Pagurixus pseliophorus, 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 : 85-92

Pagurixus pseliophorus n. sp.

( Figs. 36–40 , 46A , 48 )

Type material

HOLOTYPE: CBM­ZC 7856, male (SL 2.8 mm), Ahra beach, Kume­jima Island, Ryukyu Islands, intertidal reef flat, coll. K. Nomura, 15 June 1995.

PARATYPES: CBM­ZC 7857, 2 females (SL 2.1, 2.2 mm), same data as holotype; CBM­ZC 7858, 1 female (SL 4.2 mm), Hane­misaki , Kochi Prefecture, intertidal, coll. S. Wada, 26 April 2001 ; CBM­ZC 8533, 1 male (SL 3.3 mm), Saga, Kochi Prefecture, 0–1 m, coll. H. Matsui, 23 July 2005 ; CMNH­ZC 1874 , 1 male (SL 3.4 mm), Akino­hama, Izu­oshima Island, Izu Islands , 2 m , SCUBA diving, coll. H. Arima, 29 January 2005 ; CMNH­ZC 1876 , same locality, coll. H. Arima, 1 March 2005 ; CMNH­ZC, 2 ovigerous females (SL 2.8, 4.3 mm), same locality, coll. H. Arima & J. Okuno, 11 July 2005 .

Description

Shield ( Fig. 36A ) 1.2–1.3 times longer than broad; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin truncate; dorsal surface with few tufts of short setae laterally. Rostrum triangular, distinctly overreaching lateral projections, moderately slender, terminating acutely or roundly. Lateral projections obtusely triangular, moderately produced, with submarginal spinule.

Ocular peduncle ( Fig. 36A ) moderately long and comparatively slender, 0.6–0.8 length of shield, each with row of tufts of short setae on dorsomesial surface; corneas slightly dilated, corneal width 0.25–0.3 of peduncular length; basal part slightly inflated, subequal to corneal width. Ocular acicles subtriangular, each with small submarginal spine.

Antennular peduncle ( Fig. 36A, B ) reaching or slightly overreaching distal margin of cornea. Ultimate segment with tufts of long setae at dorsolateral distal angle; each setal row on ventral surface consisting of single row of comparatively long setae directed laterally ( Fig. 36C ). Basal segment with small lateral spine on statocyst lobe. Ventral flagellum with numerous long setae on lateral and mesial margins.

Antennal peduncle ( Fig. 36A ) just reaching distal margin of cornea. Second segment with very small spine at dorsomesial distal angle; laterodistal projection short, not reaching midlength of fourth segment, terminating in simple or bifid spine. First segment with small laterodistal spine; ventromesial distal margin produced, unarmed or with spinule just lateral to antennal gland opening. Antennal acicle short, arcuate, slightly falling short of base of cornea; mesial margin with row of short stiff setae. Antennal flagellum moderately long, exceeding 3.0 length of shield.

Right cheliped of males ( Fig. 37A–D ) not particularly elongate, comparatively stout. Chela subovate in dorsal view, about 1.7 times longer than broad. Dactylus about 0.6 length of palm; dorsomesial margin not delimited; surfaces coarsely granular; cutting edge with row of small calcareous teeth, terminating in very small corneous claw. Palm subequal in length to carpus; convex dorsal surface microscopically granular, dorsolateral margin faintly delimited (including fixed finger), dorsomesial margin not delimited; lateral, mesial and ventral surfaces also microscopically granular. Cutting edge of fixed finger with 1 large calcareous tooth at midlength and row of small calcareous teeth in distal half, terminating in calcareous claw. Carpus subequal in length to merus; dorsolateral and dorsomesial margins not delimited; all surfaces microscopically granular, lateral surface lacking median longitudinal ridge; ventral surface notably convex. Meralcarpal articulation lacking any pronounced clockwise rotation; dorsal surface of merus with row of very low transverse ridges and few proximal tufts of short setae, dorsodistal margin with row of short setae; lateral face microscopically granular, with very small tubercles adjacent to ventrolateral margin, ventrolateral margin with row of small spines; mesial face smooth, with scattered long stiff setae, ventromesial margin with row of small tubercles; ventral surface with scattered granules and long setae. Ischium with smooth ventromesial margin; surfaces unarmed.

