Charybdis granulata (de Haan, 1833 )

Ahyong, Shane T. & Lee, Timothy, 2005, Charybdis moretonensis Rees & Stephenson, 1966, a junior synonym of Charybdis granulata (de Haan, 1833) (Crustacea: Decapoda: Brachyura), Zootaxa 1089 (1089), pp. 57-63 : 58-61

Charybdis granulata (de Haan, 1833) ( Figs. 1, 2)

Portunus (Charybdis) granulatus de Haan, 1833 , pl. 1: 1, 1a [type locality: Japan].

Charybdis beauforti Leene & Buitendijk, 1949: 293 , figs. 2, 4b [type locality: Madras , India].

Charybdis moretonensis Rees & Stephenson, 1966: 37–39 , pl. 7D [type locality: Moreton Bay , Queensland, Australia] [new synonymy].

Charybdis (Charybdis) granulata .— Yamaguchi & Baba, 1993: 405–406, fig. 142.

Charybdis (Charybdis) moretonensis .— Davie, 2002: 474.

Charybdis granulata .— Poore, 2004: 424, figs. 135c, 137k.

Material examined. AUSTRALIA: AM P13081, 1 female (25.1 x 35+ mm) (holotype of Charybdis moretonensis ), 3 ½ miles S of Woody Point Pier, Moreton Bay, 7–10 m, trawled, E. M. Grant, 26 October 1952, (with Sacculina ); AM P53543, 1 female (22.9 x 31.8 mm), E of Clarence River, New South Wales, 29 20’S 153 27’E, 46 m, trawled, K95­ 06­52, FRV Kapala, K. Graham , 8 June 1995; AM P53540, 2 males (23.4 x 31.6 mm, 24.3 x 31.7 mm), 3 females (25.3 x 34.0 mm–42.2 x 59.8 mm), E. Brunswick Heads, New South Wales, 28 35’S 153 34’E, 15 m, trawled, K91­16­10, FRV Kapala, K. Graham , 10 November 1991; AM P41758, 1 male (52.7 x 74.3 mm), E of Brunswick Heads, New South Wales, 28 35’S 153 34’E, 15 m, trawled, K91­16­10, FRV Kapala, K. Graham , 10 November 1991; AM P60289, 4 males, (20.8 x 29.1 mm –42.1 x 59.2 mm), 1 ovigerous female, (41.5 x 60.6 mm), E of Clarence River, New South Wales, 29 23’S 153 23’E, 29 m, trawled, K96­06­30, FRV Kapala, K. Graham , 18 April 1996; AM P60474, 1 male (35.8 x 50.7 mm), E of Clarence River, New South Wales, 29 23’S 153 24’E, 31 m, trawled, K96­06­19, FRV Kapala, K. Graham , 29 May 1996; AM P60268, 1 male, (70.3 x 102.3 mm), E of Fitzroy Reef, Great Barrier Reef, Queensland, 23 32.46’S 152 16.45’E, 100 m, trawled, QLD­1076, 86.2 % sand, 13.0 % gravel, 0.8 % mud, MV Reefknot, J.K. Lowry & K. Dempsey, 2 June 1994; AM P60262, 1 male (74.0 x 106.3 mm), E. Fitzroy Reef, Queensland, 23 34.92’S 152 11.76’E, 50 m, trawled, QLD­951, MV Reefknot, J.K. Lowry & K. Dempsey, 16 June 1993; AM P70244, 1 female (40.5 x 57.2 mm), between Bradleys Head and Kirribilli, Port Jackson, 33°51.3’S, 151°14.0’E, 17–18 m, muddy sand, trawl, S. Ahyong, 24 February 2000.

JAPAN: ZRC ex2004.0646, 1 male (60.0 x 87.9 mm), Ishikawa, Okinawa Is., Ryukyus, coll. J.C.Y. Lai et al., 26 November 2003 .

TAIWAN: ZRC 1998.195 , 1 male (47.6 x 70.9 mm), 1 female (51.0 x 76.4 mm), Port at Tungkang, Kaohsiung County, SW Taiwan, shallow water inshore trawl, coll. P. Ng, 5 August 1996 ; ZRC 2004.0643 , 1 female (40.9 x 59.6 mm), Tai­Shi, I­Lan County, trawl, coll. J.C.Y. Lai & N.K. Ng, 1 December 2003 .

SINGAPORE: ZRC 1973.10 .30.32.34, 2 males (45.7 x 67.0 mm, 45.6 x 66.8 mm), Siglap, coll. M. Tweedie, July 1934 .

