Pagurixus crosnieri, Komai, 2010

Komai, Tomoyuki, 2010, New species and new records of the hermit crab genus Pagurixus Melin, 1939 (Crustacea: Decapoda: Anomura: Paguridae) from the Indo-West Pacific, Journal of Natural History 44 (21 - 22), pp. 1269-1342 : 1300-1306

Pagurixus crosnieri sp. nov.

( Figures 14–16 )

Material examined

Holotype. Stn 19/10, Tulear, Madagascar, 1976, male SL 3.0 mm (MNHN-Pg 8311).

Paratypes. Madagascar. Same data as holotype, 2 males SL 2.2, 2.8 mm, 1 female SL 2.2 mm (MNHN-Pg 8312); stn 10/1, Tulear, 1976, coll. P. Galenon, 1 male SL 2.2 mm (MNHN-Pg 8313); stn 18/05, Tulear, 1976, coll. P. Galenon, 1 male SL 2.3 mm (MNHN-Pg 8314) .

Non-type. Stn 35/0.06, Tulear, 1976, coll. P. Galenon, 1 male SL 1.7 mm (MNHN-Pg 8315). Tulear, coll. B. Thomassin, 1 male, 1 ovigerous female (not measured because of poor condition) (MNHN-Pg 3406).

Description

Shield ( Figure 14A ) almost as long as broad; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; dorsal surface slightly convex, with few tufts of setae laterally; lateral margins strongly convex. Rostrum triangular, rather weakly produced, overreaching lateral projections, terminating acutely. Lateral projections triangular, each with small submarginal spine.

Ocular peduncles ( Figure 14A ) relatively slender, 0.6–0.7 length of shield, each with row of tufts of setae on dorsal surface mesially (setae at base of cornea extending beyond distal corneal margin); corneas slightly dilated, corneal width 0.2–0.3 of peduncular length; basal part somewhat inflated, broader than corneal width. Ocular acicles subtriangular, each with small submarginal spine.

Antennular peduncles ( Figure 14A, B ) overreaching distal corneal margins by 0.3–0.5 length of ultimate segment. Ultimate segment with tufts of long setae on dorsolateral distal portion; ventral surface with two longitudinal rows of tufts of short setae (setae directed outward) ( Figure 14C ). Basal segment with small laterodistal spine on statocyst lobe. Ventral flagellum ( Figure 14B ) with dense long setae on lateral and mesial margins.

Antennal peduncles ( Figure 14A ) overreaching distal corneal margins by about 0.2 length of fifth segment. Third segment with small spine at ventromesial distal angle, practically obscured by tuft of stiff setae. Second segment unarmed at dorsomesial distal angle; laterodistal projection reaching nearly to midlength of fourth segment, terminating in simple or bifid spine. First segment unarmed; ventromesial distal margin with flattened blunt projection. Antennal acicle moderately long, arcuate, overreaching base of cornea but not reaching distal corneal margin; mesial margin with row of tufts of stiff setae. Flagellum moderately long, exceeding 4.0 length of shield; each article with short setae distally.

Male right cheliped ( Figure 15A–C ) not particularly elongate, moderately stout, distinctly longer than left cheliped. Chela subovate in dorsal view, 1.6–1.7 times longer than broad. Dactylus distinctly shorter than palm, terminating in calcareous claw; dorsomesial margin not delimited; surfaces granular; cutting edge with one small blunt calcareous tooth proximally. Palm longer than carpus; convex dorsal surface granular, without conspicuous spine; dorsolateral and dorsomesial margins not delimited; lateral, mesial and ventral surfaces granular. Fixed finger terminating in calcareous claw; cutting edge with two obtuse teeth. Carpus about 1.2 times longer than broad; dorsal surface granular, without conspicuous spines; dorsolateral and dorsomesial margins not delimited; sloping lateral surface without longitudinal median ridge, ventrolateral margin sinuous, smooth; mesial face nearly naked, ventromesial margin granular; ventral surface convex. Meral–carpal articulation lacking any pronounced clockwise rotation; dorsal surface of merus nearly smooth, dorsodistal margin with row of stiff setae; lateral face nearly smooth, ventrolateral margin with one or two moderately small spines distally followed by row of granules; mesial face also smooth, with long setae along ventral margin, ventromesial margin unarmed; ventral surface slightly convex, with several long setae. Ischium with smooth ventromesial margin; surfaces unarmed.

