Oncopagurus minutus ( Henderson, 1896 (Henderson, 1896)

Lemaitre, R., 1996, Hermit crabs of the family Parapaguridae (Crustacea: Decapoda: Anomura) from Australia: species of Strobopagurus Lemaitre, 1989, Sympagurus Smith, 1883 and two new genera., Records of the Australian Museum 48 (2), pp. 163-221 : 201-204

Oncopagurus minutus ( Henderson, 1896 )

Fig. 21

Parapagurus minutus Henderson, 1896: 531 (type locality: off the north Maldive Atoll, Investigator, sta. 150, 719 fms (1308.6 m).- Alcock & Anderson, 1897, pI. 32, fig. 3, 3a.- Alcock, 1901: 222.-A1cock, 1905: 101, pI. 10, fig. 3.-De Saint Laurent, 1972: 108.

Sympagurus minutus .- Lemaitre, 1989: 37.- Lemaitre, 1994: 412.

?not Parapagurus minutus .- Thompson, 1943: 417 (See remarks under Oncopagurus indicus Alcock, 1905 ).

Type material. SYNTYPE, female (SL 2.3 mm), Indian Ocean, off north Maldive Atoll, Investigator , sta. 150, 719 fms (1308.6 m), NHM 1896:9.8.24.

Australian material. NEW SOUTH WALES: 1 male (SL 2.5 mm), NZOI Tangaroa , U222, off Newcastle, 1075- 1040 m, 9 Oct 1982, AM P40409.

Other material. INDONESIA: 1 male (SL 4.0 mm), Sulawesi (Celebes), Gulf of Tomini, off Limbe Is., Albatross sta. 5601, 01°13'10"N, 125°17'05"E, 1399 m, 13 Nov 1909, USNM 168943. 1 female (SL 2.2 mm), Siboga Exp. sta. 88, 00034.6' S, 119°08.5'E, 1301 m, 20 Jun 1899, colI. M. Weber, ZMA De103.112. 1 male (SL 2.0 mm), Moluccas, S of Patiente Strait, off Doworra Is., Albatross sta. 5631, 00057' S, 127°56'E, 1480 m, 2 Dec 1909, USNM 168944. 1 male (SL 3.5 mm), 1 female (SL 3.4 mm), Moluccas, Pitt Passage, off Gomomo Is., Albatross sta. 5636, 01°55'S, 127°42'30"E, 2308 m, 3 Dec 1909, USNM 168945. 2 males (SL 2.0, 2.6 mm), Celebes, Gulf of Boni, off Olang Point, Albatross sta. 5656, 03°17'40"S, 120036'45''E, 885 m, 19 Dec 1909, USNM 168946.

Diagnosis. Shield ( Fig. 21a ) as long as broad; dorsal surface weakly calcified medially; rostrum broadly rounded, with short, low dorsal ridge; anterior margins weakly concave; lateral projections subtriangular, terminating in small spine; ventrolateral margin with small spine (not always visible in dorsal view); posterior margin broadly rounded. Ocular peduncles more than half length of shield, diminishing in width distally, and with long setae dorsally; ocular acicles subtriangular, terminating in strong spine; corneae cone-shaped (Fig. 2Ia,b), maximum width subequal to distal width of peduncle. Sternite of 3rd maxillipeds with small spine on each side of midline. Antennular peduncle exceeding distal margin of corneae by half or more length of penultimate segment. Antennal peduncle ( Fig. 21c ) slightly exceeding distal margin of cornea; 3rd segment with strong ventromesial distal spine; 2nd segment with dorsolateral distal angle produced, terminating in strong spine, mesial margin with small spine on dorsodistal angle; acicles at most slightly exceeding distal margin of corneae, mesial margin armed with 5 to 7 spines; flagellum with setae 1 to 2 flagellar articles in length. Chelipeds markedly dissimilar, with moderately dense setae. Right cheliped (Fig. 2Ie,f) with fingers weakly curved ventromesially, dactyl with row of spines on mesial margin; palm with dorsal surface unarmed or at most with scattered small tubercles, dorsolateral and dorsomesial margins with row of spines, mesial face rounded and with few tubercles; carpus with numerous small tubercles or spines on dorsal surface. Left cheliped (Fig. 2Id) with chela unarmed, well calcified; carpus with dorsolateral face weakly calcified, 1 dorsodistal and 1 laterodistal spine. Ambulatory legs ( Fig. 21 g-i) usually exceeding tip of extended right cheliped; dactyls evenly curved, about 1.9 as long as propodi, each with ventromesial row of about 5 (2nd) or 2 (3rd) small corneous spines, and dorsal and dorsomesial rows of long setae; carpus with small dorsodistal spine; ischium and merus of 2nd pereopod unarmed. Anterior lobe of sternite of 3rd pereopods unarmed or with small marginal spine, setose. Fourth pereopod ( Fig. 21j ) with dactyl terminating in short, corneous claw; propodal rasp consisting of ovate scales. Uropods and telson markedly asymmetrical ( Fig. 21m ); telson lacking transverse suture; posterior lobes separated by shallow, U-shaped median cleft, terminal margins armed with often curved corneous spines. Male 1st gonopods ( Fig. 21k ) each with weakly concave distal lobe; 2nd gonopods (Fig. 211) each with distal segment nearly flat. Females with vestigial right 2nd pleopod.

Habitat and symbiotic associations. Unknown, probably gastropod shells.

Distribution. Indo Pacific: Maldives; Indonesia; and Australia. Depth: 800 to 2308 m.

Affinities. This species, and Sympagurus acinops Lemaitre, 1989 , from the eastern and western Atlantic Ocean, are the only parapagurids with subconical corneae. Other than in generic characters, the two species differ markedly in the length and armature of the antennal acicles, armature of chelipeds, and degree of development of male gonopods (see Lemaitre, 1989: 52, figs 24-27).

Remarks. De Saint Laurent (1972: 108) mentioned (without name) a form from the eastern Pacific (Gahipagos Islands; Gulf of Panama) which she considered close to, or conspecific with 0. minutus . She did not, however, discuss such taxon any further.

Figures

Fig. 21. Oncopagurus minutus (Henderson, 1896). a, shield and cephalic appendages; b, right ocular peduncle and cornea, lateral; c, right antennal peduncle, lateral; d, left cheliped; e, right cheliped; f, chela of same, mesial; g, left 2nd pereopod, lateral; h, left 3rd pereopod, lateral; i, dactyl of same, mesial; j, propodus and dactyl of left 4th pereopod, lateral; k, male left 1st gonopod, mesial; 1, male left 2nd gonopod, anterior; m, telson. Scale = 1 mm (a,d~i), and 0.5 mm (b,c,j~m). (Male [SL 2.5 mm], New South Wales, AM P40409).