Ilyograpsus rhizophorae Barnard 1955

Ilyograpsus rhizophorae Barnard, 1955

(Figs. 1, 2 a–j, 3a, b)

Ilyograpsus rhizophorae Barnard 1955: 26, fig. 8. — Kensley 1981: 46 (in list). — Sawada et al. 2005: 862. — Komai & Wada 2008: 361, figs. 2–5.

Ilyograpsus paludicola — Crosnier 1965: 31–33, figs. 36–37, 38 a–b, 39, 59. — Fishelson 1971: 128. — Basson et al. 1977: 228, 234. — Titgen 1982: 254 (in list). — Jones 1986: 160, pl. 46. — Vousden 1987: tab. 4. — Ismail & Ahmed 1993: 158. — Hywel-Davies 1994: 37, 48. — Apel 1996: 331 (in list). — Al-Ghais & Cooper 1996: 415. — Tirmizi & Ghani 1996: 143, fig. 55. — Hornby 1997: 14. — Apel & Türkay 1999: 132. — Apel 2001: 117 [not Ilyograpsus paludicola Rathbun, 1909].

Ilyograpsus vanninii — Sawada et al. 2005: 853 (part), fig. 5b, d, f.

Type locality. Inhambane, Mozambique (East Africa).

Examined material. Persian Gulf (Iran): 2 females (1 ovig.), 2 juv. (ZUTC brach1265) Qeshm I., S. coast, 26º 43'N, 55º 49'E, sandy flat with patch of dead corals, 0 9.01.2008, R. Naderloo & M. Türkay; 2 males (ZUTC brach1262), Qeshm I., N coast, 3 km W. of Kuweii, 26º 57'N, 56º 00'E, muddy flat, 13.01.2008, R. Naderloo & M. Türkay; 3 males, 9 females (6 ovig.) (ZUTC brach1261), Qeshm I., 2 km E. of desalination centre, 26º 56'N, 55º 47'E, muddy sand with shells, 15.12.2008, R. Naderloo & M. Türkay; 1 female (ovig.) (ZUTC brach1263), 15 km E. of Bandar-Deylam, behind Boyrat police station, 29º 56'N, 50º 08'E, muddy flat, 23.05.2008, R. Naderloo, A. Kazemi & H. Salehi; 3 females (ZUTC brach1264), Qeshm I., Dargahan, 26º 58'N, 56º 04'E, sandy mud-flat, with planted mangroves, 13.01.2008, R. Naderloo & M. Türkay; 1 female (SMF 36856), Qeshm I., Zeyton (olive) park beach, 27º 11'N, 56º 24'E, rocky with dead corals, 0 8.01.2008, R. Naderloo & M. Türkay; 1 male (SMF 36857), Bandar-Khamir, E. fishery Jetty, 26º 56'N, 55º 36'E, muddy flat, water channel, 24.04.2008, R. Naderloo, A. Kazemi, & A. Keykhosravi; 2 females (ovig.) (SMF 36858), Bandar-Emam, Park Saheli, 30º 28'N, 49º 04'E, muddy flat with artificial rocky structure covered with Saccostrea sp., 20.05.2008, R. Naderloo, A. Kazemi & H. Salehi; 2 males, 3 females (SMF 36859), Khalij-Nayband, mangroves, 27º 23'N, 52º 39'E, muddy substrate, 0 5.01.2005, R. Naderloo & A. Kazemi; 2 males, 1 female (SMF 36860), Bandar-Khamir, E. fishery Jetty, 26º 56'N, 55º 36'E, sandy mud-flat, 0 7.06.2006, R. Naderloo & A. Kazemi; 1 male (SMF 36861), Bandar-Khamir, E. of City, behind mangroves, 26º 28'N, 55º 35'E, muddy substrate, 31.12.2005, R. Naderloo, A. Kazemi.

Gulf of Oman: (Iran): 3 females (SMF 36862), Khor-Khalasi, 25º 35'N, 58º 02'E, mangroves, muddy substrate among trees, 20.11.2005, R. Naderloo & A. Kazemi.

Comparative material. Ilyograpsus rhizophorae Barnard 1955: 1 male, 2 female (NHM 1984:416), Pakistan, Manora I. mangroves, Karachi, 0 4.03.1982, N.M. Tirmizi & N. Ghani. Ilyograpsus paludicola Rathbun, 1909: 1 male, 2 females (ZRC 1998.1030), Indonesia, Pulau Bintan, P.K.L. Ng & C.G.S. Tan, June.1995, det. T. Komai.

Redescription. Carapace nearly subquadrate (Figs. 1, 3 a), slightly wider than long (CL/CB = 1.18), maximum width between third lateral teeth; posterior surface uneven, relatively convex, regions poorly defined; 2 transverse ridges on frontal region, smooth, straight; without epigastric ridges; several transverse ridges on posterolateral region, short, oblique. Front relatively broad, about 0.4 times as wide as carapace, broadly bi-lobed, lobes slightly extending beyond inner orbital angle. Anterolateral margin with 4 distinct teeth, first (exorbital angle) largest, acute, wide triangular, directed forwards; second blunt, as long as first, slightly higher than latter; insetting between first, third teeth; third acute, triangular, highest among all teeth; fourth very small, acute; posterolateral margin nearly subparallel, converging posteriorly (Fig. 1).

Eyestalks moderately long, orbit slightly more than one fourth of maximum carapace width, upper orbital margin slightly sinuous; lower orbital margin of males (Fig. 2 a) with 3, 4 long tubercles; lower orbital margin of females (Fig. 2 b) with numerous denticles, irregular, variously-sized, larger laterally.

