Oncopagurus gracilis ( Henderson, 1888 )

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 : 252-253

Oncopagurus gracilis ( Henderson, 1888)

Figs. 25A–J , 51

Eupagurus bicristatus A. Milne-Edwards, 1880: 43 (in part, see Remarks).

Parapagurus gracilis Henderson, 1888: 92 , pl. 10, fig. 3 (type locality: off Pernambuco, Brazil, HMS Challenger, sta 122, 09°05'S, 34°50'W); Rieger, 1998: 413.

Sympagurus arcuatus A. Milne-Edwards & Bouvier, 1893: 67 , pl. 5, figs 21–28 (type locality: St. Lucia, Caribbean Sea , USCGS Blake, sta 218, 13°49.12'N, 61°04.40'S).

Pylopagurus exquisitus Boone, 1927: 71 , fig. 14 (type locality: Pawnee I, N of Glover Reef , off the coast of British Honduras [= Belize])

Parapagurus bicristatus gracilis – de Saint Laurent, 1972: 112; Coelho & Ramos-Porto, 1987: 38.

Sympagurus gracilis – Lemaitre, 1989: 64, figs 32–35, 40C; Melo, 1999: 156, figs 95, 96.

Parapagurus arcuatus – Williams et al., 1989: 32.

Oncopagurus gracilis – Lemaitre, 1996: 194; McLaughlin et al., 2005: 246; Coelho et al., 2007: 10 (Table 1); Felder et al., 2009: 1071; McLaughlin et al., 2010: 39; Campos et al., 2005: 139, figs. 99, 100; Martínez Campos et al., 2012: 240.

(For complete synonymy see Lemaitre, 1989)

Type material. Lectotype designated by Lemaitre (1989): M 2.8 mm, off Pernambuco, Brazil, HMS Challenger , sta 122, 09°05'S, 34°50'W, 630 m, 10 September 1883 ( BMNH 1888 : 33).

Holotype of Sympagurus arcuatus A. Milne-Edwards & Bouvier, 1893 : ov F 2.6 mm, off St. Lucia, Caribbean Sea , USCGS Blake, sta 218, 13°49.12'N, 61°04.40'S, 295 m, 15 February 1879 ( MCZ 6330 ).

Additional material. est Africa : Atlantide Expedition, sta 135, 07°55'S, 12°33'E, off Angola, 235–460 m, 17 March 1946: 1 M 4.5 mm ( ZMK) .

For additional material see Lemaitre (1989, as Sympagurus gracilis ).

Diagnosis. Shield ( Fig. 25A ) about as broad as long; rostrum broadly rounded, weakly produced to obsolete, with short mid-dorsal ridge; lateral projections subtriangular, slightly in advance of rostrum, often terminating in small spine. Ocular peduncles usually more than half length of shield, with dorsal row of setae; corneas weakly dilated. Ocular acicles subtriangular, terminating in strong spine. Antennular peduncle ( Fig. 25A ) exceeding distal margin of cornea by nearly entire length of ultimate segment. Antennal peduncle ( Fig. 25A ) not exceeding distal margin of cornea; fourth segment with small spine on dorsolateral distal angle; second segment with dorsolateral distal angle terminating in strong, simple or multifid spine, mesial margin with spine on dorsodistal angle; first segment with small spine on lateral face; acicles weakly curved (in dorsal view), usually not exceeding distal margin of corneas, terminating in strong spine, mesial margin armed with row of 7–11 spines each set at about 45° angle to longitudinal axis of acicle; flagellum exceeding extended right cheliped, with series of 2 or or 3 long setae 4–8 articles in length every 10–20 articles. Third maxilliped with crista dentata of about 10 teeth, proximal 2 or 3 teeth usually larger than distal. Right cheliped ( Fig. 25B–E ) with moderately dense, simple and plumose setae, chela operculate, proportions and armature of chela, and carpus strongly influenced by size and sexual dimorphism; dactyl set at strongly oblique angle to longitudinal axis of palm; palm varying from broader than long to longer than broad, dorsal face with irregular rows of scattered small tubercles or spines medially, dorsolateral and dorsomesial margins well delimited by row of blunt to sharp spines, mesial face strongly sloping, ventromesial face rounded, ventral face smooth; carpus 1.3–1.8 times as long as broad, dorsolateral margin usually well delimited by row of spines at least distally, dorsal face with numerous, well-spaced small spines or tubercles. Left cheliped usually weakly well calcified on dorsolateral face of carpus; palm unarmed except for dorsomesial row of small spines and long setae on dorsomesial margin; carpus with strong dorsodistal spine and long setae dorsally. Ambulatory legs with dactyls ( Fig. 25F ) each having ventromesial row of about 3–9 corneous spinules; carpus with small dorsodistal spine. Anterior lobe of sternite XII (between second ambulatory legs) rounded, setose, with 1 or 2 subterminal spines. Fourth pereopod propodal rasp ( Fig. 25G ) with 1 row of rounded scales at least distally. Fifth pereopod propodal rasp extending to or beyond mid-length of segment. Uropods and telson markedly asymmetrical; telson ( Fig. 25H ) lacking or with obsolete transverse suture, posterior lobes separated by shallow V-shaped cleft, terminal margin of lobes armed with often strongly curved corneous spines. Male with paired first and second gonopods ( Fig. 25I, J ), small individuals (sl <1.6 mm) often lacking first gonopods; first gonopods with ovate distal lobe, marginally setose; second gonopods with distal segment spatulate and with setae distally. Female with vestigial second right pleopod.

