Diogenes jubatus ( Nobili, 1903 )

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 : 335-337

Diogenes jubatus ( Nobili, 1903)

( Figs. 5A‒C , 6A , 7A, B )

Troglopagurus jubatus Nobili, 1903: 17 (type locality: Singapore).

Diogenes jubatus Forest, 1952: 9 ; Lemaitre & Ng, 1996: 324, figs. 1–5; Rahayu, 1996: 344; McLaughlin, 2005: 601, 612, figs. 3, 4a–c.

Material examined. 1 male, 5.1 mm ( ZRC 2021.0114 ), st. TB99, Eastern Bunkering A, 1°18.861′N 104°05.128′E, silt, 33.7–36.7 m, 28 May 2013 ; 1 male, 5.5 mm, 1 female, 5.5 mm ( MZB Cru 5200), st. TB58, Around Tanah Merah , 1°16.808′N 103°58.246′E, mud, 38.7−39.9 m, 24 May 2013 ; 2 males, 1.1–3.1 mm ( MZB Cru 5201), st. SW27, along seawall at south lagoon of St John’s Island, 1°12.911′N 103°51.718′E, 0.5 m, 22 May 2013 ; 1 ovigerous female, 2.2 mm, 1 female, 2 mm ( ZRC 2021.0115 ), st. SB55, Kusu Island , 1°13.9′N, 103°52′E, 4 m, 24 May 2013 ; 1 male, 1.5 mm, 1 female, 1.8 mm ( ZRC 2021.0116 ), no locality ; 1 female, 2.4 mm ( ZRC 2021.0115 ), st. TB113, South of Sisters’ Island, 1°12.001′N 103°50.261′E, rock, 29.3–30.5 m, 29 May 2013 .

Diagnosis. Shield ( Figs. 5A , 7A, B ) as long as broad or very slightly broader than long, with few short tubercles and tufts of setae on dorsal surface; dorsal surfaces of branchiostegites unarmed or with few minute or miniscule spinules. Rostrum short, triangular, reaching level of lateral projections. Intercalary rostriform process vestigial or reaching proximal 0.20 of ocular acicles. Ocular peduncles 0.7–0.8 times as long as shield, delated proximally, slightly tapering to cornea, with tufts of sparse setae on dorsal surface proximally; corneal diameter 0.2 times as long as ocular peduncle; ocular acicles each with 3–5 spines. Antennular peduncle overreaching distal corneal margin by entire length of ultimate segment. Antennal peduncle stout, reaching midlength of ultimate segment of antennular peduncle, reaching beyond distal corneal margin by 0.25 to entire length of fifth peduncular segment; antennal acicle reatively broad, short, not reaching half length of fourth segment, with 8–9 spines on oblique or truncate inner margin; flagellum with very long setae, primarily inserted ventrally. Left cheliped dactyl ( Figs. 6A , 7A, B ) with rows of strong spines on upper margin, and few granules, tubercles or spinules on outer surface; palm upper margin with tubercles or spines, lower margin with row of tubercles or spines continuing onto fixed finger, outer face with scattered small spines or tubercles; long plumose setae covering dactyl and palm entirely, concealing armature, those setae extending on inner face near upper and lower margin; carpus with numerous tufts of setae, but not concealing armature, upper margin with row of acute or subacute spines, outer face with scattered spinules or spines, distal margin usually with row of spines. Right cheliped with chela completely masked by setae; dactyl usually with row of small spines or spinules on upper margin; palm and fixed finger unarmed; carpus with prominent spine on upper distal margin and one or two somewhat smaller spines on outer distal margin. P2 and P3 ( Figs. 6A , 7A, B ) with dactyls equal to 1.5 times as long as propodi, unarmed, except for small dorsodistal spine on each carpus and occasionally few tubercles or spinules on ventral margins of meri of P2; left P3 covered entirely with dense setae, while left P2, right P2 and P3 with less dense setae. Sternite of third pereopods (thoracic sternite 6) subquadrate ( Fig. 5B ), anterior lobe subsemicircular with median longitudinal depression, armed with spinules and/or with central tubercle(s) on either side of median depression. Telson ( Fig. 5C ) with left posterior lobe strongly produced, right very short, terminal margins each with series of small to moderately large spines, strongest at outer angles and on left extending onto lateral margin.

Colour in life. Shield generally cream, mottled with brown and dark brown, setae white. Ocular peduncles dark brown or black with white streak proximally and distally, corneas black. Antennular peduncle penultimate segment cream with black streak proximally, ultimate segment and flagella cream. Antennal peduncle first to fourth segments and antennal acicle brown, fifth segments and flagella cream. Cheliped mottled with cream and dark brown; P2 and P3 generally cream, with brown band on each segment ( Fig. 7A, B ).

Distribution. Malaysia and Singapore; at 0.5–39.9 m depth, on substrates consisting of mixture of rock, gravel, mud, and sandy mud.

Remarks. See Remarks section of Diogenes platyops for the taxonomic clarification.

Lemaitre & Ng (1996) described the colour of the dark parts of this species as “black”, but in the newly collected specimens the dark parts are attributed as dark brown. The colour pattern is quite consistent between the present specimens and those described by Lemaitre & Ng (1996).

Figures

Fig. 5. A–C, Diogenes jubatus (Nobili, 1903), male, 5.1 mm (ZRC 2021.0114); D–F, Diogenes platyops Rahayu & Forest, 1995, male, 4.9 mm (ZRC 2021.0118); G–I, Diogenes jousseaumei (Bouvier, 1897), ovigerous female, 5.8 mm (ZRC 2021.0128). A, D, G, shield and cephalic appendages; B, E, H, anterior lobe of sternite of third pereopods; C, F, I, telson. Scale = 1 mm.

Fig. 6. A, Diogenes jubatus (Nobili, 1903), male, 5.1 mm (ZRC 2021.0114); B, Diogenes platyops Rahayu & Forest, 1995, male, 4.9 mm (ZRC 2021.0118). A, B, left cheliped, P2 and P3.

Fig. 7. A, B, Diogenes jubatus (Nobili, 1903); A, ovigerous female, not collected, Johor Strait, 21 October 2012; B, male, 5.1 mm (ZRC 2021.0114); C, D,Diogenes platyops Rahayu & Forest, 1995; C, male (not collected), st. TB29, Singapore Strait,01°13.036′N 103°52.820′E, 22 May 2013; D, ovigerous female, 3.5 mm (ZRC 2021.0125); E, Diogenes jousseaumei (Bouvier, 1897), male, 2.2 mm (ZRC 2021.0129).