Oncopagurus rossanae, 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 : 277-283

Oncopagurus rossanae , new species

Figs. 38–41 , 51 , 53E, F

Oncopagurus n. sp. 2 – McLaughlin et al., 2010: 39.

Type material. Holotype, French Polynesia, Austral Islands , BENTHAUS, sta DW 1973, Arago Bank, 23°23.49'S, 150°43.87'W, 200–350 m, 20 November 2002: M 2.9 mm (MNHN-IU-2013-6869).

Paratypes, Marquesas Islands: MUSORSTOM 9: sta DW 1145, 9°19.0'S, 140°06.3'W, 150–180 m, 22 August 1997: 1 ov F 1.2 mm ( MNHN Pg. 6424); sta DW 1146, 9°18.8'S, 140°06.2'W, 200 m, 22 August 1997: 2 M 2.4, 2.7 mm, 6 ov F 1.4–2.1 mm ( USNM 1207996 , ex MNHN Pg. 6422); sta DW 1148, 9°18.9'S, 140°06.3'W, 300 m, 22 August 1997: 3 M 2.0– 2.6 mm, 1 F 1.6 mm, 4 ov F 1.8–2.0 mm ( MNHN Pg. 6416); sta DW 1172, 8°44.8'S, 140°15.3'W, 300–302 m, 25 August 1997: 1 F 1.3 mm, 1 ov F 1.7 mm ( MNHN Pg. 6423); sta DR 1197, 8°57.4'S, 140°01.9'W, 277–372 m, 27 August 1997: 3 M 1.6–2.4 mm ( MNHN Pg. 6425); sta DR 1198, 9°50.0'S, 139°09.4'W, 290–320 m, 28 August 1997: 1 M 1.5 mm ( MNHN Pg. 6429); sta DR 1199, 9°49.2'S, 139°09.6'W, 210–258 m, 28 August 1997: 3 M 1.5–1.9 mm, 1 ov F 1.6 mm ( MNHN Pg. 6430); sta DW 1201, 9°50.6'S, 139°09.2'W, 275–300 m, 28 August 1997 (2 lots): 5 M 1.2–2.4 mm, 3 ov F 1.9–2.0 mm ( USNM 1207997 , ex MNHN Pg. 6419), 1 M 2.3 mm ( MNH Pg. 6426); sta DR 1231, 9°42.5'S, 139°05.1'W, 270–285 m, 31 August 1997: 2 M 1.6, 1.9 mm ( MNHN Pg. 6427); sta DR 1253, 9°47.9'S, 139°38.1'W, 360–405 m, 2 September 1997: 1 M 1.3 mm ( MNHN Pg. 6431); sta CP 1268, 7°55.8'S, 140°42.6'W, 285–320 m, 4 September 1997: 1 ov F 2.5 mm ( MNHN Pg. 6421); sta DW 1287, 7°54.5'S, 140°40.2'W, 163–245 m, 7 September 1997 (2 lots): 13 M 1.5–3.0 mm, 4 ov F 1.8–2.4 mm ( MNHN Pg. 6418), 1 F 1.6 mm ( MNHN Pg. 6417); sta DW 1288, 8°53.9'S, 139°38.0'W, 200–220 m, 8 September 1997: 6 M 1.4–2.5 mm, 3 ov F 1.3–1.8 mm ( MNHN Pg. 6428). French Polynesia , Austral Islands: BENTHAUS: sta DW 1869, Mac Donald Bank , 28°58.4'S, 140°15.4'W, 240–440 m, 4 November 2002: 2 M 1.4, 1.5 mm, 1 F 1.3 mm, 1 ov F 1.4 mm ( MNHN Pg. 6688); sta DW 1880, Marotiri, 27°54.8'S, 143°29.45'W, 90–94 m, 6 November 2002: 1 F 1.2 mm 1 ov F 1.4 mm ( MNHN Pg. 6876); sta DW 1881, Marotiri, 27°54.6'S, 143°28.5'W, 112–121 m, 6 November 