Pagurixus carinimanus, Komai & Osawa, 2006

Komai, Tomoyuki & Osawa, Masayuki, 2006, A review of the Pagurixus boninensis species group, with descriptions of six new species (Crustacea: Decapoda: Anomura: Paguridae), Zootaxa 1214 (1), pp. 1-107 : 71-79

Pagurixus carinimanus n. sp.

( Figs. 29–32 , 45B , 48 )

Pagurixus cf. tweediei .— McLaughlin & Haig, 1984: 134, fig. 4.— Rahayu, 2000: 394.— Paulay et al., 2003: 490.

Pagurixus sp. 3 (slate).— Paulay et al., 2003: 490.

Type material

HOLOTYPE: CBM­ZC 8479, male (SL 1.5 mm), Ankyaba , Amami­Oshima Island, Ryukyu Islands, 1 m, dead coral, coll. M. Osawa, 26 May 2003.

PARATYPES: CBM­ZC 2177, 1 male (SL 1.1 mm), Zanpa­misaki, Okinawa Island, Ryukyu Islands , 1–3 m, coll. E. Nishi, 30 April 1995 ; CBM­ZC 7871, 1 male (SL 1.8 mm), Ahra Beach, Kume­jima Island , intertidal, coll. T. Komai, 13 June 1995 ; CBM­ZC 8174, 1 ovigerous female (SL 1.6 mm), Urabishi fore reef, Kuroshima Island, Yaeyama Islands , 3–5 m, dead coral, coll. K. Nomura & T. Komai, 17 July 1999 ; CBM­ZC 8480, 1 female (SL 1.6 mm), Mizugama, Kadena, Okinawa Island , 1 m, lagoon, dead coral, coll. M. Osawa, 6 July 2000 ; CBM­ZC 8481, 1 female (SL 1.6 mm), Maeda­misaki, Okinawa Island , 3 m, SCUBA diving, coll. Y. Fujita, 28 July 2002 ; CBM­ZC 8482, 1 male (SL 1.6 mm), Maeda­misaki, Okinawa Island , 4.8 m, SCUBA diving, coll. Y. Fujita, 12 September 2002 .

Other material. Guam: UF 7299 , 3 males (SL 1.7–1.8 mm), 1 ovigerous female (SL 1.4 mm), Pago reef front, 4–8 m, under rubble in surge channels and pockets, coll. G. Paulay, 14 August 2000 , photo no. 860­16, 860­18; UF 7300 , 1 female (SL 1.1 mm), 1 ovigerous female (SL 1.3 mm), south of Haputo , 6–9 m, under rubble, coll . R. Chang et al., 16 August 2000 .

Description

Shield ( Fig. 29A ) 1.0–1.1 times as long as broad; anterior margin between rostrum and lateral projections slightly concave or almost straight; anterolateral margins sloping; dorsal surface with few tufts of short setae laterally. Rostrum triangular, reaching level of midlength of ocular acicles, terminating acutely. Lateral projections obsolete, with very small marginal or submarginal spinule.

Ocular peduncle ( Fig. 29A ) moderately long and stout, 0.6–0.7 length of shield, each with 1 or 2 short setae on dorsal surface mesially; corneas not dilated, corneal diameter 0.3–0.4 of peduncular length; middle part slightly inflated. Ocular acicles subtriangular, with small submarginal spinule.

Antennular peduncle ( Fig. 29A, B ) overreaching distal margin of cornea by 0.2–0.3 length of ultimate segments. Ultimate segment with tufts of long setae at dorsolateral distal angle; each setal row on ventral surface consisting of short transverse rows of short setae ( Fig. 29C ). Basal segment with small lateral spine on statocyst lobe. Ventral flagellum with numerous long setae on lateral and mesial margins.

Antennal peduncle ( Fig. 29A ) reaching or slightly overreaching distal margin of cornea. Second segment with small spine at dorsomesial distal angle; laterodistal projection reaching nearly to midlength of fourth segment, terminating in simple or bifid spine. First segment with small laterodistal spine; ventromesial distal margin produced, unarmed or armed with spinule just lateral to antennal gland opening. Antennal acicle moderately long, arcuate, overreaching base, but not reaching distal margin of cornea; mesial margin with few short stiff setae. Antennal flagellum moderately long, exceeding 3.0 length of shield.

