Pagurixus concolor, 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 : 41-48

Pagurixus concolor n. sp.

( Figs. 15–18 , 44D , 47 )

Pagurixus cf. laevimanus . — Paulay et al., 2003: 490.

Type material

HOLOTYPE: CBM­ZC 7860, male (SL 2.5 mm), south reef, Vadoo , Maldives, 10 m, under coral rock, SCUBA, coll. K. Nomura, 19 April 1996.

PARATYPES. Maldives: CBM­ZC 7861, 1 male (SL 2.5 mm), same data as holotype; CBM­ZC 7870, 1 female (SL 1.7 mm), 1 ovigerous female (SL 2.2 mm), Helmut Reef, South Male Atoll , 3 m, coll. K. Nomura, 30 August 2003 . Japan: Ryukyu Islands. CBM­ ZC 8255 , 1 female (CL 2.9 mm), Fuki Beach, Kuroshima Island , Yaeyama Islands , lagoon, 2 m, diving, coll. K. Nomura, 3 September 1998 ; CBM­ZC 8483, 1 male (CL 2.7 mm), Sesoko Islet, Okinawa Island , branches of dead coral, 1–2 m, coll. M. Osawa, 12 December 2001 ; CBM­ZC 8484, 1 female (CL 3.2 mm), Tokashiku Bay, Tokashiki Island, Kerama Islands, under dead coral, 1–2 m, coll. M. Osawa, 27 May 2000. Guam: UF 1401 , 2 males (SL 2.7, 3.1 mm), Double reef, 3–6 m, under rubble, coll. V. Bonito , 7 May 2001 ; UF 7298 , 1 male (SL 2.2 mm), 1 ovigerous female (SL 2.4 mm), south of Haputo , 6–9 m, coll. G. Paulay, 2 August 2000 . Samoa: UF 3268 , 1 male (SL 2.8 mm), Au’asi, Tuituila Island, American Samoa , 14°16.29’S, 170°34.37’W, 1.5–2.1 m, under rubble, coll. V. Bonito , 24 October 2002 .

Description

Shield ( Fig. 15A ) 1.0–1.1 times as long as broad; anterior margin between rostrum and lateral projections weakly concave; anterolateral margins sloping; posterior margin truncate; dorsal surface with few tufts of short setae laterally. Rostrum triangular, reaching or slightly overreaching level of midlength of ocular acicles, terminating acutely. Lateral projections obtusely triangular, slightly produced, with small submarginal spine.

Ocular peduncle ( Fig. 15A ) moderately long and stout, 0.6–0.7 length of shield, each with row of tufts of short setae on dorsal surface; corneas slightly to moderately inflated, corneal width 0.4–0.5 of peduncular length; basal part not inflated, narrower than corneal width. Ocular acicles subovate or subtriangular, with small submarginal spine.

Antennular peduncle ( Fig. 15A, B ) overreaching distal margin of cornea by 0.2–0.5 length of ultimate segment. Ultimate segment with tufts of long setae at dorsolateral and dorsomesial angles; each setal row on ventral surface consisting of long setae directed laterally and shorter setae directed ventrally or proximally ( Fig. 15C ). Basal segment with small lateral spine on statocyst lobe. Ventral flagellum with numerous long setae on lateral and mesial margins.

Antennal peduncle ( Fig. 15A ) overreaching distal margin of cornea by 0.2–0.4 length of fifth segment. Second segment with small spine at dorsomesial distal angle; laterodistal projection not reaching midlength of fourth segment, terminating in simple or bifid spine. First segment with small laterodistal spine; ventromesial distal margin produced, with spinule just lateral to antennal gland opening. Antennal acicles moderately long, slightly arcuate, overreaching at least base of cornea; mesial margin with row of sparse, stiff setae. Antennal flagellum long, exceeding 7.0 length of shield.

Right cheliped of adult males ( Fig. 16A–C ) somewhat elongate. Chela elongate subovate in dorsal view, 1.9–2.5 times longer than broad. Dactylus 0.6–0.7 times length of palm; dorsomesial margin not delimited; surfaces covered with minute granules; cutting edge with subacute calcareous teeth in proximal 0.7 and fused corneous teeth in distal 0.3, terminating in small corneous claw. Palm slightly shorter than carpus; convex dorsal surface minutely granular, dorsolateral margin faintly to distinctly delimited by granular ridge, dorsomesial margin not delimited; lateral, mesial and ventral surfaces minutely granular, with tufts long setae on ventral surface. Cutting edge of fixed finger with 1 or 2 large teeth in proximal half and with row of small calcareous teeth in distal half, terminating in small calcareous claw. Carpus subequal to merus in length; dorsolateral margin not delimited; dorsomesial margin not delimited or weakly delimited by row of small spines and tubercles (proximal spines larger); all surfaces granular, lateral surface without trace of median longitudinal ridge. Meral­carpal articulation lacking any pronounced clockwise rotation; dorsal surface of merus with row of low transverse ridges, dorsodistal margin unarmed; lateral face with scattered minute vertical ridges, ventrolateral margin with 1 or 2 subdistal spines followed by row of low protuberances or tubercles; mesial face also with small, low protuberances, ventromesial margin with row of small spines or tubercles; ventral surface with few small tubercles and several tufts of long setae. Ischium with row of small denticles on ventromesial margin, otherwise unarmed.