2002: 5 M 1.2–2.1 mm, 2 F 1.1, 2.3 mm, 3 ov F 1.1–1.6 mm ( MNHN Pg. 6689); sta DW 1885, Marotiri, 27°51.87'S, 143°32.59'W, 700–800 m, 6 November 2002: 1 F 2.2 mm ( MNHN Pg. 7027); sta DW 1889, Rapa, 27°36.87'S, 144°15.75'W, 600–620 m, 7 November 2002: 10 M 1.7–2.6 mm, 3 F 1.2–2.3 mm ( MNHN Pg. 6690); sta DW 1901, Rapa NE Bank, 17°24.8'S, 144°01.67'W, 115–120 m, 9 November 2002: 36 M 2.0– 2.6 m, 9 F 1.6–2.8 mm, 15 ov F 2.2–2.4 mm ( MNHN Pg. 6691); sta DW 1905, Rapa NE Bank, 27°25.36'S, 144°02.62'W, 120–140 m, 9 November 2002: 3 M 2.0– 2.7 mm, 2 F 1.8, 2.2 mm, 1 ov F 2.3 mm ( USNM 1207998 , ex MNHN Pg. 6692); sta CP 1906, Rapa NE Bank, 27°24.78'S, 144°01.75'W, 110–127 m, 9 November 2002: 3 M 1.9–2.2 mm, 2 ov F 2.1, 2.4 mm ( USNM 1207999 , ex MNHN Pg. 6693); sta DW 1913, Neilson Reef, 27°01.55'S, 146°00.3'W, 120 m, 11 November 2002: 1 M 1.5 mm, 3 F 1.2–1.5 mm, 4 ov F 1.3–2.6 mm ( USNM 1208000 , ex MNHN Pg. 6694); sta CP 1918, Neilson Reef, 27°03.45'S, 146°03.96'W, 130–140 m, 12 November 2002: 1 ov F 1.1 mm (MNHN-IU-2013-6870); sta CP 1920, Neilson Reef, 27°03.58'S, 146°03.84'W, 120–203 m, 12 November 2002: 4 M 2.3–2.4 mm, 1 F 1.1 mm ( USNM 1208001 , ex MNHN Pg. 6695); sta DW 1929, Thiers Bank, 24°38.61'S, 146°01.61'W, 350–370 m, 13 November 2002: 1 M 1.6 mm ( MNHN Pg. 7028); sta DW 1941, Raevavae, 23°49.05'S, 147°41.6'W, 290–620 m, 15 November 2002: 1 M 2.7 mm ( MNHN Pg. 6696); sta DW 1951, Lotus Bank Raevavae, 23°49.08'S, 147°53.38'W, 206–450 m, 17 November 2002 (2 lots): 1 M 1.3 mm, 1 F 1.6 mm ( MNHN Pg. 7029), 1 M 2.8 mm ( MNHN Pg. 6697); sta DW 1961, Tubuai, 23°20.89'S, 149°33.51'W, 470–800 m, 19 November 2002: 3 M 1.3–1.8 mm ( MNHN Pg. 7030); sta DW 1972, Arago Bank, 23°21.96'S, 150°42.87'W, 500–1000 m, 20.22.2001: 1 M 1.7 mm ( MNHN Pg. 7031); sta DW 1973, Arago Bank, 23°23.49'S, 150°43.87'W, 200–350 m, 20 November 2002: 8 M 1.7–3.2 mm, 3 F 1.5–1.7 mm, 4 ov F 1.1.6– 2.3 mm ( MNHN Pg. 7032); sta DW 1974, Arago Bank, 23°23.93'S, 150°43.93'W, 450–618 m, 20 November 2002: 1 ov F 1.5 mm ( MNHN Pg. 7033); sta DW 1998, Rurutu, 22°24.81'S, 151°22.17'W, 250–302 m, 23 November 2002: 1 M 1.9 mm ( MNHN Pg. 6698); sta DW 2015, Rimatara, 22°38.16'S, 152°49.55'W, 250–280 m, 25 November 2002: 1 M 2.0 mm ( USNM 1208002 , ex MNHN Pg. 6699) .