Right cheliped of adult males ( Fig. 30A–C ) stout, not particularly elongate. Chela roundly subtriangular in dorsal view, 1.7–1.8 times longer than broad. Dactylus about 0.8 length of palm; dorsal surface with low, tuberculate ridge on midline, dorsomesial margin not delimited; surfaces covered with coarse granules; cutting edge with 2 triangular, calcareous teeth on proximal 0.7 and row of small corneous teeth on distal 0.3, terminating in small corneous claw. Palm shorter than carpus; convex dorsal surface covered with coarse granules, with or without median, nearly straight, faintly tuberculate keel, extending onto basal part of fixed finger, dorsolateral and dorsomesial margins each with distinct granular ridge; longitudinal row of small granules adjacent to dorsomesial margin, confluent with mid­dorsal ridge on dactylus, lateral, mesial and ventral surfaces coarsely granular, with few tufts of short setae on ventral surface. Cutting edge of fixed finger with row of small calcareous teeth, terminating in calcareous claw. Carpus subequal in length to merus; dorsal surface with 2 mesial rows of long bristles and short, low transverse ridges laterally, dorsolateral and dorsomesial margins not delimited; lateral and mesial faces with scattered granules, lateral surface lacking median longitudinal ridge. Meral­carpal articulation lacking any pronounced clockwise rotation; dorsal surface of merus nearly smooth with 1 low transverse ridge subdistally, dorsodistal margin unarmed; lateral face almost smooth, ventrolateral margin only with 1 small subdistal spine; mesial face also smooth, ventromesial margin unarmed; ventral surface unarmed, but with several long setae. Ischium with row of very small denticles on ventromesial margin, otherwise unarmed.

Right cheliped of female ( Fig. 31A–D ) and young male comparatively short for genus. Dactylus about 1.1 length of palm; dorsal surface with faint longitudinal ridge on midline, dorsomesial margin not delimited; surfaces almost smooth except for some small tubercles on dorsomesial surface; cutting edge with 1 low calcareous teeth in proximal half and row of small corneous teeth in distal half, terminating in small corneous claw. Palm shorter than carpus; dorsomesial margin with sharp, tuberculate ridge running over entire length; dorsal surface with median, nearly straight, faintly tuberculate keel, extending onto basal part of fixed finger, surface either side of median keel concave, almost smooth; dorsolateral margin elevated to form thin, unarmed keel, extending nearly to tip of fixed finger; mesial part of dorsal surface with longitudinal, tuberculate ridge confluent with median ridge on dactylus; lateral, mesial and ventral surfaces nearly smooth. Cutting edges of fixed finger with row of small, subacute teeth almost over entire length and few small corneous teeth subdistally, terminating in small corneous claw. Carpus subequal in length to merus; dorsal surface with 2 mesial rows of long bristles and low protuberances and with small tubercles and low protuberances laterally; dorsolateral and dorsomesial margins not clearly delimited; lateral and mesial faces with scattered, low granules, lateral surface with short, tuberculate, oblique ridge distally. Meral­carpal articulation lacking any pronounced clockwise rotation; dorsal surface of merus nearly smooth with 1 subdistal transverse ridge, dorsodistal margin unarmed; lateral face with scattered, low tubercles ventrally, otherwise smooth, ventrolateral margin with small subdistal tooth followed by small tubercles; mesial face smooth, ventromesial margin with row of small tubercles; ventral surface with several low tubercles and few long setae. Ischium unarmed on ventromesial margin.

Left cheliped relatively short, dimorphic. Chela of adult males ( Figs. 30D–F ) about 2.0–2.1 times longer than broad. Dactylus longer than palm, with few short setae on surfaces (setae on ventral surface longest); dorsal surface unarmed; cutting edge with row of small corneous teeth, terminating in small corneous claw. Palm about half length of carpus; dorsal surface somewhat elevated in midline, but not forming conspicuous keel, with small, simple or bifid tubercles medially and longitudinal row of small tubercles mesially; dorsolateral margin with sharp, weakly tuberculate keel extending to midlength of fixed finger, weakly expanded laterally; dorsomesial margin not delimited; lateral and mesial faces with faint tubercles or protuberances; ventral surface convex, with tufts of long setae. Cutting edge of fixed finger unarmed in proximal half, distal half with row of small subacute calcareous teeth and subdistal row of small corneous teeth, terminating in small corneous claw. Carpus moderately stout, somewhat compressed laterally, 0.8–0.9 length of chela and slightly longer than merus; length about 2.1 of distal width and 1.9 greatest height; dorsolateral and dorsomesial margins slightly delimited, each with row of low, small protuberances and short to long bristles; surfaces with few granules or very low protuberances; sparse long setae present on ventral surface; lateral surface perpendicular, lacking median longitudinal ridge. Merus with 1 subdistal transverse ridge extending onto mesial surface, otherwise smooth, dorsodistal margin with row of short stiff setae; lateral and mesial faces nearly smooth, ventrolateral margin with 1 or 2 subdistal spines followed by few low protuberances, ventromesial margin unarmed; ventral surface with several long setae. Ischium with smooth ventromesial margin, but occasionally with few bristles on distolateral margin.

