Thalassograpsus harpax ( Hilgendorf, 1892 )

Naderloo, Reza, 2011, Grapsoid crabs (Decapoda: Brachyura: Thoracotremata) of the Persian Gulf and the Gulf of Oman, Zootaxa 3048, pp. 1-43 : 34-36

Thalassograpsus harpax ( Hilgendorf, 1892)

( Figs. 16 a–e, 18a–b)

Brachynotus harpax Hilgendorf, 1892: 38 . — Nobili 1906b: 320, 321.

Thalassograpsus harpax — Tweedie 1950: 134, figs. 4. — Guinot 1967: 286. — Hartnoll 1975: 307, 310, 317, 322 (lists). — Holthuis 1977: 169, 170. — Hogarth 1994: 105. — Davie & Ng 2007: 258, 259, figs.1, 2, 3. Ng et al. 2008: 227 (list).

Type Locality. Gulf of Aden.

Material examined. PERSIAN GULF, Iran: 1 female (ovig.) ( SMF 38446), rocky bed covered with algae, SW. of Qeshm, Qeshm I., 26º 33'N, 56º 15'E, coll. R. Naderloo, 15.02.2006; 2 males, 5 females (ovig.), 1 juv. ( SMF 38447), rocky bed, Shib-Deraz, Qeshm I., 26º 28'N, 56º 05'E, coll. R. Naderloo, 16.02.2006; 1 male, 1 female (ovig.) ( SMF 38448), rocky bed mixed with dead coral, Salakh, Qeshm I., 25º 41'N, 55º 53'E, coll. R. Naderloo, 17.02.2006; 6 males, 3 females (ovig.) ( SMF 48449), rocky bed/cobble mixed with dead coral, 10 km E. of Salakh, Qeshm I., 26º 40'N, 55º 44'E, coll. R. Naderloo & A. Kazemi, 11.05.2008; 2 males ( SMF 48450), stony getting muddy-sand in low-intertidal, NW. of Qeshm, Qeshm I., 26º 58'N, 56º 15'E, coll. R. Naderloo & A. Kazemi, 05.05.2008; 1 male, 1 female ( SMF 48451), rocky bed, Shib-Deraz, Qeshm I., 26º 41'N, 55º 55'E, coll. R. Naderloo & A. Kazemi, 11.05.2008; 1 female (ovig.) ( SMF 48452), rocky bed/cobble mixed with dead coral, 10 km E. Salakh, Qeshm I., 26º 40'N, 55º 44'E, coll. R. Naderloo & A. Kazemi, 11.05.2008; 2 females ( SMF 48453), patchy rocky bed, W. coast, Qeshm I., 26º 35'N, 55º 16'E, coll. R. Naderloo & A. Kazemi, 11.05.2008.

GULF OF ADEN, Djibouti: 1 female ( SMF 17272), eulitoral, Plage de Triton, coll. A. Allspach, G. Fischer & M. Türkay, 18.03.1987.

PACIFIC OCEAN, Japan: 1 male ( SMF 25991) Minato-gawa, Okinawa-Ken, Ryukyu Islands, coll. J. Kitaura, 12.07.1998.

Redescription. Carapace subquadrate ( Figs. 16 a, 18a), about 1.2 times as broad as long, maximum breadth between second anterolateral teeth; posterior surface smooth, small granules sparsely over posterior surface; anterior half of carapace moderately elevated; curved frontal ridges slightly elevated, granular. Front 2-lobed, lobes wide, slightly convex, separated by wide, deep median notch; frontal edge clearly longer than posterior edge of carapace. Inner orbital margins curved downward, completely separated from frontal lobes; elevated ridge extends obliquely from inner orbital margin towards frontal ridge; infraorbital margin with 3 interrupted lobes, median, lateral lobs granular; upper orbital margin is divided to 2 unequal lobes with hardly distinguishable fissure; margin of inner small lob smooth; margin of outer long lob obviously granular. Anterolateral margin with 3 teeth, first two of same size, large; last one smaller than formers; tip of teeth in large males quite blunt, white, in small specimens spiniform.

