Oncopagurus monstrosus ( Alcock, 1894 )

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 : 261-265

Oncopagurus monstrosus ( Alcock, 1894)

Figs. 28 , 51 , 53B, C

“? Parapagurus monstrosus ” Alcock, 1894: 243 (type locality, by lectotype designation: Bay of Bengal ).

Sympagurus monstrosus – Henderson, 1896: 533; Alcock & Anderson, 1897, pl. 32, fig. 4; Alcock, 1901: 223; Lemaitre, 1989: 37; 1994: 412.

Sympagurus arcuatus var. monstrosus – Alcock, 1905: 104, pl. 10, fig. 5; Gordan, 1956: 341; Kemp & Sewell, 1912: 26.

Parapagurus monstrosus – de Saint Laurent, 1972: 108; Miyake, 1978: 72 (key); 1982: 119, pl. 40, fig. 1; Baba et al., 1986: 302, fig. 146; Imafuku, 1992: 234, unnumbered fig.

Oncopagurus monstrosus – Lemaitre, 1996: 199 , figs. 19, 20; 1997: 594; Spiridonov & Zhadan, 1999: 625, fig. 1; Zhadan, 1997: 63 (table); Zhadan, 1999: 737; Rahayu, 2000: 396; McLaughlin, 2002: 450; Davie, 2002: 89; Asakura et al., 2006: 211, fig. 2; McLaughlin et al., 2007: 315, unnumbered figs. a–d; McLaughlin et al., 2010: 2010: 39, fig. 19A.

Oncopagurus indicus – McLaughlin et al., 2007: 313, unnumbered colour photo (sta DW 56) (See Remarks).

(For complete synonymy see Lemaitre, 1996)

Type material. Lectotype, Indian Ocean , Bay of Bengal [probably from RIMSS Investigator, sta 120, 15°56'50"N, 81°30'30"E, 439 m, 24 December 1890]: M 4.2 mm ( USNM 156566 )

Paralectotypes: 2 M 3.4, 3.7 mm, same sta data as lectotype ( USNM 156566 ) .