Right cheliped of females ( Fig. 38A–D ) moderately stout for genus. Chela subovate in dorsal view, 1.8–1.9 times longer than broad. Dactylus slightly longer than palm; dorsal surface with longitudinal row of granules on midline, mesial face with short row of granules; ventral surface nearly smooth with few tufts of setae; cutting edge with 1 small calcareous tooth at 0.4 length and with row of small corneous teeth in distal 0.6, terminating in small corneous claw. Palm shorter than carpus; dorsolateral margin with crenulate ridge extending nearly to tip of fixed finger, dorsomesial margin not delimited; convex dorsal surface covered with coarse granules; lateral face with scattered low, occasionally squamiform granules; mesial face with coarse granules. Cutting edge of fixed finger with row of small calcareous teeth in proximal 0.6 and with row of small corneous teeth in distal 0.4, terminating in small corneous claw. Carpus subequal in length to merus and about 1.4 times longer than distal width; dorsolateral and dorsomesial margin not delimited; surfaces with coarse granules, dorsomesial surface occasionally with irregular row of small spines; lateral ridge absent. Merus with several low, transverse ridges on dorsal surface; lateral face nearly smooth, ventrolateral margin with subdistal 2 or 3 small spines followed by row of small tubercles; mesial face smooth, ventromesial margin unarmed. Ischium unarmed.

Left cheliped ( Fig. 38E–G ) moderately long and slender, similar between males and females. Chela 2.5–2.6 times longer than broad. Dactylus longer than palm, with sparse tufts of setae on surfaces (setae on ventral surface longest); dorsal surface unarmed, but with faint median ridge proximally; cutting edge with fine row of small corneous teeth, terminating in small corneous claw. Palm about half length of carpus; dorsal surface slightly elevated in mid­line and bearing scattered tiny tubercles, dorsolateral and dorsomesial margins not delimited; lateral, mesial and ventral surfaces nearly smooth, with few short setae dorsally and with scattered long setae on ventral surface. Cutting edge of fixed finger with short row of small calcareous teeth at midlength and row of small corneous teeth in distal part, terminating in small corneous claw. Carpus moderately slender, somewhat compressed laterally, 0.8–0.9 length of chela and shorter than merus; length 2.7–2.8 of distal width and 2.0–2.2 of greatest height; dorsolateral margin not delimited, dorsomesial margin with row of moderately large spines; surfaces faintly granular, lateral face nearly perpendicular, devoid of median ridge; ventrolateral distal margin with 2 or 3 small spines; scattered long setae on mesial and ventral surfaces. Merus with 1 faint transverse ridge on dorsal surface subdistally, dorsodistal margin unarmed; lateral face faintly granular, ventrolateral margin with row of moderately large spines; mesial face smooth, but with some long setae ventrally, ventromesial margin faintly tuberculate; ventral surface weakly concave, with few small, low tubercles and long stiff setae. Ischium with row of tiny denticles on ventromesial margin, other surfaces unarmed.

Ambulatory legs ( Fig. 39A, B ) relatively short and stout, similar from right to left. Dactyli ( Fig. 39C, D ) 0.5–0.7 length of propodi, 3.9–4.1 times longer than high, terminating in large corneous claws; dorsal surfaces each with sparse short setae; lateral and mesial faces each with few tufts of short setae, mesial faces unarmed; ventral margins each with 4–6 long corneous spines notably increasing in size distally. Propodi slightly tapering distally, 3.9–4.4 times longer than high; dorsal surfaces each with row of low protuberances and short stiff setae; lateral faces smooth or faintly punctate; ventral margins each with row of 1–3 small corneous spinules, ventrodistal margins each with paired corneous spines. Carpi each with small dorsodistal spine, dorsal surface smooth, but with row of sparse short setae; lateral faces nearly smooth. Meri each with row of low protuberances (second) or smooth (third), and with tufts moderately short setae; lateral surfaces nearly smooth; ventrolateral distal margins each with small subdistal spine (second) or unarmed (third), ventral surfaces each with row of very small tubercles (second) or smooth (third), all with sparse short to moderately long setae.

Fourth pereopods ( Fig. 36D–F ) similar from right to left both in male and female. Dactyli moderately broad, terminating in small corneous claws; dorsal margins each with row of moderately long setae. Propodi with nearly flat mesial faces bearing row of tufts of short setae ventrally. Carpi moderately setose.

Anterior lobe of sixth thoracic sternite ( Fig. 36G ) subrectangular, slightly widened anteriorly; anterolateral angles rounded, anterior margin with row of moderately short setae. Eighth thoracic sternite ( Fig. 36H ) composed of two subequal, narrowly separated, rounded lobes.

Males with coxae of fifth pereopods markedly unequal ( Fig. 36H ). Right with clearly demarcated, prominent ventromesial protrusion; setae composing tuft arising submarginally from ventromesial protrusion, directed toward midline and passing across left coxa; papilla­like right sexual tube apparent, but masked by tuft of setae; left coxa with gonopore partially masked by tuft of setae directed ventrally. Females with unpaired left gonopore.

Telson ( Fig. 36I ) with terminal margins oblique, bearing 3–5 spinules.