Left chela of females ( Fig. 31E, F ) and small males with notably expanded dorsolateral keel; dorsal surface of palm with median, nearly straight, tuberculate keel, extending onto midlength of fixed finger, surface either side of median keel concave, almost smooth; mesial part of dorsal surface with longitudinal, faintly tuberculate keel confluent with median ridge on dactylus. Carpus and merus similar to those of adult males.

Ambulatory legs ( Fig. 32A, B, E ) comparatively short and stout for genus, second pereopods similar from right to left, third pereopods dissimilar with left appreciably broader and shorter than right. Dactyli of second and right third pereopods 0.9–1.0 length of propodi and 4.8–5.2 times longer than high, terminating in large corneous claws ( Fig. 32C, E ); dorsal surfaces each with row of sparse short setae; lateral and mesial faces faintly sulcate medially, each with few tufts of short setae, mesial faces unarmed; ventral margins each with 5–7 moderately long corneous spines notably increasing in size distally. Dactylus of left third pereopod ( Fig. 32D ) notably broadened, 0.9 length of propodi, 3.0–3.1 times longer than high; mesial surface flat, unarmed; ventral margin with 5–6 corneous spines. Propodi of second and right third pereopods not tapering distally, 3.0–3.1 times longer than high; dorsal surfaces each with row of low protuberances (second) or smooth (right third), and with short stiff setae or bristles; lateral faces smooth, slightly convex on second, slightly concave on right third; ventral margins each with 2–3 corneous spinules, ventrodistal margins each with paired corneous spines. Propodus of left third pereopod stout, 2.7–2.8 times longer than high; lateral face slightly concave, with row of tiny, simple or bifid tubercles on midline; armament and setation otherwise similar to propodi of other pereopods. Carpi each with tiny dorsodistal spine; dorsal surface smooth, but with row of short setae; lateral faces smooth, with few very short setae. Meri each with moderately long setae and/or short bristles on nearly smooth dorsal surface; lateral surfaces nearly smooth; ventrolateral distal margins each with small subdistal spine (second) or unarmed (third), ventral surfaces with few low protuberances (second) or smooth (third), all with sparse short to moderately long setae.

Fourth pereopods ( Fig. 29D–I ) markedly unequal in males and females and setation more pronounced on left than right. Dactyli terminating in large corneous claw, left broader than right, slightly twisted; dorsal margin of left dactylus with row of long stiff setae, that of right only with few short setae; mesial face of left propodus markedly elevated in midline and bearing several long setae; mesial face of right propodus nearly flat, naked.

Anterior lobe of sixth thoracic sternite ( Fig. 29J ) subrectangular, anterolateral angles rounded, anterior margin with row of short setae. Eighth thoracic sternite ( Fig. 29K ) composed of two markedly unequal, narrowly separated, rounded lobes (right lobe larger than left).

Males with coxae of fifth pereopods slightly unequal ( Fig. 29K ). Right coxa with tuft of long stiff setae directed toward midline and reaching to left coxa; coxal protrusion absent, papilla­like protrusion of vas deferens occasionally apparent. Left coxa with papilla­like protrusion arising from gonopore; several short setae present. Female with unpaired left gonopore.

Telson ( Fig. 29L ) with terminal margins rounded, faintly denticulate or with 3 or 4 very small spinules.

Variation. Sexual dimorphism in shape and ornamentation of the chelipeds is appreciable in P. carinimanus . Female and small male specimens have sharply carinate dorsolateral and dorsomesial margins and two sharp dorsal keels on the right and left palms. These carinae or keels are reduced or rudimentary in large male specimens. In particular, the median keel on the right palm found in female and small males becomes indistinguishable in large males.

Colour in life. ( Fig. 45B ) Shield generally cream, anteriorly with 2 light brown patches on either side of midline. Ocular peduncles each with 2 short, reddish brown longitudinal stripes, 1 on dorsolateral surface and another on dorsomesial surface. Antennal peduncles generally cream, second segment with tinge of brown on dorsal surface. Right cheliped with palm and carpus light reddish brown to dark purplish brown; merus banded by white and brown. Ambulatory legs generally white or light gray, banded by dark, occasionally reddish, brown; dactyli each with brown band in proximal 0.2; propodi white in distal 0.3–0.4, remainder brown, proximal brown band bordered dorsally by darker, reddish brown stripe; carpi banded by alternating 2 white and 2 brown bands from distal to proximal, connected by longitudinal stripe on dorsolateral face; meri also banded by alternating 2 brown and 2 white bands from distal to proximal bands; ischia with 1 reddish brown patch on dorsal surface.