Additional material. Japan: Tosa Bay, 275 m, 9 April 1985, coll. M. Toriyama: 4 M 4.3–6.1 mm, 1 ov F 4.5 mm ( USNM 1211227 ); Shionomisaki, Kii Peninsula , 200 m, 4 March 1991, coll. S. Nagai: 1 M 5.2 mm ( USNM 276119 ) . Taiwan: TAIWAN 2004: sta CP 269, 24°30.55'N, 122°5.78'E, 399– 397 m, 9 February 2004: 3 M 2.4–3.6 mm ( MNHN Pg.) . Philippines: Siboga Expedite , sta 212, 05°54.5'S, 120°19.2'E, 462 m, 19 September 1899: 1 M 2.0 mm ( MNHN Pg. 3203) . — Th. Mortensen′ s Pacific Expedition 1913–1916: 3 miles SW of Tucuran, 550 m, 10 March 1914: 1 M 1.5 mm, 1 F 2.2 mm ( ZMK); 25 miles E of S. Zamboanga, 665– 290 m, 3 March 1914: 1 M 3.9 mm ( ZMK) — MUSORSTOM 2 : sta CP 40, 13°08'N, 122°39'E, 280–340 m, 25 November 1980 (2 lots): 9 M 3.2–4.8 mm ( MNHN Pg.), 1 M 3.8 mm ( MNHN Pg.); sta CP 49, 13°38'N, 121°44'E, 416–425 m, 26 November 1980: 3 M 3.5–5.5 mm ( MNHN Pg.); sta CP 64, 14°01'N, 120°19'E, 191–195 m, 29 November 1980: 1 F 2.4 mm ( MNHN Pg.) — MUSORSTOM 3: sta CP 108, 14°01'S, 120°18'E, 188–195 m, 2 June 1985: 1 F 3.0 mm ( MNHN Pg.); sta CP 138, 11°54'S, 122°15'E, 252–370 m, 6 June 1985: 1 M 3.7 mm, 1 F 2.2 mm ( MNHN Pg.) . Indonesia: Den danske Kei Eksped. 1922: sta 50, 05°34'S, 132°25'40"E, 233 m, 4 May 1922: 1 M 2.1 mm ( ZMK); sta 63, 05°32'S, 132°36'25"E, 250 m, 16 May 1922: 1 F 2.2 mm ( ZMK) — Th. Mortensen′ s Pacific Expedition 1913–1916: sta 7, 08°29'S, 114°40'E, 200 m, 5 April 1929: 1 M 3.9 mm ( ZMK); sta 15, 07°29'S, 114°49'E, [no depth], 10 April 1929: 1 F 2.0 mm ( ZMK) . Solomon Islands: SALOMON 1: sta CP 1747, 9°21.8'S, 159°58.7'E, 364–402 m, 25 September 2000 (2 lots): 3 M 4.2–4.8 mm, 1 F 4.1 mm ( MNHN Pg.), 6 M 3.2–4.4 mm, 5 F 2.7–4.7 mm, 1 ov F 3.1 mm ( MNHN Pg.); sta CP 1786, 9°21.3'S, 160°24.6'E, 387 m, 30 September 2000: 2 M 4.2, 4.7 mm, 2 F 3.0, 3.8 mm, 1 ov F 3.7 mm ( MNHN Pg.); sta CP 1800, 9°21.4'S, 160°23.9'E, 357–359 m, 1 October 2000 (3 lots): 1 M 4.7 mm ( MNHN Pg.), 1 M 5.2 mm ( MNHN Pg.), 8 M 2.4–4.3 mm, 3 F 1.8–2.9 mm ( MNHN Pg.); sta CP 1804, 9°32.0'S, 160°37.4'E, 309–328 m, 2 October 2000: 3 M 3.6–4.8 mm, 2 ov F 3.6, 4.0 mm ( MNHN Pg.) — SALOMON 2: sta CP 2262, 7°57.5'S, 156°51.346'E, 460–487 m, 11 March 2004: 1 M 5.5 mm ( MNHN Pg.) . Tonga Islands : BORDAU 2: sta CP 1593, 19°06'S, 174°18'W, 436–442 m, 14 June 2000: 1 M 3.1 mm ( MNHN Pg. 6504) . New Caledonia: BIOCAL: sta DW 33, 23°09.71'S, 167°10.27'E, 675 m, 29 August 1985: 1 M 2.1 mm, 2 F 2.0, 3.2 mm ( USNM 1211228 ) — MUSORSTOM 4: sta CC 175, 18°59.30'S, 163°17.50'E, 370 m, 17 September 1985: 1 M 2.7 mm, 1 ov F 2.1 mm ( USNM 1211229 ) — CHALCAL 2: sta DW 73, 24°39.90'S, 168°38.10'E, 573 m, 29 October 1986: 5 M 3.0– 3.3 mm, 2 F 2.0, 2.4 MM, 1 ov F 1.9 mm ( USNM 1202681 ) — BATHUS 1: sta CP 695, 20°34.59'S, 164°57.88'E, 410–430 m, 17 March 1993: 1 M 1.5 mm, 2 F 1.7, 1.9 mm, 1 ov F 1.5 mm ( MNHN Pg.) — BATHUS 3: sta DW 838, 23°00.81'S, 166°55.87'E, 400–402 m, 30 November 1993: 2 F 1.8, 2.3 mm ( MNHN Pg.) — BATHUS 4: sta CP 950, 20°31.93'S, 164°56.11'E, 705–750 m, 10 August 1994: 1 M 3.1 mm ( MNHN Pg.) —NORFOLK 2: sta DW 2074, 25°24.01'S, 168°19.96'E, 623–691 m, 27 October 2003: 4 M 2.4–2.8 mm ( MNHN Pg.); sta DW 2080, 25°20.40 S, 168°18.74 E, 764–816 m, 27 October 2003: 1 M 4.0 mm ( MNHN Pg.) .