Right cheliped of females ( Fig. 17A–C ) comparatively large for genus. Chela subovate in dorsal view, 1.7–2.0 times longer than broad. Dactylus subequal in length to palm; dorsomesial margin not delimited; surfaces granular; cutting edge with 1 or 2 large calcareous teeth in proximal 0.6 and row of small corneous teeth in distal 0.4, terminating in small corneous claw. Palm shorter than carpus (about 0.8 length of carpus); dorsolateral margin distinctly delimited by crenulate or tuberculate ridge, dorsomesial margin not delimited. Cutting edge of fixed finger with 1 prominent calcareous tooth at midlength and row of partially fused small calcareous teeth in distal 0.4, terminating in small corneous claw. Carpus 1.3–1.6 times longer than distal width, subequal to merus in length; dorsolateral margin not delimited or weakly delimited by row of small proximal spines and distal protuberances; dorsomesial margin not faintly delimited; lateral surface with distinct, faintly crenulate or granular ridge on midline, dorsal section oblique, ventral section perpendicular. Merus with dorsal surface nearly smooth, dorsodistal margin unarmed; lateral face with scattered minute vertical ridge or low tubercles, ventrolateral margin with 1 small subdistal spine followed by row of small tubercles; mesial surface nearly smooth, ventromesial margin with row of tiny tubercles.

Left cheliped ( Fig. 16D–F ) moderately slender, not particularly elongate, similar between male and female. Chela 2.6–3.1 times longer than broad. Dactylus longer than palm, with sparse tufts of setae on surfaces (setae on ventral surface longest); dorsal surface unarmed, dorsomesial margin not delimited; cutting edge with small corneous teeth, terminating in small corneous claw. Palm about half length of carpus; dorsal surface weakly elevated in midline and bearing row of tiny tubercles extending onto fixed finger, sloping mesial part unarmed, dorsomesial margin faintly to moderately delimited by row of low protuberances; lateral part of dorsal surface also sloping, dorsolateral margin faintly delimited; lateral, mesial, ventral surfaces nearly smooth, but with scattered low protuberances and tufts of short to long setae. Cutting edge of fixed finger with row of small calcareous teeth interspersed by small corneous teeth. Carpus subcylindrical, 0.8–1.0 of chela length and shorter than merus; length 2.2–2.9 of distal width and 2.4–2.7 of greatest height; surfaces nearly smooth; dorsolateral and dorsomesial margins each with row of low, small tubercles and long stiff setae; lateral surface divided into oblique dorsal and perpendicular ventral sections by weak longitudinal ridge on midline; mesial surface with scattered tufts of long setae; ventral surface with few low protuberances and several tufts of long setae. Merus with row of low transverse ridges on dorsal surface and sparse short setae, dorsodistal margin unarmed; lateral surface with few granules adjacent to ventrolateral margin, otherwise almost smooth, ventrolateral margin with row of low tubercles or protuberances; mesial face nearly smooth, with few setae, ventromesial margin with row of low, small tubercles. Ischium with row of tiny denticles on ventromesial margin, otherwise unarmed.

Ambulatory legs ( Fig. 18A, B ) comparatively long and slender, similar from right to left. Dactyli ( Fig. 18C, D ) 0.8–1.1 length of propodi, 6.8–8.4 times longer than high, terminating in large corneous claws; dorsal surfaces each with row of sparse short setae; lateral and mesial faces each with few tufts of short setae, mesial faces each unarmed (second) or armed with row of corneous spinules adjacent to dorsal margin (third); ventral margins each with 6–9 long corneous spines notably increasing in size distally. Propodi tapering distally, 4.9–5.1 times longer than high; dorsal surfaces with row of very low protuberances and moderately short stiff setae or bristles; lateral faces smooth; ventral margins each with row of 3–5 long corneous spinules, ventrodistal margins each with paired corneous spines. Carpi each with small dorsodistal spine, dorsal surfaces smooth, but with tufts of short stiff setae; lateral faces nearly smooth, with few short setae dorsally. Meri each with row of low protuberances and short stiff setae or bristles on dorsal surfaces; lateral surfaces with few granules and few short setae; ventrolateral distal margins each with small subdistal spine (occasionally unarmed on third), ventral surface with row of tiny tubercles or spinules (second) or nearly smooth (third), and with tufts of short setae.