Description. Gills biserial. Shield ( Fig. 38A, B ) about as long as broad; dorsal surface moderately to 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. 38A, B ) more than half length of shield; with longitudinal row of moderately long 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. 38A, B ) exceeding distal margin of cornea by 0.7 to nearly full length or ultimate segment. Ultimate segment not quite twice as long as penultimate segment, with scattered setae dorsally. Basal segment with strong ventromesial spine; lateral face with distal subrectangular lobe armed with small spine, and strong spine proximally. Ventral flagellum with 5 or 6 articles.

Antennal peduncle ( Fig. 38A, B ) not reaching distal margin of cornea (usually reaching to about midportion 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, usually simple spine; mesial margin with spine on dorsodistal angle. First segment with lateral face armed with small spine; ventromesial angle produced, with 2 or 3 small blunt 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 4–8 spines, sparsely setose. Flagellum long, slightly exceeding extended right cheliped, articles with long setae 1 or 2 flagellar articles in length every 3 or 4 articles, and scattered short setae <1 article in length.

Mandible ( Fig. 39A ) with 3-segmented palp; cutting edge calcified, with small tooth medially; molar process with small corneous tooth medially. Maxillule ( Fig. 39B ) with external lobe of endopod slender, moderately developed, not recurved, internal lobe with long, terminal seta. Maxilla ( Fig. 39C ) with endopod exceeding distal margin of scaphognathite. First maxilliped ( Fig. 39D ) with endopod distinctly exceeding exopod in distal extension. Second maxilliped ( Fig. 39E ) without distinguishing characters. Third maxilliped ( Fig. 39F ) with merus to dactyl each distinctly longer than broad, ischium about twice as long as broad; crista dentata with about 9 sharp teeth diminishing in strength distally; basis with 1 or 2 small mesial spines; coxa lacking spine. Sternite of third maxillipeds unarmed or with small spine on each side of midline

Chelipeds markedly dissimilar; dorsal surfaces of meri, carpi and propodi with some iridescence. Right cheliped ( Fig. 40A–C ) massive, chela operculate; chela varying considerably in shape and strength or armature with sex or size (see Variations); carpus and chela with sparse to moderately dense, mostly plumose setae on dorsal surfaces, setae more dense on dorsal surfaces of fingers and distally on dorsal and ventral faces of carpus. Fingers curved ventromesially, each terminating in small, usually blunt corneous claw; cutting edges with 3 or 4 large and several small calcareous teeth. Dactyl in males about as long as mesial margin of palm or in females longer than mesial margin of palm, set at strongly oblique angle to longitudinal axis of palm; mesial margin broadly curved, well delimited by row of strong spines diminishing in size distally; dorsal face with scattered small spines or tubercles; ventral face with short, usually tuberculate median longitudinal ridge proximally; ventromesial face concave. Fixed finger broad at base, dorsal face with scattered small spines or tubercles, lateral margin well delimited by row of spines; ventrolateral face concave. Palm about 1.2 times as broad as long in males ( Fig. 40A ), about 1.5 times as broad as long in females ( Fig. 40C ); dorsal surface with numerous well-spaced small spines or turbercles; dorsolateral margin broadly rounded or sometimes arching ( Fig. 40A, C ), sharply delimited by row of distally upturned spines which can be strong, dorsomesial margin delimited by row of small spines or tubercles; dorsomesial face rounded; ventral surface ( Fig. 40B ) naked or with scattered short setae, usually with a submedian longitudinal tuberculate ridge branching towards fixed finger and ventromesial distal angle of palm (ridges often forming a Y-shape), with small, moderately concave area medially; ventrolateral surface concave. Carpus longer than broad in males and about as long as broad or broader than long in females, much broader distally than proximally (distal width 2.0–2.5 times as large as proximal width); dorsolateral margin usually well delimited by row of small to strong spines; dorsodistal margin with row of small spines; dorsal face with numerous small spines or tubercles; ventral face weakly to strongly concave medially, with scattered small tubercles or spines. Merus with moderately dense and usually plumose setae; with scattered small tubercles on dorsal face; ventromesial margin with row of blunt to sharp spines; ventrolateral margin with row of small spines or tubercles. Ischium with ventromesial row of small, blunt spines. Coxa with ventromesial row of setae; ventral face with few small tubercles and ventrodistal row of small spines.