Diagnosis. Shield ( Fig. 28A ) about as long as broad; rostrum broadly rounded, with low mid–dorsal ridge; lateral projections broadly subtriangular, usually terminating in small spine. Ocular peduncles more than half length of shield; ocular acicles subtriangular, terminating in strong spine; corneas dilated. Antennular peduncle ( Fig. 28A ) exceeding distal margin of corneas by full length of ultimate segment. Antennal peduncle ( Fig. 28A ) exceeding distal margin of cornea by at most 0.3 length of fifth segment; fourth segment with small spine on dorsolateral distal angle; second segment with dorsolateral distal angle terminating in strong spine; acicles at most slightly exceeding distal margin of corneas, mesial margin armed with 8–15 spines; flagellum with series of short (<1 article in length) and long (> 3 articles in length) setae every 8–20 articles. Third maxilliped with crista dentata of about 10–13 teeth, proximal teeth lager than distal. Right cheliped ( Fig. 28B–G ) with moderately dense setae, chela operculate, chela proportions influenced by sex, less than twice as long as broad in males, or about as long as broad in females; palm with irregular rows of small spines medially on dorsal face, dorsolateral and dorsomesial margins well delimited by row of small spines; mesial face of palm rounded, with small spines or tubercles. Left cheliped with dorsolateral face of carpus often weakly calcified; palm unarmed except for few setae; carpus with dorsodistal spine. Ambulatory legs with dactyls ( Fig. 28H ) each having ventromesial row of about 5–15 small corneous spinules; carpus with small dorsodistal spine. Anterior lobe of sternite XII (between second ambulatory legs) with small subterminal spine, setose. Fourth pereopod propodal rasp ( Fig. 28I ) with 1 row of ovate scales at least distally. Uropods and telson markedly asymmetrical; telson ( Fig. 28J ) lacking transverse suture, posterior lobes separated by U-shaped median cleft, terminal margins armed with often strongly curved corneous spines. Males with paired first and second gonopods ( Fig. 28K, L ); first gonopod with weakly concave distal lobe; second gonopod with distal segment nearly flat, setose distally. Females with vestigial right second pleopod.

Colouration ( Fig. 53B, C ). Carapace light orange. Right cheliped with chela and distal 0.6 of carpus creamy-white; carpus with orange-red portion on proximal third of dorsal surface; merus dorsal surface orange-red on proximal 0.6 of dorsal surface, creamy-white distally. Left cheliped creamywhite with reddish-orange patches on lateral faces of merus, carpus and propodus. Ambulatory legs with carpi and propodi each with two orange-reddish patches on mesial and lateral faces; meri with orange-reddish patches on dorsal surface that are often partially fused and extended to lateral and mesial surfaces. [See also Miyake (1982: 118, pl. 40, fig. 1), Baba et al. (1986: 146, pl. 302), Imafuku (1992: 234), and McLaughlin et al. (2007: 313, as O. indicus )].

Habitat. Gastropod shells usually with actinian attached to shell.

Distribution. Indo-Pacific: Gulf of Aden; Bay of Bengal; Japan; Taiwan; Philippines; Indonesia; Solomon Islands; Tonga Islands; New Caledonia; and Australia. Depth: 188–1000 m.

Remarks. As previously mentioned, Oncopagurus monstrosus is similar to O. indicus , and often the two are difficult to separate (see Remarks under O. indicus ). Individuals of O. monstrosus grow to a larger size, reaching 6 mm or more in sl, whereas specimens of O. indicus rarely exceed 3 or 4 mm in sl. Aside from characters of the right cheliped as discussed under O. indicus , the greater development of ocular peduncles and corneas in O. monstrosus can also serve to distinguish the two species. To a lesser degree, because of some variability, the armature of the merus of the right second ambulatory leg, can also serve to distinguish the two species. In O. monstrosus the merus lacks spines dorsally, whereas a row of several small spines is usually present on the merus in O. indicus .

