus of female (fresh colour); (D) ventral habitus of female (fresh colour). Serenius ceylonicus (Laurie, 1906), male (NIO/ BOD/AB/BRY/00003, 5.9 × 4.1 mm), eastern Arabian Sea, India: (E) dorsal habitus (preserved colour); (F) ventral habitus (preserved colour); (G) right cheliped, dorsal view; (H) P5, dorsal view. Scale bars: A–D, 10 mm, E–H, 1 mm.