Oncopagurus minutus ( Henderson, 1896 )

Lemaitre, Rafael, 2014, A worldwide taxonomic and distributional synthesis of the genus Oncopagurus Lemaitre, 1996 (Crustacea: Decapoda: Anomura: Parapaguridae), with descriptions of nine new species, Raffles Bulletin of Zoology 62, pp. 210-301 : 259-261

Oncopagurus minutus ( Henderson, 1896)

Figs. 27 , 51

Parapagurus minutus Henderson, 1896: 531 (type locality: off the north Maldive Atoll, RIMSS Investigator, sta 150); Alcock & Anderson, 1897, pl. 32, fig. 3, 3a; Alcock, 1901: 222; 1905: 101, pl.10, fig. 3; de Saint Laurent, 1972: 108; Miyake 1982: 196 (list).

Sympagurus minutus – Lemaitre, 1989: 37; 1994: 412.

Oncopagurus minutus – Lemaitre, 1996: 201 , fig. 21; 1997: 594; Zhadan,1999: 735, figs. 2a, b; Davie, 2002: 89; Poore, 2004: 282, fig. 81d; Asakura et al., 2006: 211; Asakura, 2006: 309; McLaughlin et al., 2010: 39.

(For complete synonymy see Lemaitre, 1996)

Type material. Syntype: F 2.3 mm, Indian Ocean , off north Maldive Atoll, RIMSS Investigator, sta 150, 1308.6 m ( BMNH 1896 :9.8.24) .