Distribution Ryukyu Islands, Guam and the Philippines ( Fig. 48 ); 1– 15 m.

Remarks

Pagurixus carinimanus n. sp. is unique among the species of Pagurixus treated in this study in the appreciably dissimilar third pereopods and the quadricarinate right chelae in females and small males. Although the keels or ridges of the chelae are reduced in males, large males of P. carinimanus n. sp. can be distinguished from males of all other species of the P. boninensis group in the right palm having a clearly delimited dorsomesial margin and a distinct longitudinal row of granules adjacent to the dorsomesial margin.

McLaughlin & Haig (1984) diagnosed a species tentatively assigned to P. tweediei from the Philippines, and noted some differences that they attributed to intraspecific variation. Reexamination of the syntypes of P. tweediei has shown that McLaughlin & Haig’s Philippine specimen is significantly different from P. tweediei in lacking the lateral longitudinal ridge on the carpus of the left cheliped, a feature present in P. tweediei . McLaughlin & Haig’s diagnosis agrees well with our male specimens of P. carinimanus particularly in the right chela having crenulate dorsolateral and dorsomesial margins and two rows of granules on the dorsal surface. Rahayu (2000) gave a list of hermit crabs recorded from the South China Sea based on literature. She cited P. cf. tweediei based on the record of McLaughlin & Haig (1984).

Reexamination of the specimens from Guam ( UF 7299, 7300) has revealed that

Pagurixus sp. 3 (slate) of Paulay et al. (2003) corresponds to Pagurixus carinimanus n. sp.

Etymology

Derived from the Latin carina, meaning’ keel’, and manus, meaning ’hand’, in reference to the characteristic keels of the chelae in females and small males.

Figures

FIGURE 29. Pagurixus carinimanus n. sp. A–E, J–L, holotype male (SL 1.5 mm) from Amamioshima Island (CBM­ZC 8479); F–I, paratype female (SL 1.6 mm) from Okinawa Island (CBM­ZC 8480). A, shield and cephalic appendages, dorsal view; B, left antennule, lateral view; C, ultimate segment of left antennular peduncle, ventral view; D, F, left fourth pereopod, dactylus and propodus, lateral view; E, G, same, mesial view; H, right fourth pereopod, dactylus and propodus, lateral view; I, same, mesial view; J, sixth thoracic sternite, ventral view; K, coxae of fifth pereopods and eighth thoracic sternite, ventral view; L. telson, dorsal view. Scale bars: 0.5 mm.

FIGURE 30. Pagurixus carinimanus n. sp. Holotype male (SL 1.5 mm) from Amami­oshima Island (CBM­ZC 8479). A, right cheliped, chela and carpus, dorsal view; B, entire right cheliped, mesial view; C, same, lateral view; D, left cheliped, chela and carpus, dorsal view; E, entire left cheliped, mesial view; F, same, lateral view. Scale bar: 0.5 mm.

FIGURE 31. Pagurixus carinimanus n. sp. Paratype female (SL 1.6 mm) from Okinawa Island (CBM­ZC 8480). A, chela of right cheliped, dorsal view; B, entire right cheliped, mesial view; C, same, lateral view; D, carpus of right cheliped, dorsal view; E, chela of left cheliped, dorsal view; F, same, lateral view. Scale bar: 0.5 mm.

FIGURE 32. Pagurixus carinimanus n. sp. Holotype male (SL 1.5 mm) from Amami­oshima Island (CBM­ZC 8489). A, right second pereopod, lateral view; B, left third pereopod, lateral view; C, right second pereopod, dactylus and distal part of propodus, mesial view; D, left third pereopod, dactylus and distal part of propodus, mesial view; E, right third pereopod, dactylus and propodus, lateral view. Scale bars: 0.5 mm.

FIGURE 45. A, Pagurixus boninensis (Melin, 1939), ovigerous female (SL 2.7 mm) from Hachijo Island, Izu Islands, Japan (CMNH­ZC 1688), photo taken by J. Okuno; B, Pagurixus carinimanus n. sp., paratype female (SL 1.6 mm) from Okinawa Island, Ryukyu Islands (CBM­ZC 8481), photo taken by Y. Fujita; C, D, Pagurixus brachydactylus n. sp., male (SL 2.6 mm) from Chichi­jima Island, Ogasawara Islands, photo taken by M. Osawa.

FIGURE 48. Geographic distribution of Pagurixus boninensis (), P. festinus (), P. brachydactylus n. sp. (), P. carinimanus n. sp. (), P. paulayi n. sp. (Π), P. pseliophorus n. sp ()., and P. ruber n. sp. ().