Diogenes pallescens Whitelegge, 1897

Rahayu, Dwi Listyo & Osawa, Masayuki, 2012, Hermit crabs (Crustacea: Decapoda: Diogenidae) from the KUMEJIMA 2009 Expedition, Japan *, Zootaxa 3367 (1), pp. 176-190 : 183-185

Diogenes pallescens Whitelegge, 1897

( Figs. 1D , 2 )

Diogenes pallescens Whitelegge, 1897: 141 , pl. 6, figs. 2, 2 a–c. — Forest, 1956: 531. — Lewinsohn, 1969: 46. — Ball & Haig, 1972: 89, fig. 2. — Morgan, 1987: 176. — Rahayu, 1994: 83; 1996: 435; 2000: 391. — Rahayu & Forest, 1995: 413. — McLaughlin, 2002c: 91, figs. 1–3.

Diogenes gardineri Alcock, 1905a: 830 , pl. 68, fig. 1; 1905b: 73, pl. 7, fig. 3. — Forest, 1956: 530, fig. 16. — Lewinsohn, 1969: 45. — Ball & Haig, 1972: 91. — Nakasone, 1975: 3. — Gherardi & McLaughlin, 1994: 643. — McLaughlin & Haig, 1996: 123. — Rahayu & Forest, 1995: 410. — McLaughlin & Clark, 1997: 33. — Rahayu, 2000: 390.

Diogenes senex Bouvier, 1892: 55 . — Nobili, 1906a: 78; 1906b: 118. — Balss, 1927: 224. [not Diogenes senex Heller, 1865 ]

Diogenes serenei Forest, 1956: 530 , figs. 12–15. — Lewinsohn, 1969: 45. — Ball & Haig, 1972: 91. — Nakasone, 1975: 3. — Morgan, 1987: 178; 1989: 402; 1990: 19. — Haig & Ball, 1988: 168. — Gherardi & McLaughlin, 1994: 643. — Rahayu, 1994: 83; 2000: 391. — McLaughlin & Haig, 1996: 123. — Rahayu & Forest, 1995: 412. — Rahayu & Komai, 2000: 29. — McLaughlin, 2002b: 420, fig. 4A–C; 2002c: 88, figs. 2C, 3C, 4C, 5C.

Material examined. 2 males, 1.4 mm, Stn. Dredge 2, 26°23.147ʹN, 126°44.931ʹE, 9 November 2009, 70 m (RUMF-ZC-1646); 1 female 1.8 mm, 1 ovig. female 2.4 mm, Stn Dredge 44, 26°19.714ʹN, 126°45.649ʹE, 14 November 2009, 17.9–42.5 m ( NTOUA01222 ) ; 1 male 1.5 mm, Stn. Dredge 67, 26°19.940ʹN, 126°51.960ʹE, 18 November 2009, 6 m ( ZRC 2011.0728 ) .

Remarks. The material in this study agrees well with the redescription of the species by McLaughlin (2002c). McLaughlin (2002c) synonymized Diogenes gardineri Alcock, 1905 , and Diogenes serenei Forest, 1956 , to Diogenes pallescens and discussed at length the morphological variations of this species. The specimens examined have same intraspecific variations mentioned by McLaughlin (2002c) as follows: the length of the ocular peduncles is 0.70 to equaling of the shield length and shorter to slightly longer than the antennular peduncles; the intercalary rostral process is well developed, with or without prominent ventral spine; the meri of second pereopods are armed with one to five spines on the ventral margin; the carpi of the second pereopods are unarmed or have proximal spines on the dorsal margin.

The characters that McLaughlin (2002c) used to unify the three species mentioned above include the shape and armature of the telson: the possession of distinct median cleft and a row of small to large, posterior marginal spines which extend onto the lateral margins. In the five specimens from Kume Island, the telson lacks the median cleft, but has large marginal spines ( Fig. 1G ). Other differences detected are the presence of a row of spines on the ventromesial margin of the ischium of each cheliped and the presence of a prominent spine on the dorsal margin of each merus of the second pereopods ( Fig. 1C, F ). The ischia of the chelipeds and the dorsal margin of the meri of the second pereopods are unarmed in the material examined by McLaughlin (2002c). However, with regards to the character variability of this species, the five specimens examined from Kume Island are included in Diogenes pallescens . Another reason to include these specimens in Diogenes pallescens is the shape of the ocular peduncles which is prominently dilated proximally ( Fig. 1A ). It is very much like the figure of the specimen of Diogenes pallescens from Sek Island in New Guinea by Ball & Haig (1972, fig. 2a), although McLaughlin (2002c) mentioned and figured only the dilatation of corneas.

Colour. Carapace mottled brown and white; shield also with reddish-pink spot medially, and dark brown spot near each lateral margin. Ocular peduncles light brown proximally, dark brown ring present in transparent white distal area. Cheliped and ambulatory legs mottled white and brown.

Distribution. Indian Ocean from East Africa to Andaman Sea and northern Australia across Malay Archipelago ( Indonesia, Singapore and New Guinea) to Vietnam, Guam and Tuamotu Archipelago. And herein recorded from Kume Island in the Ryukyu Islands, 0– 42 m.

Figures

FIGURE 1. A, Dardanus brachyops Forest, 1962, female, 4.09 mm, Stn. Dredge 23; B, Diogenes holthuisi Asakura & Tachikawa, 2010, ovig. female 1.27 mm, Stn. Dredge 2; C, Diogenes leptocerus Forest, 1956, male, 2.4 mm, Stn. Intertidal 4 (right third pereopod missing); D, Diogenes pallescens, female ovig. 2.35 mm, Stn Dredge 44; E, Paguristes macrops Rahayu & Forest, 2009, male, 3.45 mm, Stn. Dredge 23 (left cheliped and right third pereopod missing); F, Pseudopaguristes laurentae Morgan & Forest, 1991, male, 2.54 mm, Stn. Dredge 78.

FIGURE 2. Diogenes pallescens Whitelegge, 1897, ovig. female 2.35 mm, Stn Dredge 44: A, shield, and ocular, antennular and antennal peduncles, dorsal view; B, left cheliped, outer view; C, merus of left cheliped, mesial view; D, distal segments of left fourth pereopod, lateral view; E, left third pereopod, lateral view; F, left second pereopod, lateral view; G, telson, dorsal view. Scales: A–C, E, F, = 1.0 mm; D, G = 0.5 mm.