Oncopagurus crusoei, Lemaitre, 2014

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 : 231-237

Oncopagurus crusoei , new species

Figs 11–14 , 51

Type material. Holotype, eastern Pacific , SEPBOP, R/ V Anton Bruun, cruise 12: sta 65–MV–IV–47, off Cumberland Bay , Más a Tierra Island, Juan Fernández Islands, [33°38'29"S 78°50'28"W], 130–160 m, 12 December 1965: M 1.9 mm ( USNM 1207981 ).

Paratypes: eastern Pacific , same stn as holotype: 1 M 1.6 mm, 2 F 1.3, 1.8 mm, 2 ov F 1.5, 1.8 mm ( USNM 1207982 ) .

Description. Gills biserial. Shield ( Fig. 11A ) about as long as broad or slightly longer than broad; dorsal surface weakly calcified medially (weak calcification often reaching to anterior margin), with scattered short setae; rostrum broadly rounded, weakly produced, with short mid-dorsal ridge; anterior margins weakly concave; lateral projections subtriangular, terminating in small blunt or sharp spine; anterolateral margins sloping; posterior margin broadly rounded; ventrolateral margins of shield usually with slender spine on one or both sides. Anterodistal margin of branchiostegite rounded, unarmed, setose.

Ocular peduncles ( Fig. 11A ) stout, more than half length of shield, with longitudinal row of few short setae dorsally; lateral and ventral faces usually weakly calcified. Cornea weakly dilated. Ocular acicles subtriangular, each terminating in strong spine; separated basally by about basal width of 1 acicle.

Antennular peduncle ( Fig. 11A ) exceeding distal margin of cornea by about 0.75 length or ultimate segment. Ultimate segment about twice as long as penultimate segment, naked or with scattered setae dorsally. Basal segment with strong ventromesial spine; lateral face with distal subrectangular lobe, and strong spine proximally. Ventral flagellum with 5 articles.

Antennal peduncle ( Fig. 11A, B ) not exceeding distal margin of cornea, reaching to about distal 0.7 of cornea. Fifth segment unarmed except for scattered setae and laterodistal tuft of setae. Fourth segment armed with strong dorsodistal spine. Third segment with strong ventromesial distal spine. Second segment with dorsolateral distal angle produced, terminating in strong simple spine; mesial margin with spine on dorsodistal angle. First segment with lateral face unarmed or with small blunt spine; ventromesial angle produced, with 2 or 3 small spines laterally. Acicle relatively short, reaching to about proximal margin of cornea, nearly straight (in dorsal view), terminating in strong spine; mesial margin armed with 6–8 spines, sparsely setose. Flagellum slightly exceeding extended right cheliped, articles with setae less than 1–2 flagellar articles in length.

Maxillule with external lobe of endopod slender, moderately developed, not recurved, internal lobe with long, terminal seta. Third maxilliped crista dentata with about 10 teeth, proximal 2 or 3 teeth distinctly larger than distal.

Chelipeds markedly dissimilar. Right cheliped ( Fig. 13A–E ) massive, chela operculate, usually more elongate in males than in females; carpus and chela with sparse to moderately dense setae on dorsal surfaces, setae more dense on dorsal surfaces of fingers and mesial face of carpus. Fingers curved ventromesially, each terminating in small, usually blunt corneous claw; cutting edges with 2 or 3 large calcareous teeth and several irregularly sized smaller calcareous teeth, with short row of closely set minute corneous teeth distally on dactyl. Dactyl varying 1.0–1.3 times as long as mesial margin of palm, set at moderately (in large males ~ sl 1.9 mm) to strongly oblique angle to longitudinal axis of palm; mesial margin broadly curved, delimited by row of spines diminishing in size distally; dorsal face with moderately dense small spines or tubercles decreasing in density mesially and distally; ventromesial face concave and elevated longitudinally on midline. Fixed finger broad at base, dorsal face covered with moderately dense small spines or tubercles, lateral margin delimited by row of spines; ventrolateral face concave and elevated longitudinally on midline. Palm ranging from slightly broader than long to 1.3 times as long as broad; dorsal surface covered with moderately dense small spines or tubercles; dorsolateral margin nearly straight, delimited by irregular row of small blunt or sharp spines; mesial margin rounded, with well-spaced spines or tubercles; ventral surface covered with well–spaced small spines or tubercles, at most with scattered short setae. Carpus longer than broad, dorsal surface and sometimes also ventral surface, covered with moderately dense small spines or tubercles; dorsolateral face rounded; dorsodistal margin with row of small spines; ventral face nearly flat. Merus with scattered setae dorsally, and moderately dense setae ventrodistally; with scattered small tubercles on dorsal surface; ventromesial margin with row of blunt to sharp spines; ventrolateral margin with row of small tubercles. Ischium with ventromesial row of small, blunt spines. Coxa row of small spines on ventrodistal margin, and ventromesial row of setae.