Variations. See Lemaitre (1989, as Sympagurus gracilis )

Colouration. Unknown.

Habitat. Gastropod shells frequently with one or more anthozoan polyps (actinians or zoanthids) attached.

Distribution. Western Atlantic, from the Straits of Florida and Gulf of Mexico to off Pernambuco, Brazil. Eastern Atlantic, form Gulf of Guinea and off Angola. Depth 146– 634 m.

Remarks. (See also Oncopagurus africanus and O. bicristatus ). As discussed by Lemaitre (1989), one of the two type specimens used to describe Eupagurus bicristatus A. Milne Edwards, 1880 (= Oncopagurus bicristatus ) was also used by A. Milne-Edwards & Bouvier (1893) to describe Sympagurus arcuatus . That taxon and Pylopagurus exquisitus Boone, 1927 , were shown by Lemaitre (1989) to be junior synonyms of Parapagurus gracilis Henderson, 1888 (= O. gracilis ).

Oncopagurus gracilis and O. bicristatus are the only two species of Oncopagurus that occur in the western Atlantic, where they occur sympatrically. Both also range to the eastern Atlantic. In the eastern Atlantic, O. gracilis has been found in the Gulf of Guinea and off Angola. Oncopagurus gracilis differs from O. bicristatus in the shape of the right palm, armature of antennal acicles, and in males, degree of development of the first and second gonopods. In O. gracilis , the ventromesial face of the right palm is rounded, whereas in O. bicristatus there is a distinct, spinose ventromesial margin. In O. gracilis , the spines on the mesial margin of the antennal acicle are set at about a 45° angle with the longitudinal axis of the acile, whereas in O. bicristatus the spines are set at nearly 90° angle. The first and second gonopods in O. gracilis are fairly well developed for a species of Oncopagurus , whereas in O. bicristatus the first gonopods are reduced to short buds and the second gonopods are either poorly developed or asymmetrical.

Figures

Fig. 25. A–J, Oncopagurus gracilis (Henderson, 1888): A, male 5.5 mm, Straits of Florida, Bellows sta 78-8 (USNM 1100625); B, female 2.7 mm Caribbean Sea, Pillsbury, sta 610 (UMML 32: 4600); C, male 2.2 mm, SW Atlantic, Oregon sta 4226 (UMML 32: 4538); G–H, male 4.6 mm, Caribbean Sea, Oregon sta 4423 (UMML 32:4591); I, J, male 5.5 mm, SW Atlantic, Oregon sta 4226 (UMML 32: 4538): A, shield and cephalic appendages, dorsal; B-D, carpus and chela of right cheliped; E, right chela, lateral; F, dactyl of left first ambulatory leg, mesial; G, propodus and dactyl of left fourth pereopod, lateral; H, telson, dorsal; I, left first gonopod, mesial; J, left second gonopod, anterior. K–R, Oncopagurus haigae (de Saint Laurent, 1972): K–M, O–Q, male 4.2 mm, off Chile, USNS Eltanin, sta 71 (USNM 216289); N, male 3.9 mm, R, female 3.0 mm, off southern California, Albatross, sta 2935 (USNM 216289): K, shield and cephalic appendages, dorsal; L, N, carpus and chela of right cheliped, dorsal; M, chela, mesial; O, dactyl of right first ambulatory leg, lateral; P, propodus and dactyl of left fourth pereopod, lateral; Q, R, telson, dorsal; S, second pair of gonopods, lateral (right on right, left on left). Scale bars = 3 mm (A, F, K); 2 mm (B, C); 4 mm (D, E); 1 mm (H, G, P–R); 0.5 mm (I, J); 5 mm (L, N, O); 1 mm (S). [Adapted from Lemaitre (1989), and Lemaitre & McLaughlin (1992)].

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