Colour in life. ( Fig. 46A ) Shield generally white or pale gray, with pair of dark brown blotches proximal to base of ocular peduncles. Ocular peduncles generally white, each with small brown spot at base of cornea and on mesial face centrally. Antennular peduncles with ultimate segment banded with dark brown and white (dark brown band occupying distal two­thirds; penultimate segment largely dark brown, distal and proximal parts white; basal segment with dark brown blotch on mesial face, otherwise white. Antennal peduncle with fifth segment having dark brown stripe on lateral and mesial faces; fourth segment dark brown in distal half, white in proximal half; third and second segments white in distal one­third, remainder dark brown; flagellum banded with brown and white. Third maxilliped banded with dark brown and white (dactylus white, propodus largely dark brown, carpus medially dark brown band, otherwise white, merus white in distal one­third, otherwise dark brown. Chelipeds and ambulatory legs also banded. Chelae with fingers white, palms dark brown; carpi mostly dark brown, distal parts with white markings; meri each with dark brown band medially, distal and proximal parts white; ischia mostly brown. Ambulatory dactyli each with dark brown band in proximal 0.2–0.3; propodi each with broad median band, distal 0.4 and proximal 0.2 white; carpi white in distal 0.2–0.3, remainder dark brown; meri each with brown band medially, otherwise white; ischia entirely white.

Distribution

Known only from the Ryukyu and Izu Islands and Kochi Prefecture, Japan ( Fig. 48 ); intertidal to 2 m.

Remarks

Pagurixus pseliophorus closely resembles P. brachydactylus n. sp. in the short and stout ambulatory dactyli. Morphological differences between the two species are summarized in Table 2, and discussed under the account of P. brachydactylus n. sp.

Etymology

From the Greek pseliophoros, carrying a bracelet, in reference to the brown bands on the ambulatory legs.

Figures

FIGURE 36. Pagurixus pseliophorus n. sp. Holotype male (SL 2.8 mm) from Kume­jima Island (CBM­ZC 7856). A, shield and cephalic appendages, dorsal view; B, left antennule, lateral view; C, ultimate segment of left antennular peduncle, ventral view; D, left fourth pereopod, dactylus and propodus, lateral view; E, same, mesial view; F, right fourth pereopod, dactylus and propodus, lateral view; G, sixth thoracic sternite, ventral view; H, coxae of fifth pereopods and eighth thoracic sternite, ventral view; I, telson, dorsal view. Scale bars: 1 mm for A; 0.5 mm for B–I.

FIGURE 37. Pagurixus pseliophorus n. sp. Holotype male (SL 2.8 mm) from Kume­jima Island (CBM­ZC 7856). Right cheliped. A, chela, dorsal view; B, entire right cheliped, mesial view; C, same, lateral view; D, carpus, dorsal view. Scale bar: 1 mm.

FIGURE 38. Pagurixus pseliophorus n. sp. A–C, paratype ovigerous female (SL 2.2 mm) from Kume­jima Island (CBM­ZC 7857); D, paratype female (SL 4.2 mm) from Hane­misaki, Kochi Prefecture; E–G, holotype male (SL 2.8 mm) from Kume­jima Island (CBM­ZC 7856). A, right cheliped, chela and carpus, dorsal view; B, entire right cheliped, mesial view; C, same, lateral view; D, carpus of right cheliped, mesial view; E, left cheliped, chela and carpus, dorsal view; F, entire left cheliped, mesial view; G, same, lateral view. Scale bars: 0.5 mm.

FIGURE 39. Pagurixus pseliophorus n. sp. Holotype male (SL 2.8 mm) from Kume­jima Island (CBM­ZC 7856). 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. Scale bar: 1 mm for A, B; 0.5 mm for D, E.

FIGURE 40. Pagurixus ruber n. sp. A–C, G–I, holotype male (SL 2.4 mm) from Kume­jima Island (CBM­ZC 7862); D–F, paratype male (SL 2.1 mm) from Guam (UF 7305). A, shield and cephalic appendages, dorsal view; B, left antennule, lateral view; C, ultimate segment of left antennular peduncle, ventral view; D, left fourth pereopod, dactylus and propodus, lateral view; E, same, mesial view; F, right fourth pereopod, dactylus and propodus, lateral view; G, sixth thoracic sternite, ventral view; H, coxae of fifth pereopods and eighth thoracic sternite, ventral view; I, telson, dorsal view. Scale bars: 1 mm for A; 0.5 mm for B–I.

FIGURE 46. A, Pagurixus pseliophorus n. sp., paratype male (SL 3.3 mm) from Saga, Kochi Prefecture, Japan (CBM­ZC 8533), photo taken by T. Komai; B, Pagurixus ruber n. sp., paratype male (SL 2.3 mm) from Izu­oshima Island, Izu Islands, Japan (CMNH­ZC 1873), photo taken by J. Okuno.

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. ().