Diogenes pallescens Whitelegge, 1897

Rahayu, Dwi Listyo, 2022, Hermit crabs of Singapore (Crustacea: Decapoda: Anomura: Diogenidae, Paguridae), with description of two new species, Raffles Bulletin of Zoology 70, pp. 329-363 : 349

Diogenes pallescens Whitelegge, 1897

( Fig. 9C )

Diogenes pallescens Whitelegge, 1897: 141 , pl. 6, figs. 2, 2a–c (type locality: Funafuti, Ellise Islands); Ball & Haig, 1972: 89, fig. 2; Morgan, 1987b: 176; Rahayu, 1996: 435; McLaughlin, 2002a: 91, figs. 1–3; Rahayu & Osawa, 2012: 183, fig. 2.

Diogenes gardineri Alcock, 1905a: 830 , pl. 68, fig. 1 (type locality: Maldives); 1905b: 73, pl. 7, fig. 3; Forest, 1956a: 530, fig. 16.

Diogenes senex – Bouvier, 1892: 55; Nobili, 1906a: 78; 1906b: 118; Balss, 1927: 224 (not Diogenes senex Heller, 1865 ).

Diogenes serenei Forest, 1956a: 530 , figs. 12–15 (type locality: Vietnam); McLaughlin, 2002a: 420, fig. 4A–C; 2002b: 88, figs. 2C, 3C, 4C, 5C.

Material examined. 4 males, 1.6–3.8 mm, 2 females, 2.0– 2.7 mm ( ZRC 2021.0204 ), Pulau Jong , 7 m, 21 December 2012 ; 1 male, 1.6 mm, 1 female, 2.0 mm ( ZRC 2021.0205 ), Pulau Semakau , 21 December 2012 ; 1 male, 2.0 mm ( ZRC 2021.0206 ), Pulau Hantu , 23 March 2013 ; 17 males, 2.5–3.6 mm, 3 females, 1.8–3.6 mm, 2 ovigerous females, 4.4–4.7 mm ( MZB Cru 5216), st. SD40, West P. Semakau, 1°12.389′N 103°45.24′E, dive, 7.5 m, 23 May 2013 ; 4 males, 1.8–3.1 mm, 1 ovigerous female, 3.5 mm ( ZRC 2021.0207 ), st. SD45, Channel between Lazarus and St John’s Island, dive, 16.2 m, 23 May 2013 ; 4 males, 1.6–2.2 mm ( ZRC 2021.0208 ), st. IT65, Terumbu Semakau, 1°12.649′N 103°46.199′E, hand collecting, 0–0.5 m, 24 May 2013 ; 1 ovigerous female, 2.5 mm ( ZRC 2021.0209 ), st. IT80, Terumbu Bemban , intertidal, 28 May 2013 ; 1 male, 2.7 mm ( ZRC 2021.0210 ), st. IT87, Pulau Semakau , intertidal, 27 May 2013 ; 1 male, 2.2 mm, 1 female, 2.4 mm ( ZRC 2021.0211 ), st. IT124, Terumbu Pempang Laut, 01°13.912′N 103°43.402′E, submerged reef, 30 May 2013 ; 1 male, 2.5 mm ( ZRC 2021.0212 ), st. IT140, Tekukor, 1°13.899′N 103°50.265′E, intertidal, 31 May 2013 ; 2 males, 2.2–3.1 mm, 1 female, 1.6 mm, 7 ovigerous females, 2.4–3.6 mm ( ZRC 2021.0167 ), st. SD143, east of Pulau Hantu , 10 m, 31 May 2013 ; 1 male, 3.6 mm, 3 ovigerous females, 1.3–1.8 mm ( ZRC 2021.0213 ), st. SD150, Kusu Island , dive, 10.7 m, 1 June 2013 ; 1 male, 1.5 mm, 1 female, 2.2 mm ( ZRC 2021.0214 ), st. SB152, P. Kusu, 01°13.274′N 103°51.659′E, dive, 3 June 2013 ; 1 male, 3.3 mm, 1 female, 2 mm ( ZRC 2021.0215 ), st. SW155, St John’s Island , 01°13.116′N 103°51.079′E, 3 June 2013 ; 1 male, 3.6 mm, 1 ovigerous female, 1.6 mm, 1 ovigerous female, 3.1 mm ( ZRC 2021.0216 ), st. SD167, P. Jong , dive, 15.4 m, 4 June 2013 ; 1 ovigerous female, 2.2 mm ( ZRC 2021.0217 ), SD179, Terumbu Raya, 01°12.750′N 103°44.983′E, coral reef, dive, 5 June 2013 ; 1 male, 1.6 mm, Pulau Hantu, dive, 7–10 m, 16 December 2012; 1 female, 2.0 mm ( ZRC 2021.0218 ), MF64, Pulau Pawai, 01°11.088′N 103°43.683′E, 1 July 2012 .

Colour in life. Shield mottled with light and dark brown, and white; ocular peduncles with brown ring subdistally, reticulated pattern of light brown on dorsal surface. Chelipeds and ambulatory legs cream mottled with dark and light brown; submedian black spot on dorsal margins of propodi, carpi, and meri of ambulatory legs ( Fig. 9C ).

Distribution. Widely distributed in the Indo-West Pacific; 0–10 m, occurring in intertidal to subtidal muddy-sand and gravel substrates.

Remarks. Among the species of the Diogenes pallescens group, D. pallescens is easily recognised by the long, slender ocular peduncles with a distinct brown subdistal ring and irregular reticulated pattern of brown, the convex outer surface of the palm of the left cheliped with row of strong spines on the midline, and the presence of a row of spines on the ventral margin of the P2 merus.

Figures

Fig. 9. A, B, Diogenes inglei McLaughlin & Clark, 1997, ovigerous female, 1.8 mm (ZRC 2021.0201); C, Diogenes pallescens Whitelegge, 1897, male, not collected, st. SD40, West P. Semakau, 1°12.389′N 103°45.24′E, 23 May 2013; D, Diogenes tumidus Rahayu & Forest, 1995, male, not collected, SW53, Seringat Kias, artificial lagoon, 1°13.630′N 103°51.218′E, 24 May 2013.