Diogenes avarus Heller, 1865

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 : 340-342

Diogenes avarus Heller, 1865

( Fig. 8A )

Diogenes avarus Heller, 1865: 83 , pl. 7, fig. 2 (type locality: Nicobar Island); Alcock, 1905b: 68, pl. 6, figs. 6‒6a; Forest, 1956a: 524, figs. 1‒4; Rahayu & Forest, 1995: 398, fig. 2b, g, h; Rahayu, 1996: 340; McLaughlin & Clark, 1997: 39, figs. 3b, 8b, 9b‒d; McLaughlin & Dworschak, 2001: 143, figs. 9‒12; McLaughlin, 2002a: 416, fig. 3A‒C; Siddiqui, Kazmi & McLaughlin, 2004: 191, fig. 16.

Diogenes rectimanus ‒ Lanchester, 1902: 366 (in part) (not Diogenes rectimanus Miers, 1884 ).

Diogenes pugilator ‒ Bouvier, 1892: 55; Nobili, 1903: 16; 1906a: 76 (not Diogenes pugilator Roux, 1829 ).

Material examined. 4 males, 1.0‒2.0 mm, 5 ovigerous females, 2.0– 2.5 mm ( ZRC 2021.0175 ), st. SW53, Seringat Kias, artificial lagoon, 1°13.630′N 103°51.218′E, hand collecting, sandy beach, seagrass, 24 May 2013 ; 1 male, 2.2 mm ( ZRC 2021.0176 ), Sungai Loyang, River mouth of Pasir Ris Park , 25 May 2012 ; 3 males, 2.2–3.6 mm ( ZRC 2021.0177 ), Seletar, Yishun avenue, 8 January 2012 ; 7 males, 1.1–2.7 mm, 6 ovigerous females, 1.45–2.4 mm ( MZB Cru 5212), st. MF63, Pulau Senang , 1°10.469′N 103°44.183′E, 30 June 2012 ; 15 males, 1.6–3.4 mm, 5 ovigerous females, 2.2–2.9 mm ( MZB Cru 5213), st. MF29, Seletar, North shore of Yishun Avenue 1, 13 August 2011 ; 8 males, 2.2–3.5 mm, 3 females, 2.7–3.5 mm, 5 ovigerous females, 2.0–4.0 mm ( ZRC 2021.0178 ), st. IT87, Pulau Semakau , 01°12.480′N 103°45.333′E, intertidal, 27 May 2013 ; 1 male, 2.9 mm, 2 ovigerous females, 2.2–2.5 mm, st. M24, Pulau Ketam , mudflat, 8 March 2012 ; 3 males, 1.8–2.7 mm, 1 ovigerous female, 2.00 mm ( ZRC 2021.0179 ), st. MF54, St John’s Island , 01°13.298′N 103°50.903′E, mudflat, 13 April 2012 ; 2 males, 1.1–1.6 mm, 1 ovigerous female, 1.6 mm ( MZB Cru 5211), st. SW101, Pasir Ris, Sungei Tampines River mouth, 01°22.910′N 103°57.232′E, 27 October 2012 ; 2 males, 1.5 mm, st. DW39, off Pulau Ubin, 01°23.608′N 103°58.355′E, 22–24 m, 19 October 2012; 2 ovigerous females, 2.2–2.4 mm ( ZRC 2021.0180 ), st. SW117, 01°23.619′N 103°59.441′E, 5‒9.9 m, 29 October 2012 ; 16 males, 0.8–1.7 mm, 1 female, 1.3 mm, 8 ovigerous females, 1.0– 2.5 mm ( ZRC 2021.0181 ), st. DW40, 01°23.797′N 103°58.751′E, Changi , 15‒26 m, 19 October 2012 ; 1 male, 3.4 mm ( ZRC 2021.0182 ), st. D22, Pulau Ubin , 8 March 2012 ; 2 males, 3.3– 2.5 mm, st. IT124, Terumbu Pampang Laut, 1°13.912′N 103°43.402′E, 30 May 2013; 3 ovigerous females, 2.00 mm ( ZRC 2021.0183 ), Chek Jawa, Pulau Ubin , 21 September 2001 ; 6 males, 2.2–3.8 mm ( ZRC 2021.0184 ), st. MF24, Tuas , 6 July 2011 ; 8 males, 1.4–2.5 mm, 3 ovigerous females, 1.8 mm ( ZRC 2021.0185 ), st. SW75, St John’s Island , 25 May 2013 ; 3 males, 2.4–3.1 mm, 4 ovigerous females, 2.0–2.5 ( ZRC 2021.0186 ), Kranji Reservoir Park , 01°26.90′N 103°16.26′E, 5 July 2009 ; 1 male (sl 2.4 mm), st. MF26, off Pulau Pergam , 19 July 2011 ; 1 male, 2.5 mm ( ZRC 2021.0187 ), st. SW10, Pulau Ubin, Sungei Besar, 01°25.151′N 103°57.196′E, 16 October 2012 ; 1 male, 2.2 mm ( ZRC 2021.0188 ), Sungei Jurong, along Jalan Papan , 19 August 2011 ; 14 males, 1.6–3.1 mm, 10 ovigerous females, 1.8–2.2 mm ( ZRC 2021.0189 ), Changi , 18 January 1995 ; 6 males, 1.4–2.9 mm, 1 female, 2.4 mm ( ZRC 2021.0190 ), st. MF40, Pulau Semakau , 10 November 2011 ; 1 male, 2.9 mm, st. MF9, Pulau Ubin , 13 May 2011 ; 20 males, 2.0– 3.3 mm, 1 female, 2.2 mm ( ZRC 2021.0191 ), st. MF52, Changi creek , 12 April 2012 ; 1 male, 2.7 mm ( ZRC 2021.0192 ), st. IT120, Pulau Hantu , 30 May 2011 ; 1 male, 2.2 mm, st. MF59, Sungei Loyang , 25 May 2012 ; 1 male, 3.3 mm ( ZRC 2021.0193 ), st. MF48, Sarimbun Beach, 01°26.279′N 103°41.915′S, 14 February 2012 ; 2 males, 2.4 mm ( MZB Cru 5214), Sentosa beach, 16 July 2010 ; 1 male, 2 mm, 1 ovigerous female, 1.6 mm ( ZRC 2021.0194 ), st. IT101, St John’s Island , 29 May 2013 ; 7 males, 1.8–2.2 mm, 6 ovigerous females, 1.5–1.8 mm ( MZB Cru 5210), MF38, Pulau Ubin , 26 September 2011 ; 7 males, 1.8–3.3 mm, 1 ovigerous female, 2.4 mm ( ZRC 2021.0195 ), Pulau Semakau , 11 September 2010 ; 1 male, 1.3 mm, st. DW120, Johor Strait, 20.6‒21.4 m, 29 October 2012 ; 7 males, 1.8–3.1 mm, 1 ovigerous female, 2.2 mm ( ZRC 2021.0196 ), Pulau Semakau , 31 July 2010 and 11 Sepetember 2010.