Additional material. Taiwan: TAIWAN 2006: sta CP 372, 24º23.619'N, 122º14.138'E, 1220–1280 m, 26 August 2006: 3 M 3.0– 4.1 mm, 1 ov F 2.8 mm ( NTOU) . Philippines: MUSORSTOM 2: sta CP 55, 13°54'N, 119°58'E, 865–866 m, 27 November 1980 (2 lots): 1 M 2.8 mm,1 ov F 3.6 mm ( MNHN Pg.), 1 F 2.8 mm, 1 ov F 3.0 mm ( MNHN Pg.) . Indonesia: CORINDON: sta CH 276, 01°55'S, 119°14'E, 395–450 m, 8 November 1980: 1 F 2.7 mm ( MNHN Pg.); [unknown sta]: 1 ov F 3.6 mm ( MNHN Pg.) . Solomon Islands: SALOMON 1: sta CP 1808, 9°45.5'S, 160°52.5'E, 611–636 m, 2 October 2000: 1 M 3.2 mm ( MNHN Pg.)) — SALOMON 2: sta CP 2176, 9°10.6'S, 159°01.14'E, 600 m, 21 October 2004: 2 ov F 2.1, 2.5 mm ( MNHN Pg.); sta CP 2231, 6°26.6'S, 156°24.4'E, 1083–1100 m, 29 October 2004: 1 M 2.6 mm ( MNHN Pg.) . Wallis and Futuna Islands : MUSORSTOM 7: sta CP 567, 11°47.0'S, 178°27.3'W, 1010–1020 m, 20 May 1992: 1 M 3.5 mm ( USNM 1211220 ) . Vanuatu: MUSORSTOM 8: sta CC 996, 18°52.41'S, 168°55.73'E, 764–786 m, 24 September 1994: 1 M 2.7 mm ( MNHN Pg.); sta CP 1008, 18°53.29'S, 168°52.65'E, 919–1000 m, 25 September 1994: 1 M 3.3 mm (MNHN-IU-2013-5499) — BOA 0: sta CP 2311, 14°44'S, 167°06'E, 932–986 m, 15 November 2004: 1 M 3.8 mm ( MNHN Pg.) . Tonga Islands : BORDAU 2: sta DW 1508, 21°02'S, 175°19'W, 555–581 m, 31 May 2000: 1 F 1.9 mm ( USNM 1211219 , ex MNHN Pg. 6719) . New Caledonia: BIOCAL: sta CP 55, 23°19.80'S, 167°30.70'E, 1160–1175 m, 1 September 1985: 1 ov F 2.8 mm (MNHN-IU-2013-5536); sta CP 57, 23°43.30'S, 166°58.10'E, 1490–1620 m, 1 September 1985: 1 M 2.5 mm ( USNM 1211225 ) — MUSORSTOM 5: sta DW 322, 21°19.00'S, 158°00.40'E, 975 m, 14 October 1986: 1 M 1.6 mm [parasitised] ( USNM 1211224 ); sta CP 323, 21°18.52'S, 157°57.62'E, 970 m, 14 October 1986: 1 M 2.7 mm ( USNM 1211223 ); sta CP 324, 21°15.01'S, 157°51.33'E, 970 m, 14 October 1986: 1 M 3.7 mm ( USNM 1211222 ) — BIOGEOCAL: sta CP 238, 21°27.64'S, 166°23.41'E, 1260–1300 m, 13 April 1987: 1 ov F 3.2 mm (MNHN-IU-2013-5513); sta DW 313, 20°58.95'S, 166°59.04'E, 1600–1640 m, 2 May 1987: 1 M 2.3 mm ( USNM 1211221 ) — BENTHAUS: sta CP 1911, 27°37.94'S, 144°15.23'E, 900–1300 m, 10 November 2002: 1 ov F 2.2 mm ( USNM 1211226 , ex MNHN Pg. 6718); sta DW 1956, 23°18.42'S, 149°26.96'E, 600–990 m, 18 November 2002: 1 M 1.7 mm ( MNHN Pg.); sta DW 2001, 22°26.59'S, 151°20.12'E, 200–550 m, 23 November 2002: 1 F 2.4 mm ( MNHN Pg.); sta DW 2005, 22°28.09'S, 151°18.30'E, 680–1800 m, 24 November 2002: 1 F 1.7 mm ( MNHN Pg.) — EBISCO: sta CP 2556, 21°06'S, 158°32'E, 741–791 m, 12 October 2005 (2 lots): 1 M 3.3 mm ( MNHN Pg.), 1 M 3.9 mm ( MNHN Pg.); sta CP 2557, 21°07'S, 158°30'E, 800–923 m, 12 October 2005: 2 M 2.4, 3.3 mm ( MNHN Pg.); sta CP 2615, 19°35'S, 158°48'E, 680–722 m, 19 October 2005: 1 ov F 2.1 mm ( MNHN Pg.); sta CP 2647, 21°32'S, 162°27'E, 747 m, 23 October 2005: 1 F 1.2 mm ( MNHN Pg.); sta CP 2648, 21°32'S, 162°30'E, 458–750 m, 23 October 2005: 4 M 1.7–2.7 mm ( MNHN Pg.); sta CP 2650, 21°27'S, 162°33'E, 825–894 m, 23 October 2005: 1 M 2.5 mm ( MNHN Pg.) . Marquesas : MUSORSTOM 9: sta DW 1286, 7°53.1'S, 140°39.2'W, 760 m, 7 September 1997: 1 M 2.4 mm (MNHN-IU-2013-5511, ex MNHN Pg. 6420) .

For additional material examined see Lemaitre (1996).