Third maxillipeds ( Fig. 16 d) with narrow gap between them, narrower in middle part; ischium smooth, about 3/ 2 as long as merus, narrowing proximally, inner margin elevated, long setae along inner margin; merus slightly broader than long, with prominently elevated margins, anterior margin nearly 2-lobed, inner lobe rounded, outer lobe nearly straight. Stridulating strip of males ( Fig. 16 c) with 4 parts: first one linear, regularly crenulated; second linear, massive, moderately rounded on anterior end, narrowing backwardly, reaching to anterior angle of first anterolateral tooth; third prominently rounded in anterior end, backwardly linear, reaching to anterior angle of second anterolateral tooth; fourth as large rounded tubercle. Stridulating strip of females linear, continuous, regularly crenulated, reaching to middle of first anterolateral tooth.

Chelipeds of males ( Fig. 16 b) large, usually subequal, smooth. Manus large, massive, as board as long; outer surface smooth, short row of small granulates longitudinally on other surface of unmovable finger; inner surface with patch of dense setae. Fingers slender, large gap between them, tips of fingers spooned, white-coloured; immovable finger curved upward distally, cutting edge without tooth; movable finger with large blunt tooth on middle point (in one of cheliped, left or right), variable amount of small teeth towards distal end.

Walking legs slender, flattened; merus with small distal spine on outer surface, fourth walking legs ( Fig. 16 e) with small distal spine on distal edge of carpus, dactylus with 4–6 distal spines on anterior surface, 1 or 2 median spines on posterior surface.

G1 ( Fig. 16 f) straight over most of its length, relatively stout, approximately diagonal in cross section, gently curved in the proximal part, distal part very slightly swollen, tip brown, narrow, directed outward, with distal margin concave, surrounded by long setae; genital opening distal ( Fig. 16 g).

Remarks. The examined material agrees well with the description of Thalassograpsus given by Tweedie (1950), particularly in the particular shape of the orbito-frontal margin. It also agrees with the original description of the species by Hilgendorf (1892), as well as the features highlighted by Davie and Ng (2007). Tweedie (1950) cited that the external maxillipeds meet completely in the middle line leaving no gap between them, as this is one of the characteristics of the genus. This feature was also described for the type specimen. Davie and Ng (2007) noted that this character distinguishes this from other three subfamilies of Varunidae . A distinct linear gap is seen in the present material from the Persian Gulf. Such a narrow gap was also observed in the specimens from Japan, but the illustration given by Sakai (1939: 675, fig. 119c) shows no gap, which may be an error. Nevertheless, this feature can be considered as characteristic of the subfamily and Thalassograpsus , as this gap is very distinct when compared with that of other varunid subfamilies.

Biology. This small-size species (largest male CL = 12.73 mm, CB = 15.04 mm, largest female CL = 9.11 mm CB = 10.92 mm) is primarily inhabitant of rocky shores, being found under small stones, dead corals and weedy habitats in shallow waters of the mid-intertidal. There is no information available on its life history.

Colour. Thalassograpsus harpax is variable in colour, which matches its habitats, with the upper surface of the carapace varying from dark brown with a varying form of pale flecks to pale colour with brown specks. Chelipeds and walking legs have the same colour pattern of the carapace. The ventral surfaces and abdomen is generally light coloured.

Regional records. PERSIAN GULF: Iran (present study). GULF OF OMAN: Oman ( Hogarth 1994).

Geographical distribution. Indo-West Pacific: Gulf of Aden, Oman (Dhofar), Persian Gulf, Cocos-Keeling Island, China, Taiwan, Philippines, Japan, Singapore, Australia, Samoa.

Figures

FIGURE 16. Thalassograpsus harpax (Hilgendorf, 1892), male (SMF 38447): a, posterior surface of carapace; b, cheliped of male, outer surface; c, lower orbital margin of male; d, third maxilliped (right); e, fourth walking leg of male (left); f, G 1, dorsal surface (left); g, apical part of same G 1.