Colour differences between Oncopagurus monstrosus and O. indicus are discussed under the latter species.

Oncopagurus oimos Lemaitre, 1998 Figs. 29 , 51

Oncopagurus oimos Lemaitre, 1998: 102 , figs 1–3 (type locality: Tuamotu Archipelago, Moruroa atoll, French Polynesia, FRV Marara, sta 499, 21°47.6'S, 138°55.7'W); McLaughlin et al., 2010: 2010: 39.

Type material. Holotype, French Polynesia, Tuamotu Archipelago, Moruroa atoll, R/ V Marara, sta 499, 21°47.6'S, 138°55.7'W, 200 m, 5 May 1996: M 2.8 mm ( MNHN Pg. 5505).

Paratypes, same locality as holotype: 1 M 2.4 mm, 1 F 2.7 mm ( MNHN Pg. 5506); 1 M 2.9 mm ( USNM 276085 ) .

Additional material. None found since original description.

Diagnosis. Shield ( Fig. 29A ) as broad as long; lateral projections subtriangular, terminating in small spine. Rostrum broadly rounded, weakly produced, with short mid-dorsal ridge. Ocular peduncles more than half length of shield, with dorsal row of short setae; cornea weakly dilated. Ocular acicles subtriangular, terminating in short spine. Antennular peduncle ( Fig. 29A ) exceeding distal margin of cornea by entire length of ultimate segment. Antennal peduncle ( Fig. 29A ) exceeding distal margin of cornea by about 0.3 length of fifth segment; fourth segment with strong spine on dorsolateral distal angle; second segment with dorsolateral distal angle terminating in strong, simple spine, mesial margin with spine on dorsodistal angle; first segment with unarmed lateral face; acicle at most slightly exceeding distal margin of cornea, mesial margin with 8–13 spines. Third maxilliped with crista dentata armed with about 12 teeth, proximal teeth larger than distal. Right cheliped ( Fig. 29B, C ) massive, chela operculate; dactyl set at strongly oblique angle to longitudinal axis of palm, with ventromesial face concave; palm broader than long, dorsal surface smooth except for scattered small spines or tubercles, lateral margin well delimited by row of blunt to sharp small spines, dorsomesial margin with row of small spines or tubercles, mesial face rounded, ventral surface smooth; carpus with lateral margin well delimited by row of small spines, dorsal surface with numerous small spines or tubercles. Left cheliped usually well calcified, carpus long (up to 4 times as long as broad), unarmed dorsally except for strong dorsodistal spine. Ambulatory legs ( Fig. 29D, E ) with dactyls ( Fig. 29F ) each armed with 10–14 small corneous spinules, carpi unarmed dorsally except for small dorsodistal spine. Anterior lobe of sternite XII (between second ambulatory legs) subsemicircular, setose, with distinct spine. Fourth pereopod propodal rasp ( Fig. 29G ) with 1 row (at least distally) of rounded scales. Fifth pereopod propodal rasp extending to midlength of segment. Uropods and telson markedly asymmetrical; telson ( Fig. 29H ) lacking transverse suture, posterior lobes separated by shallow unarmed, U-shaped cleft, terminal margins of lobes with about 13 corneous spines (left lobe) and 4 small corneous spines (right lobe). Male lacking first gonopods, with unpaired reduced second gonopod ( Fig. 29I, J ) consisting of minute bud or short segment. Female lacking vestigial second right pleopod.