Left cheliped ( Fig. 40D ) usually weakly calcified on 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 slightly longer than length of mesial margin of palm. Palm unarmed except for dorsomesial row of small spines and scattered tufts of setae; ventral face smooth. Carpus with dorsodistal and dorsolateral spines; dorsal margin with long setae and row of small spines; ventral face smooth. 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. 41A–D ) similar right from left except for longer meri on right, extending to about tip of dactyls of right cheliped or slightly exceeding them. Dactyls ( Fig. 41B, D ) 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 about 4–6 minute spinules on ventromesial margin. Propodi each with sparse setae on dorsal margin; ventral margin with few setae. Carpi with few setae, each with small dorsodistal spine; dorsal margin unarmed or occasionally with 1 or 2 minute spines proximally. Meri unarmed or occasionally in larger specimens (sl> 2.5 mm) with row 2 or 3 small, well-spaced spines on dorsal margin ( Fig. 41C ). Ischia with small dorsodistal tufts of setae, and ventrodistal row of setae. Coxae with 1 or 2 small spines ventrodistally, and ventromesial row of setae. Anterior lobe of sternite XII (between second ambulatory legs, Fig. 38D ), setose, with subdistal blunt or sharp spine.

Fourth pereopod ( Fig. 41E ) 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. 41F ) semichelate. Propodal rasp extending to 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 and telson markedly asymmetrical. Telson ( Fig. 38E ) lacking transverse suture; dorsal surface with scattered setae; lateral margins with long setae distally; posterior lobes separated by shallow unarmed, U-shaped cleft; terminal margin of left lobe armed with about 12 mostly long and often strongly curved corneous spines, terminal margin of right lobe armed with about 6 small spines.

Male lacking first gonopods, with paired second gonopods. Second gonopod ( Fig. 38F ) flat, distal segment with long setae distally, proximal segment with long setae distomesially. Females with vestigial second right pleopod.

Variations. There is considerable variation in the shape and strength of armature of the carpus and chela of the right cheliped. The carpus varies from broader than long (about 1.1 as broad as long, Fig. 40C ) to distinctly longer than broad (about 1.2 times as long as broad, Fig. 40A ). The spines on the dorsolateral margin of the carpus and palm vary in strength; the dorsolateral margin of the palm is often sharply delimited by row of strong, distally upturned spines ( Fig. 40C ). The ventral surface of the right chela is somewhat variable, but generally the palm has a Y-shaped, median tuberculate ridge which branches towards the dactyl and the ventromesial angle of the palm; the median ridge can have a moderate to strong concave area.

Colouration ( Fig. 53E, F ). In life, light orange overall, with darker orange tone on dorsal surfaces of carpi of chelipeds and on dorsal surfaces of segments of ambulatory legs. Preserved specimens (at least about 5 years after fixation), although pale orange overall, stand out by the presence of a darker orange tone on the dorsal surfaces of the carpi of the right and left chelipeds, and on the dorsal faces of meri, carpi and propodi of the ambulatory legs.

Habitat. Gastropod shells.

Distribution. Known only from the south Pacific, in the Marquesas and the Austral Islands, French Polynesia. Depth: 90–1000 m.

Remarks. This new species is one of eight in Oncopagurus in which the antennal acicles are short, not exceeding the distal margin of the corneas; the others are: O. curvispina , O. bifidus , new species, O. glebosus , O. minutus , and four new species described herein, O. brevis , new species, O. elongatus , new species, and O. spiniartus , new species. Oncopagurus rossanae , new species can be separated most readily from those other congeners with short antennals acicles, by the Y-shaped tuberculate ridge on the ventral face of the palm of the right cheliped.