THAILAND: ZRC 2000.0051 , 2 males (64.8 x 92.5+ mm, 61.8 x 93.0 mm), Andaman Sea off Pichai, Phuket, P. Ng, December 1999 ; ZRC 1998.1131 , 2 males (27.8 x 39.4 mm –60.5 x 90.0 mm), 1 female (53.2 x 77.9 mm), Andaman Sea off Phuket fishing pier, S. Chiatiamvong et al., December 1998 ; ZRC 2000.0771 , 1 male (57.3 x 81.6 mm), 1 female (69.3 x 102.6 mm), Andaman Sea off Phuket fishing pier, N. K. Ng et al., 17–20 January 2000 .

Size range. Males (n = 19) 20.8 x 29.1 mm –74.0 x 106.3 mm, females (n = 11) 22.9 x 31.8 mm –69.3 x 102.6 mm. Smallest ovigerous female 41.5 x 60.6 mm.

Remarks. Rees & Stephenson (1966) distinguished Charybdis moretonensis from the two most similar species then recognised, namely C. granulata (as C. beauforti ) and C. natator , chiefly by the presence of one instead of three spines on the outer surface of the cheliped carpus. Re­examination of the holotype of C. moretonensis , however, revealed that Rees & Stephenson (1966) misinterpreted the spination of the cheliped carpus. The holotype of C. moretonensis is incomplete in lacking the left cheliped and left third ambulatory leg. On close examination of the cheliped carpus of the holotype of C. moretonensis , we found evidence of three spines, as in C. granulata . One spine is intact, and the other two are broken at their bases, accounting for the original observation of a single spine (compare Figs. 1C, 2F). Rees & Stephenson (1966: 39), however, also distinguished C. moretonensis from C. beauforti on the basis of:

1) the frontal teeth being more rounded;

2) granular patches mesially flanking the anterolateral border of the carapace;

3) a medially interrupted mesogastric ridge;

4) the presence of anterior mesobranchial ridges;

5) the presence of four instead of three spines on the anterior border of the cheliped merus. Comparison of the holotype of C. moretonensis with a large series of C. granulata from eastern Australia and various Indo­West Pacific localities showed that each of these aforementioned characters is unreliable as a distinguishing feature. The frontal marginal teeth of the carapace, whilst exhibiting a degree of individual variability, are similarly rounded in size­matched specimens, becoming narrower and more widely separated with increasing body size ( Figs. 1B, 2A, C). All specimens of C. granulata , had granular, anterolateral patches on the carapace, as in the holotype of C. moretonensis , although the granules may be concealed by the dorsal tomentum. In all specimens of C. granulata examined, the mesogastric ridge on the carapace is interrupted medially, and anterior mesobranchial ridges are present both of these features are in fact present in the types of C. beauforti (see Crosnier 1984: fig. 4D, E) but were incorrectly figured by Leene & Buitendijk (1949). Lastly, the number of spines on the anterior border of the cheliped merus is an unreliable feature distinguishing C. moretonensis from C. granulata because the number of spines increases with increasing size. The anterior margin of the cheliped merus bears a series of graded spines and acute tubercles, in which some of the tubercles become proportionally larger with increasing body size ( Figs. 1D, 2B, D). The spination of the cheliped merus in the holotype of C. moretonensis resembles that of size­matched specimens of C. granulata .

It is also noteworthy that the characters of the holotype of C. moretonensis recognised by Rees & Stephenson (1966) as distinguishing their species from C. natator , namely, the median frontal teeth being on a lower plane than the remainder, the more acute inner orbital angle, the generally sharper anterolateral carapace teeth, and the more numerous and more conspicuous carapace ridges, are all features that distinguish C. granulata from C. natator . The differences between the two species are fully discussed and illustrated by Wee & Ng (1995). No doubt, Rees & Stephenson (1966), as with Leene & Buitendijk (1949), were unfamiliar with the type material of C. granulata and thus had little reason to question its synonymy with C. natator .

Charybdis moretonensis is morphologically indistinguishable from C. granulata . The characters used by Rees & Stephenson (1966) to distinguish C. moretonensis as a new species were based on misinterpretation of the holotype (i.e., the number of carpal spines) and inaccuracy of the type account of C. beauforti . Moreover, the type locality of C. moretonensis is within the geographical range of C. granulata , adding further circumstantial support to the synonymy of the two nominal species. Therefore, C. moretonensis is herein synonymised with C. granulata .

The present series of C. granulata examined herein includes the largest known specimen of the species (male 74.0 x 106.3 mm, AM P60262). The eastern Australian specimens of C. granulata are the first to be formally reported from the region and extend the known range south to the Sydney area (Port Jackson). Poore (2004) reported C. granulata from Western Australia.

Habitat. Sandy or muddy substrates; shallow subtidal depths to at least 100 m.

Distribution. Japan (type locality), Taiwan, China, Singapore, Australia, the Andaman Sea and East Africa.