Diagnosis. Shield ( Fig. 27A ) about as long as broad; rostrum broadly rounded, with short, low mid-dorsal ridge; lateral projections subtriangular, terminating in small spine. Ocular peduncles more than half length of shield, diminishing in width distally, with long setae dorsally; ocular acicles subtriangular, terminating in strong spine; corneas subconical, distally rounded, maximum width of each subequal to distal width of peduncle at base of cornea ( Fig. 27A, B ). Antennular peduncle ( Fig. 27A ) exceeding distal margin of cornea by half or more length of penultimate segment. Antennal peduncle ( Fig. 27A ) slightly exceeding distal margin of cornea; fourth segment with small spine on dorsolateral distal angle; second segment with dorsolateral distal angle terminating in strong spine, mesial margin with small spine on dorsodistal angle; acicle at most slightly exceeding distal margin of cornea, mesial margin armed with 5–7 spines; flagellum with setae 1 to 2 flagellar articles in length. Third maxilliped with crista dentata of about 10–13 teeth gradually dimishising in strength distally. Chelipeds markedly dissimilar, with moderately dense setae. Right cheliped ( Fig. 27C, D ) with moderately dense setae, chela operculate; dactyl set at strongly oblique angle to longitudinal axis of palm; palm with dorsal surface unarmed or at most with scattered small tubercles, dorsolateral and dorsomesial margins well defined by row of small spines or tubercles, mesial face rounded and with few tubercles; carpus with numerous and generally well-spaced small tubercles or spines on dorsal surface. Left cheliped with carpus weakly calcified dorsolateral face; palm unarmed except for few setae; carpus with dorsodistal spine. Ambulatory legs with dactyls ( Fig. 27E ) having ventromesial row of about 2–5 small corneous spinules; carpus with small dorsodistal spine. Anterior lobe of sternite XII (between second ambulatory legs) unarmed or with small subterminal spine, setose. Fourth pereopod propodal rasp ( Fig. 27F ) with 1 row of ovate scales at least distally. Uropods and telson markedly asymmetrical; telson ( Fig. 27G ) lacking transverse suture, posterior lobes separated by shallow, U-shaped median cleft, terminal margins armed with often curved corneous spines. Male with paired first and second gonopods ( Fig. 27H, I ); first gonopod with weakly concave distal lobe; second gonopod with distal segment nearly flat, setose distally. Females with vestigial right second pleopod.

Colouration. Unknown

Habitat. Gastropod shells.

Distribution. Indo-Pacific: from the Maldives in the Indian Ocean; and from Indonesia to the Marquesas in the Western to Central Pacific. Depth: 200–2308 m.

Remarks. (See also Oncopagurus conicus , O. elongatus , new species, and O. petilus , new species). As previously mentioned, O. minutus and three other congeners, O. conicus , O. elongatus , new species, and O. petilus , new species, are set apart from other Oncopagurus species in having reduced, subconical corneas. Oncopagurus minutus differs from those species as follows: from O. conicus in having an operculate right chela (not operculate in O. conicus ), and the uropods and telson are asymmetrical in O. minutus (symmetrical in O. conicu s); from O. elongatus , new species in the shape and armature of the mesial face of the right chela, which is rounded in O. minutus , whereas in O. elongatus , new species the mesial face can be rounded (males) or concave and expanded distomesially with a well delimited ventromesial margin, and the dactyl of the fourth pereopod, which in O. minutus is similarly shaped in both sexes ( Fig. 27F ), whereas in O. elongatus , new species, the dactyl is distinctly longer and slenderer in females than in males; from O. petilus , new species, in the length of the antennal acicles relative to the ocular peduncles, not exceeding the corneas in O. minutus (acicles distinctly exceeding the corneas in O. petilus , new species, and the ventromesial face of the right chela rounded (with ventromesial row of spines in O. petilus , new species.

Oncopagurus minutus is broadly distributed. It has been found from the Maldives, in the central Indian Ocean, throughout the tropical western Pacific, and the Marquesas in the Central Pacific. Bathymetrically it reaches to 2308 m in depth ( Fig. 51 ), the deepest among species of Oncopagurus .

Figures

Fig. 27. Oncopagurus minutus (Henderson, 1896): male 2.5 mm, New South Wales, Australia (AM P40409). A, shield and cephalic appendages, dorsal; B, right ocular peduncle, lateral; C, right cheliped, dorsal; D, chela of same mesial; E, dactyl of first ambulatory leg, mesial; F, propodus and dactyl of left fourth pereopod, lateral; G, telson, dorsal; H, left first gonopod, mesial; I, left second gonopod, anterior. Scale bars = 1 mm (A, C–E), 0.5 mm (B, F–I)). [Adapted from Lemaitre (1996)].

Fig. 51. Bathymetric distribution of Oncopagurus species from the world, with maximum and minimum depths (meters) indicated for each.