Fourth pereopods ( Fig. 15D, E ) similar from right to left in both male and female. Dactyli moderately broad, terminating in small corneous claws, with row of moderately long setae on each dorsal margin. Propodi each with flat mesial face bearing few tufts of short setae.

Anterior lobe of sixth thoracic sternite ( Fig. 15F ) transversely oblong, anterolateral angles rounded, anterior margin with row of moderately short setae. Eighth thoracic sternite ( Fig. 15G ) composed of two subequal, closely set, rounded lobes.

Males with coxae of fifth pereopods slightly unequal ( Fig. 15G ). Right coxa with setal tuft directed toward midline and nearly reaching to left coxa; posteromesial protrusion very short, clearly demarcated; papilla­like very short sexual tube apparent. Left coxa also with papilla­like sexual tube partially masked by tuft of setae directed ventrally. Female with paired gonopores.

Telson ( Fig. 15H ) with terminal margins slightly oblique, each with 4–6 small spines.

Colour in life. ( Fig. 44D ) Chelipeds and ambulatory legs entirely orange, olive or brown, without conspicuous markings.

Distribution

Maldives in the Indian Ocean, and Japan, Guam and Samoa in the western Pacific ( Fig. 47 ); coral reef at depths of 1–10 m. This species is widely distributed in the Indo­ West Pacific .

Remarks

Pagurixus concolor n. sp. has a weak longitudinal ridge on the lateral surface of the carpus of the left cheliped, and therefore it is compared with P. laevimanus , P. maorus , P. tweediei and P. nomurai (Table 1). Pagurixus concolor is distinguished from P. laevimanus , P. maorus and P. tweediei by the carpi of the chelipeds lacking conspicuous spines on the dorsal surfaces and the structure of the setal series on the ultimate segment of the antennular peduncles (Table 1). It is readily separated from P. nomurai by the absence of a lateral ridge on the carpus of the male right cheliped, the less slender left cheliped, and the less elongate ambulatory dactyli (Table 1). The coloration in life is also diagnostic. This new species has an orange, olive or brown base color, lacking conspicuous markings on the chelipeds and ambulatory legs.

Examination of the specimens from Guam ( UF 1401, 7298) has revealed that Pagurixus cf. laevimanus listed by Paulay et al. (2003) is actually P. concolor n. sp.

Etymology

From the Latin concolor , meaning same color, alluding to the coloration of the new species in life.

Figures

FIGURE 15. Pagurixus concolor n. sp. Holotype male (SL 2.5 mm) from Vadoo, Maldives (CBM­ ZC 7860). A, shield and cephalic appendages, dorsal view; B, left antennule, lateral view; C, ultimate segment of antennular peduncle, ventral view; D, left fourth pereopod, dactylus and propodus, lateral view; E, right fourth pereopod, dactylus and propodus, lateral view; F, sixth thoracic sternite, ventral view; G, coxae of fifth pereopods and eighth thoracic sternite, ventral view; H, telson, dorsal view. Scale bars: 1 mm for A; 0.5 mm for B–H.

FIGURE 16. Pagurixus concolor n. sp. Holotype male (SL 2.5 mm) from Vadoo, Maldives (CBM­ ZC 7860). 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: 1 mm.

FIGURE 17. Pagurixus concolor n. sp. Paratype ovigerous female (SL 2.2 mm) from Vadoo, Maldives (CBM­ZC 7870). Right cheliped. A, chela and carpus, dorsal view; B, entire right cheliped, mesial view; C, same, lateral view. Scale bar: 1 mm.

FIGURE 18. Pagurixus concolor n. sp. Holotype male (SL 2.5 mm) from Vadoo, Maldives (CBM­ ZC 7860). 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 bars: 1 mm for A, B; 0.5 mm for C, D.

FIGURE 44. A, Pagurixus maorus (Nobili, 1906), male (SL 3.9 mm) from Kume­jima Island, Ryukyu Islands, photo taken by M. Osawa; B, Pagurixus tweediei (Forest, 1956), male (SL 3.9 mm) from Tahiti, Society Islands, French Polynesia (UF 1731), photo taken by G. Paulay; C, Pagurixus nomurai Komai & Asakura, 1995, ovigerous female from Guam, Mariana Islands (UF), photo taken by G. Paulay; D, Pagurixus concolor n. sp., paratype female (SL 3.2 mm) from Tokashiki Island, Kerama Islands (CBM­ZC 8484), photo taken by M. Osawa.

FIGURE 47. Geographic distribution of Pagurixus laevimanus (), P. maorus (), P. tweediei (), P.nomurai (), P. pulcher () and P. concolor n. sp. ().