Left cheliped ( Fig. 13F, G ) usually weakly calcified on nearly entire dorsolateral face of carpus. Fingers each terminating in small corneous claw; dorsal and ventral surfaces unarmed except for scattered tufts of setae; cutting edge of dactyl with row of minute, fused corneous teeth; cutting edge of fixed finger with row of well-spaced small calcareous teeth. Dactyl about as long as length of mesial margin of palm, with scattered tufts of setae; with 1 or 2 small proximal spines or tubercles on dorsal face. Fixed finger with scattered tufts of setae. Palm with dorsomesial row of small spines or tubercles, and scattered setae; ventral face smooth except for scattered setae. Carpus with dorsal irregular row of small spines in addition to dorsodistal and dorsolateral spine on distal margin; dorsal surface with long setae; ventral face smooth except for scattered setae. Merus with long setae on dorsal margin; with ventrolateral row of small spines; ventral face smooth. Ischium and coxa unarmed, but with ventromesial row of setae.

Ambulatory legs ( Fig. 14A–C ) similar right from left except for longer segments and stronger spination on right, extending to about tip of dactyls of right cheliped or slightly exceeding them. Dactyls broadly curved, about 1.5 times as long as propodi, and terminating in sharp corneous claws; each with dorsal and dorsomesial distal rows of long setae, and 4–9 small spinules on ventromesial margin. Propodi with setae on dorsal margin; ventral margin with few setae. Carpi each with setae on dorsal margin, and small dorsodistal spine. Meri each with setae on dorsal margin, otherwise unarmed. Ischia with setae on dorsal and ventroproximal margin. Coxae with ventromesial row of setae. Anterior lobe of sternite XII (between second ambulatory legs, Fig. 11C ), setose, with subdistal spine.

Fourth pereopod ( Fig. 14D ) semichelate. Dactyl terminating in sharp corneous claw; with ventrolateral row of small corneous spinules. Propodus longer than broad, rasp with 1 row of rounded scales at least distally. Carpus with long setae on dorsal margin. Merus with rows of long setae on dorsal and ventral margins. Coxa with anteroventral row of setae. Anterior lobe of sternite XIII (between fourth pereopods) with row of setae.

Fifth pereopod ( Fig. 14E ) semichelate. Propodal rasp reaching or exceeding mid-length of segment. Coxa with row of long setae on anteroventral and ventrodistal margins. Anterior lobe of sternite XIV (between fifth pereopods) with row of setae.

Uropods markedly asymmetrical; left exopod ( Fig. 11D ) about 2.3 times as long as broad, rasp consisting of 2–4 rows of small scales. Telson ( Fig. 11E ) moderately asymmetrical, lacking transverse suture; dorsal surface with scattered setae; lateral margins with few setae medially; posterior lobes separated by shallow unarmed, U-shaped cleft; terminal margin of left lobe armed with about 6–8, often weakly curved corneous spines, terminal margin of right lobe armed with 4 or 5 small spines.

Male with paired first and second gonopods ( Fig. 11F, G ); first gonopod with distal portion subovate, with setae distally; second gonopod with distal segment flat and with long setae distally, proximal segment with long setae distomesially. Females with vestigial second right pleopod.

