Diogenes guttatus Henderson, 1888

Mclaughlin, Patsy A., 2004, A description of the first complete specimen of Diogenes guttatus Henderson, 1888 (Decapoda: Anomura: Paguroidea: Diogenidae), Zootaxa 466, pp. 1-8 : 2-7

Diogenes guttatus Henderson, 1888 ( Figs. 1 , 2 )

Diogenes guttatus Henderson, 1888: 54 , pl. 6, fig. 4, 4a; Alcock, 1905: 166 (list); Gordan, 1956: 317 (lit.); Morgan & Forest, 1991: 664; McLaughlin, 2002b: 411, fig. 1A, B; Siddiqui & McLaughlin, 2003: 961, fig. 4.

Not Diogenes guttatus . – Tirmizi & Siddiqui, 1981: fig. 17; Tirmizi & Siddiqui, 1982: 57, figs. 30, 31 (= Diogenes tirmiziae Siddiqui & McLaughlin, 2003 ).

Material examined. Queensland, Australia. Holotype male (sl = 3.2 mm), Challenger station 187, off Cape York, 10°36’S, 141°55’E, 11 m, 9 Sep 1874 (NHM 1888.33.1); 1 female (sl = 2.7 mm), off Thursday Island, 10°35’S, 142°13’E (AM P 67380).

Redescription. Shield ( Fig. 1 A) slightly broader than long, weakly convex; central dorsal surface smooth or with scattered tiny spinules; lateral marginal areas generally unarmed or with numerous small spines and spinules, each also with protuberant spinulose ridge in proximal half. Rostrum obsolete; lateral projections prominently produced, each with 1or more terminal spines or spinules. Dorsal margins of branchiostegites each with 5 or 6 acute spines. Intercalary rostriform process simple, tapering to acute tip, not reaching to apices of acicular spines.

Ocular peduncles 0.8 to almost full length of shield, dorsal surfaces each with or without row of sparse setae; corneal diameter 0.2–0.3 peduncular length; ocular acicles with 2– 5 spines on distal margin, innermost longest.

Antennular peduncles overreaching distal corneal margins by 0.8 to entire length of ultimate segments; ultimate and penultimate segments each with few scattered, long setae; basal segments each with row of small spines on distolateral margin, continued onto ventrodistal margin.

Antennal peduncles overreaching distal corneal margins by 0.4–0.6 length of ultimate segments; fifth segments each with 2 rows of long setae on ventral margin; fourth and third segments each with few scattered long setae; second segments each with dorsolateral distal angle produced into small to prominent spine, dorsomesial distal angle unarmed or with small spine, distolateral margin with row of spines ventrally, continued onto ventrodistal margin; first segments each with row of spines on distolateral margin ventrally, continued on ventrodistal margin. Antennal acicle short, broad, generally subquadrate, outermost spine reaching to or beyond midlength of penultimate peduncular segment, anterior margin with 2 or 3 additional prominent spines. Antennal flagellum shorter than twice carapace length, articles each with pair of long ventral setae.

Left cheliped ( Fig. 2 A) with slight to prominent hiatus between dactyl and fixed finger. Dactyl equal to length of palm or slightly shorter; with row of small to moderately large spines on upper margin, adjacent shorter row of smaller spines weakly to well developed; outer surface with numerous spinules and flattened tubercles; inner surface with scattered, moderately short setae; cutting edge with row of small, calcareous teeth; dactyl overlapping fixed finger in holotype, but overlapped by fixed finger in female. Palm with irregular single to double row of small to moderately large spines on upper margin; convex outer surface with covering of circular, mushroom­shaped, flattened tubercles and few spinules, often tear­drop in shape, lower margin with row of spines, 3 moderately stout, short (holotype) or several moderate to very prominent spines (female) near lower proximal angle, continued on proximal marginal as weak (holotype) or prominent (female) row of spines curving onto outer face; inner face with scattered low protuberances. Carpus with irregular single or double row of small to moderately large spines on upper margin, outer surface with covering of spinules, denser in lower half, lower margin with 2–5 small to large spines distally, lower surface with numerous spinulose tubercles, distal margin with row of very small, tuberculate spinules; inner surface with scattered spinules. Merus with row of spinulose protuberances and long setae on dorsal margin; mesial face with scattered spinules dorsally and tuberculate spines ventrally, ventromesial margin with irregular row of tuberculate spines; lateral face with scattered spinules, ventrolateral margin with irregular double row of spines; ventral surface with scattered small spines and spinules. Ischium with short row of small tubercles on laterodistal margin ventrally; ventromesial margin with few tubercles.

Right cheliped ( Fig. 2 B) appreciably shorter than left; with prominent hiatus between dactyl and fixed finger. Dactyl approximately 1.5 length of palm, distinctly overlapped by fixed finger; upper margin with 2 irregular rows of quite small spines; outer surface with irregular row of small spines and few additional scattered spinules; inner face with double row of small spines in proximal 0.6, not extending to tip; ventral surface unarmed; cutting edge with row of small calcareous teeth; all surfaces with moderately abundant, sparse tufts of long setae, not concealing armature. Palm slightly more than 0.5 length of carpus; upper margin with irregular double row of small spines; outer face with scattered small spines and spinules accompanied by sparse tufts of long setae; lower margin with row of small spines; inner face also with scattered spinules and setae. Carpus with irregular double row of small spines on upper margin partially obscured by long setae; outer face with weakly defined row of small spines and additional scattered spinules accompanied by sparse tufts of long setae; lower margin with few spinulose protuberances; inner surface also with scattered spinules, mesiodistal margin with row of small spines, extending onto lower distal margin as row of smaller spinules. Merus with row of low protuberances and tufts of long setae on dorsal margin; ventromesial margin with row of small spines and tufts of long setae; lateral face with few spinules in ventral 0.5, ventrolateral margin not distinctly delimited but with few spinules in proximal 0.5. Ischium with row of small spinules on ventromesial margin not concealed by sparse tufts of long setae.