Third maxilliped (Fig. 2 f) with moderately large gap; ischium about 1.5 times as long as merus, with wide elevation near inner margin, short setae scarce along inner margin; merus short, much shorter than wide, with relatively narrow elevation near inner margin, short setae scarce on inner margin; exopod proximally wide, narrowing distally.

Chelipeds relatively small; upper margin of merus minutely serrated, with small subdistal spine; lower inner margin finely serrated proximally, distally denticulated, slightly expanded; lower outer margin denticulate; plectrum (Fig. 2 e) on inner surface near lower margin, distinct, short. Manus (Fig. 2 c) about 2.4 times as long as high, slightly longer than movable finger; outer surface smooth, very small, sparse granules on upper portion; lower margin concave in middle part; inner surface smooth, patch of dense setae on distal portion, extending to proximal part of fingers. Fingers relatively narrow, long, smooth, narrow gap between fingers, wider distally; long setae along inner, outer margins of cutting edge; movable finger with cutting edge slightly elevated proximally, with small, variously-size denticles; immovable finger with small denticles on cutting edge, large ones on middle portion; tip of fingers spoon-shaped. Cheliped of females (Fig. 2 d) narrow, long, about 3.2 times as long as high; merus with small subdistal spine on upper margin, stridulating ridge on inner surface; palm without patch of setae on inner surface; cutting edge of fingers scarcely with small denticles; gap between fingers becoming slightly wider distally.

Walking legs (Fig. 1) relatively long, moderately slender, flattened; second, third largest; merus with large subdistal spine, anterior margin sinuous, faintly serrate, posterior margin nearly straight, merus of fourth leg about 2.6–2.9 times as long as wide (around 2.0 in females); propodus with distal spine on posterior margin, fourth walking legs with short setae along anterior, posterior margins; dactylus narrow, long, unarmed.

Male abdomen (Fig. 2 g) moderately narrow, segments 4, 5 longest, of equal length; segment 6 about 1.75 as wide as long, lateral margin nearly straight on anterior half, converging posteriorly; telson longer than wide, slightly longer than segment 6, posteriorly rounded.

Male G1 (Figs. 2 i, j) narrow, straight, slightly curved mesially, apical process long, slightly bent laterally, with depression on lateral surface, distal opening distally on lateral surface; long setae along apical process, short setae scarce along lateral, ventral surface.

Female gonopore (Fig. 2 h) with elevated lateral lobe; operculum small, hinging on inner margin, directed outwards.

Remarks. Ilyograpsus paludicola (Rathbun, 1909) has been frequently recorded from the Persian Gulf (Basson et al. 1977; Titgen 1982; Jones 1986; Vousden 1987; Ismail & Ahmed 1993; Hywel-Davies 1994; Apel 1996; Al-Ghais & Cooper 1996; Tirmizi & Ghani 1996; Hornby 1997; Apel & Türkay 1999; Apel 2001). We collected a large number of specimens from the different sections of the Iranian coast of the Persian Gulf. Precise examination revealed that the Persian Gulf species clearly belongs to I. rhizophorae Barnard, 1955. Morphological differences between these two species as listed by Komai & Wada (2008) are all seen between the Persian Gulf specimens and specimens of I. paludicola (one male and one female, ZRC 1998.1030). In particular, the G1 of the present specimens has a terminal process that is narrow and long, curved laterally, resembling to that of I. rhizophorae. Persian Gulf specimens, however, are slightly different from I. rhizophorae from other regions regarding the length/width ratio of the merus of the fourth walking leg. In our specimens, this proportion in males is smaller than 3.00 (about 2.6–2.9) in males and about 2.00 in females, whereas the length/width merus ratio of the fourth leg of I. rhizophorae is about 3.48–3.84 in male and 2.52 in females (Komai & Wada 2008).

Komai & Wada (2008), in their revision of Ilyograpsus, did not record any specimens of I. rhizophorae from the Persian Gulf and did not refer to the numerous published records from the region (see above). Nevertheless, they mentioned that the species recorded from Pakistan (Tirmizi & Ghani 1996) is likely to be identical with I. paludicola. We examined material from Pakistan (one male and one female, NHM 1984:416) which is clearly I. rhizophorae. Ilyograpsus rhizophorae is thus widely distributed in the western Indian Ocean (Komai & Wada 2008) including the Red Sea, Gulf of Oman and the Persian Gulf, whereas I. paludicola occurs in eastern India and the western Pacific, including Thailand (type locality), Indonesia, Malaysia to Vietnam, Australia and New Caledonia, but does not extend into the western Indian Ocean.

Biology. Ilyograpsus rhizophorae is a small-size species (largest male CL = 4.92, CB = 5.60 mm, largest female CL = 9.65, CB = 11.64) usually found in the lower intertidal zone of muddy substrates. They are among the most common crabs in mangroves, occurring among trees and pneumatophores. In one case a male was found underneath the bark of a decaying trunk of the mangrove Avicennia marina. The carapace of I. rhizophorae is dirty white to whitish brown, with the appendages being slightly lighter than the carapace. There are irregular light brown bands on the legs, being more distinct on the distal part of carpus and propodus. The ventral surface of the carapace is lighter than the dorsal surface. Flores et al. (2003) described the first zoeal stage of I. paludicola from East Africa, but based on the present study and Komai & Wada (2008), their larvae can be attributed to I. rhizophorae.

Geographical distribution. Western Indian Ocean: Madagascar, Mozambique, East Africa, Gulf of Aden, Red Sea, Persian Gulf, Pakistan.