Colouration. After approximately one year in alcohol, shield with two small reddish spots on anterior half, one just behind each lateral projection. On both chelipeds, dorsodistal portions of the meri reddish. Carpus of right cheliped with reddish area on proximal portion of lateral and mesial faces. Carpus of left cheliped with distinctive broad reddish stripe on dorsolateral and mesial faces; dorsomesial margin of palm light reddish; dactyl reddish. Ambulatory legs (Fig.) with reddish colour dorsodistally on meri; carpi each with reddish stripe on lateral and mesial faces, stripes of carpi continue on meri but only on lateral faces; dactyls with reddish dorsal faces (from Lemaitre, 1998).

Habitat. Gastropod shells.

Distribution. So far known exclusively from the type locality in Moruroa atoll, on the Tuamotu Archipelago, French Polynesia. Depth: 200 m.

Remarks. As previously mentioned, Oncopagurus oimos , is one of eight species of Oncopagurus in which males lack first gonopods (see Remarks under O. cidaris ). The degree of development of the second gonopods, however, differs in these eight species. The second gonopods can be symmetrical ( O. elevatus , new species, O. rossanae , new species), or asymmetrical and 1-segmented or 2-segmented ( O. cidaris , O. haigae , O. orientalis , O. bifidus , new species, O. brevis , new species). The right second gonopod varies, and can be vestigial or altogether absent ( O. oimos , O. cidaris , O. orientalis , O. bifidus , new species).

Among Oncopagurus species that occur in the French Polynesia region, O. oimos is closest morphologically to O. tuamotu . The two species can be separated based on the armature of the mesial face of the right palm, which is rounded in O. oimos or at most with a weak dorsomesial row of small spines, whereas the mesial face is expanded distally and there is a distinct dorsomesial and ventromesial rows of spines in O. tuamotu . Males of O. oimos have reduced, unpaired second gonopod (left gonopod only), whereas the second gonopods are paired and 2–segmented in O. tuamotu . The left chela in O. oimos is noticeably more slender, as long as the carpus, and the fingers are set nearly parallel to the longitudinal axis of the palm, whereas the chela is shorter than the carpus, and the fingers are set obliquely (pointing ventrolaterally) to the longitudinal axis of the palm in O. tuamotu . The colour pattern (at least in preserved specimens) of O. oimos is distinctive in having a broad orangish stripe that extends from the distal part of the merus to near the dactyl claw of each of the ambulatory legs ( Fig. 29D, E ).

Figures

Fig. 28. Oncopagurus monstrosus (Alcock, 1894): A–D, H–L, lectotype, male 4.2 mm, Bay of Bengal (USNM 156566); E, female 3.4 mm, Indonesia (USNM 168939); F, male 4.2 mm, Indonesia (USNM 168940); G, male 5.1 mm, Philippines (USNM 168931). A, shield and cephalic appendages, dorsal; B, carpus and chela of right cheliped, dorsal; C, D, chela of same, lateral (C), mesial (D); E, right cheliped of female, dorsal; F, G, chela of male, ventral; H, dactyl of right first ambulatory leg, mesial; I, propodus and dactyl of left fourth pereopod, lateral; J, telson, dorsal; K, left first gonopod, mesial; L, left second gonopod, anterior. Scale bars = 1 mm (A, H); 2 mm (B–G); 0.5 mm (I–L). [Adapted from Lemaitre (1996)].

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]).

Fig. 29. Oncopagurus oimos Lemaitre, 1998, holotype, male 2.8 mm, French Polynesia, Moruroa atoll (MNHN Pg 5505). A, shield and cephalic appendages, dorsal; B, right cheliped, dorsal; C, chela of same, ventral; D, first left ambulatory leg, lateral; E, second left ambulatory leg, lateral; F, dactyl of same, mesial; G, propodus and dactyl of left fourth pereopod, lateral; H, telson, dorsal; I, left second gonopod, lateral; J, left second pleopod, lateral. Scale bars = 1 mm (A–E), 0.5 mm (F–H, I, J). [Adapted from Lemaitre (1998)].