Oncopagurus rossanae , new species is one of eight Oncopagurus species in which males lack first gonopods (see Remarks under O. cidaris ). Of those eight, O. rossanae , new species, and two other new species described herein, O. bifidus and O. brevis , have short antennal acicles.

The size of adult specimens of this new species is quite small, varying in shield length from 1.1–3.3 mm, although the majority of the specimens are less then 2.0 mm.

Etymology. The name of this species is dedicated to my wife, Rossana, who for nearly four decades has encouraged my discoveries as well as accompanied me in every facet of my life.

Figures

Fig. 38. Oncopagurus rossanae, new species, A, C–D, holotype, male 2.9 mm, French Polynesia, Austral Islands, BENTHAUS, sta DW 1973 (MNHN-IU-2013-6869); B, paratype, male 2.4 mm, Marquesas Islands, MUSORSTOM 9, sta DW 1146 (USNM 1207996, ex MNHN Pg 6422); F, paratype, male 3.0 mm, same station as holotype (MNHN Pg 7032): A, B, shield and cephalic appendages; C, right antennal peduncle, lateral; D, anterior and posterior lobes of sternite XII (between second ambulatory legs), ventral; E, telson, dorsal; F, left second gonopod, anterior. Scale bars = 0.5 mm.

Fig. 39. Oncopagurus rossanae, new species, paratype, male 3.0 mm, French Polynesia, Austral Islands, BENTHAUS, sta DW 1973 (MNHN Pg 7032). Left mouthparts, internal: A, distal half of mandible; B, maxillule; C, maxilla; D, first maxilliped; E, second maxilliped; F, third maxilliped. Scale bars = 0.25 mm (A–D), 0.5 mm (E, F).

Fig. 40. Oncopagurus rossanae, new species, A, B, D, holotype, male 2.9 mm, French Polynesia, Austral Islands, BENTHAUS, sta DW 1973 (MNHN-IU-2013-6869); C, paratype female 2.0 mm, French Polynesia, Austral Islands, BENTHAUS, sta DW 1905 (USNM 1207998, ex MNHN Pg 6692): A, right cheliped, dorsal; B, chela of same, ventral; C, carpus and chela of right cheliped, dorsal; D, left cheliped, dorsal. Scale bars = 1 mm (A, B, D); 0.5 mm (C).

Fig. 41. Oncopagurus rossanae, new species, holotype, male 2.9 mm, French Polynesia, Austral Islands, BENTHAUS, sta DW 1973 (MNHN-IU-2013-6869): A, right first ambulatory leg, lateral; B, dactyl of same, mesial; C, right second ambulatory leg, lateral; D, dactyl of same, mesial; E, propodus and dactyl of left fourth pereopod, lateral; F, propodus and dactyl of left fifth pereopod, lateral. Scale bars = 1 mm, (A–D); 0.25 mm (E, F).

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

Fig. 53. Colouration in species of Oncopagurus (in life or fresh, except where noted). A, O. indicus (Alcock, 1905): Taiwan, TAIWAN 2003, sta CP 214: female 4.6 mm (NTOU). B, C, O. monstrosus (Alcock, 1894): B, [not sexed or measured], Taiwan (NTOU); C, male 3.6 mm, TAIWAN 2004, sta CP 269 (NTOU). D, O. orientalis (de Saint Laurent, 1972): male 3.6 mm, Taiwan, TAIWAN 2004 (MNHN Pg). E, F, O. rossanae, new species, French Polynesia, BENTHAUS: E, paratype male 2.5 mm, sta DW 1905 (MNHN Pg 6692); F, holotype M 2.9 mm, sta DW 1973 (MNHN-IU-2013-6869). G, O. tuamotu (Lemaitre, 1994): [not sexed or measured], French Polynesia, Moorea (UF). (Photographs by: Tin-Y. Chan [A–D]; Joseph Poupin [E, F]; Gustav Paulay [G]).