Colour. Shield mottled light and dark yellowish brown; ocular peduncles white with greenish brown speckled medially, yellowish brown band proximally and distally adjacent to corneas, cornea dark brown; chelipeds light brownish yellow, white on dactyl, fixed finger, and lateroventral surface of palm; P2 and P3 light brown, dactyls white, propodus with transverse brown band medially, carpi and meri mottled with light and dark brown ( Fig. 8A ).

Distribution. From Red Sea, East Africa across Indian Ocean to Malaysia, Thailand, Singapore, Indonesia, and Australia; intertidal, inhabit sandy, mud substrate.

Remarks. Thanks to the redescription by McLaughlin & Dworschak (2001), the diagnostic characters of D. avarus are clarified. Those include: relatively short ocular peduncle, about 0.6 times as long as shield with the corneal diameter 0.4 times as long as the ocular peduncle; the presence of proximo-medially weak crest of spines or tubercles (not continuing to the articulation with the dactyl) on the outer surface of the palm of the left cheliped; the presence of row(s) of spines on the dorsal margin of the propodus and carpus of P2; similar row of spines usually, but not always, on the dorsal margin of the propodus and carpus of P3; and a noticeable hiatus between fingers of the right cheliped.

Most of the specimens examined in this study have dorsally unarmed propodi of P2 and P3; the carpi of P2 and P3 bear a row of spines on each dorsal margin, although the spines are smaller and fewer on the P3. The ocular peduncles also vary from stout (0.7 times as long as the shield with the corneal diameter 0.2 times as long as the ocular peduncle) to slender (0.9 times as long as the shield with the corneal diameter 0.3 times as long as the ocular peduncle). Nevertheless, the specimens from Singapore agreee well with D. avarus in other diagnostic characters cited above ( McLaughlin & Dworschak, 2001).

Figures

Fig. 8. A, Diogenes avarus Heller, 1852, not collected, IT86, Cyrene Reef, 1°15.374′N 103°44.816′E, 27 May 2013; B, Diogenes fasciatus Rahayu & Forest, 1995, male, 5.3 mm (ZRC 2021.0132); C, Diogenes klaasi Rahayu & Forest, 1995, male, not collected, Singapore Strait; D, Diogenes laevicarpus Rahayu, 1996, male, 5.1 mm (ZRC 2021.0139); E, Diogenes moosai Rahayu & Forest, 1995, male, 1.8 mm (ZRC 2021.0160); F, Diogenes rectimanus Miers, 1884, male, not collected, DW58, East of Pulau Tekong, 01°25.064′N 104°04.992′E, 10.9–11.3 m, 22 October 2012.