Variations. Even in the few known specimens of this new species, variations of the right cheliped due to sex and size are noticeable. As is typical in most congeners and many other parapagurids, the right cheliped is long and slender in large males ( Fig. 13A ), and broad and short in females ( Fig. 13E ).

Colouration. Unknown.

Habitat. Gastropod shells.

Distribution. So far known only from the eastern Pacific, in the Juan Fernández Islands, Chile. Depth: 130– 160 m.

Remarks. Oncopagurus crusoei , new species, is only the second species of Oncopagurus documented from the entire eastern Pacific, the other being O. haigae . This new species distinctly differs from O. haigae in various characters. In this new species, the ocular peduncles are stouter than in O. haigae ; the antennal acicles reach to about the proximal margin of the corneas, whereas in O. haigae the acicles exceed the cornea by 0.3–0.5 the length of the acicle. In this new species, the armature of the dorsal and ventral surfaces of the carpus and chela of the right cheliped is generally stronger and with more numerous spines or tubercles, whereas in O. haigae the dorsal surface armature is mostly of scattered small spines (sometimes arranged medially in irregular rows), and the ventral surfaces are unarmed or at most with occasional small tubercles. In this new species, the dorsal margin of the carpus of the left cheliped is armed with an irregular row of mostly sharp spines, whereas in O. haigae the carpus is unarmed dorsally except for a dorsodistal spine. The telson ( Fig. 11E ) in this new species is moderately asymmetrical in both sexes, and at least based on the available material, there is no strong dimorphism in telson shape and armature. In contrast, the telson in females of O. haigae have strongly asymmetrical terminal lobes armed with more spines and rows than in males ( Fig. 25R ). Males of O. crusoei , new species, have paired first and second gonopods ( Fig. 11F, G ), whereas males of O. haigae lack first gonopods and the second gonopods are asymmetrical.

Etymology. The species is named in honor of Robinson Crusoe, the fictional castaway character in the famous novel by Daniel Defoe. The novelist was most likely inspired by the experience of Alexander Selkirk, a Scottish sailor who was marooned in the early 18 th century in the island of Más a Tierra, one of the Juan Fernández Islands later renamed Robinson Crusoe Island.

Figures

Fig. 11. Oncopagurus crusoei, new species, holotype, male 1.9 mm, Juan Fernández Islands (USNM 1207981). A, shield and cephalic appendages, dorsal; B, right ocular peduncle, lateral; C, anterior and posterior lobes of thoracic sternite XII (between second ambulatory legs), ventral; D, exopod of left uropod, dorsal; E, telson, dorsal; F, left first gonopod, mesial; G, left second gonopod, anterior. Scale bars = 0.5 mm.

Fig. 12. Oncopagurus crusoei, new species, paratype, ov female 1.8 mm, Juan Fernández Islands (USNM 1207982). Left mouthparts, internal: A, distal half of mandible; B, maxillule; C, maxilla; D, first maxilliped; E, second maxilliped; F, third maxilliped. Scale bar = 0.25 mm.

Fig. 13. Oncopagurus crusoei, new species, Juan Fernández Islands:A–D, F, G, holotype, male 1.9 mm (USNM 1207981); E, paratype, ov female 1.5 mm (USNM 1207982). A, E, right cheliped, dorsal; B–D, chela of same, lateral (B), mesial (C), ventral (D); F, left cheliped, dorsal; G, carpus of same, dorsolateral. Scale bars = 1 mm (A–D), 0.5 mm (E–G).

Fig. 14. Oncopagurus crusoei, new species, holotype, male 1.9 mm, Juan Fernández Islands (USNM 1207981). A, right first ambulatory leg, lateral; B, dactyl of same, mesial; C, right second ambulatory leg, lateral (distal portion of dactyl missing); D, propodus and dactyl of left fourth pereopod, lateral; E, propodus and dactyl of left fifth pereopod, lateral. Scale bars = 0.5 mm (A–C), 1 mm (D, E).

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

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)].