Second ( Fig. 1 B, C) and third pereopods with dactyls slightly to distinctly curved, longer than propodi; all surfaces, mesial faces particularly, with moderately long setae.

Propodi unarmed but with setae dorsally and ventrally. Carpi of second pereopods each with row of quite small spines on dorsal margin; carpi of third pereopods each with row of very small spinules on dorsal margin. Meri each with low protuberances and setae on dorsal surface, ventral margins with fewer setae. Ischia unarmed, but with setae dorsally and ventrally. Sternite of third pereopods ( Fig. 1 D) generally subquadrate, with median tuft of setae on either side of midline.

Female with paired gonopores; unpaired left pleopods biramous; second with endopod 2­segmented, exopod incompletely 3­segmented; third and fourth with endopods also 2­ segmented, exopods incompletely 5­segmented; fifth pleopod with endopod vestigial, exopod incompletely 5­segmented.

Telson with small median cleft; left lobe of holotype ( Fig. 1 E) with 4 moderately large spines on terminal margin, 1more elongate spine at outer angle and 4 large spines on posterior 0.5 of lateral margin; right lobe with 3 small and 3 larger spines on terminal margin, outer 2 actually on rounded outer angle. Telson of female ( Fig. 1 F) with row of small and large spines on terminal margin of left lobe extending nearly full length of lateral margin; right lobe with several small spines accompanied by few larger spines on terminal margin, reaching only onto rounded proximal angle.

Coloration. Unknown.

Habitat. Unknown.

Distribution. Off Cape York Peninsula, Queensland, Australia; off Phuket, Thailand, Andaman Sea; 11– 61 m.

Remarks. As indicated in the redescription, D. guttatus , like several other species of the genus is subject to appreciable morphological variation in the strength of the armature of the chelipeds (e.g., Forest & Guinot 1956, Rahayu & Forest 1995, McLaughlin 2002a). Whether the differences seen in this armature of the left cheliped between the female from off Thursday Island and the holotype indicates sexual dimorphism cannot be determined at present. Given the relatively similar sizes of the two specimens, neither can it be ruled out. The female reported here is considerably larger than either the male or female Thai specimens reported by McLaughlin (2002b). Nonetheless, there is general agreement on the armature of the right chelipeds among those three specimens.

In spination of the pereopodal carpi, the female from off Thursday Island, like the holotype, has a row of spines or spinules on each pereopodal carpus, although they are slightly smaller in the female. This is in contrast to the two or three spines and few spinules reported by McLaughlin (2002b) for the Thai specimens. However, as demonstrated by Rahayu & Forest (1995) and Siddiqui & McLaughlin (2003), variations in carpal spination are not uncommon, even between right and left or second and third pereopods of individuals from a single locality. The telsons described for the Thai specimens appear to be intermediate in spination between the holotype and the female from off Thursday Island, but both Thai representatives are very similar to the Australian female in the spines of the ocular and antennal acicles.

McLaughlin (2002b) remarked on the very distinctive antennal acicles seen in both D. guttatus and D. tirmiziae . The two species are also similar in the armature of the right cheliped; however, as pointed out by both McLaughlin (2002b) and Siddiqui & McLaughlin (2003), D. tirmiziae can be differentiated by the presence of a row of spines on dorsal margin of each propodus and ventral margin of each merus of the second pereopods. Additionally, although McLaughlin did not describe the basal segments of the antennular peduncles of the Thai specimens, she did note the row of spines on the lateral margin of the second segment of each antennal peduncle. Siddiqui & McLaughlin (2003) described this margin in D. tirmiziae as having only three to five spines. At present, the mushroomshaped tubercles of the palm of the left cheliped of D. guttatus distinguish this species from all others in the genus. Considering the similarities seen between the female of D. guttatus from off Thursday Island and the two Thai specimens, there can be little doubt that all are conspecific.

Siddiqui & McLaughlin (2003) also discussed the similarities between D. tirmiziae , D. guttatus and D. dorotheae Morgan & Forest 1991 . The latter species is known only from its unique and quite small holotype, collected west of Cape Bossut, northern Western Australia. Morgan & Forest (1991) distinguished D. dorotheae from D. guttatus by the mushroom­shaped tubercles of the latter’s left chela. Diogenes dorotheae shares with the holotype of D. guttatus the prominent spines at the lower proximal angle of the left palm, and with the Australian female, the general armature of the telson. However, Morgan & Forest (1991) described the basal segment of the antennular peduncle as being unarmed. This segment in D. guttatus is provided with a distolateral row of spines that continues uninterruptedly onto the ventrodistal margin.

Figures

FIGURE 1. Diogenes guttatus Henderson, 1888, A – D, F, female, sl = 2.7 mm, off Thursday Island (AM 67380); E, male, holotype sl = 3.1 mm, Challenger stn 187 (NHM 1888.33.1). A, shield and cephalic appendages (aesthetascs omitted); B, right second pereopod (lateral view); C, dactyl of right second pereopod (mesial view); D, anterior lobe of sternite of third pereopods; E, F, telson (E after Siddiqui & McLaughlin, 2003). Scales equal 1 mm.

FIGURE 2. Diogenes guttatus Henderson, 1888, female, sl = 2.7 mm, off Thursday Island (AM 67380). A, chela and carpus of left cheliped (outer face); B, chela and carpus of right cheliped (outer face). Scale equals 1 mm.