Right cheliped missing in all female specimens examined.

Left cheliped ( Figure 15D–F ) similar between male and female, moderately slen- der. Chela 2.6–2.7 times longer than broad. Dactylus slightly longer than palm, with sparse setae on surfaces; cutting edge with row of small corneous teeth, terminating in small corneous claw. Palm about half length of carpus; dorsal surface weakly convex, sparsely granular, with row of small spinulose tubercles adjacent to dorsomesial margin; dorsolateral margin not delimited, dorsomesial margin delimited by row of small spines; lateral face with sparse granules often forming short oblique rows; mesial face smooth, with few tufts of moderately long setae; ventral surface slightly convex, with small low protuberances laterally. Fixed finger terminating in small corneous claw; cutting edge with row of small corneous teeth in distal half. Carpus relatively slender, subequal in length to chela or merus; length about 2.4 of distal width and about 2.4 of greatest height; dorsolateral margin with row of tiny tubercles, dorsomesial margin with row of five or six small spines, dorsodistal margin with one small spine medially; lateral face steeply sloping, coarsely granular, without longitudinal median ridge, ventrolateral margin unarmed; mesial face with few spinulose tubercles dorsally and with several tufts of short to long stiff setae directed mesially, ventromesial margin unarmed. Merus smooth on dorsal surface, dorsodistal margin with stiff setae; lateral face nearly smooth, ventrolateral margin with one or two spines distally; mesial surface nearly smooth, with short row or tufts of long stiff setae ventrally, ventromesial margin unarmed; ventral surface weakly convex, with several long stiff setae. Ischium unarmed.

Ambulatory legs ( Figure 16A, C ) moderately long and stout, generally similar from right to left. Dactyli ( Figure 16B, D ) 0.9–1.1 length of propodi, 5.3–5.5 times longer than wide, terminating in large corneous claws; dorsal surfaces each with few short setae; lateral and mesial faces each with some individual or tufts of short setae, mesial faces unarmed; ventral margins each with seven or eight relatively long corneous spines notably increasing in size distally. Propodi slightly tapering distally, 3.2–3.8 times longer than wide; dorsal surfaces nearly smooth, bearing tufts of short to moderately long stiff setae; lateral faces nearly smooth, with few short setae; ventral margins each with row of four to six corneous spinules, ventrodistal margins each with paired corneous spines. Carpi each with small dorsodistal spine, dorsal surfaces otherwise unarmed, with sparse setae; lateral faces smooth. Meri nearly smooth on dorsal surfaces, each with single seta or sparse tufts of setae; lateral surfaces smooth; ventrolateral distal margins each with small subdistal spine (second) or unarmed (third); ventral surfaces smooth, with few setae.

Fourth pereopods ( Figure 14D, E ) dissimilar. Dactyli terminating in very small corneous claws, with numerous, dense long setae on dorsal margins (setae much longer and more numerous on left than on right); left dactylus much broader than right. Propodi each with tuft of several setae on mesial face at base of ventrodistal extremity; dorsal margin with several long setae on left, much shorter setae on right; each propodal rasp consisting of single row of corneous scales (on left, proximal scales occasionally forming double row); mesial faces nearly flat, with several long setae dorsally. Carpi each with tuft of setae on mesial face near ventrodistal angle and row of setae on dorsal margin (setae longer and more numerous on left than on right).

Anterior lobe of sixth thoracic sternite ( Figure 14F ) roundly subrectangular, anterior margin with numerous stiff setae. Eighth thoracic sternite ( Figure 14G ) composed of two subequal, rather widely separated, rounded lobes, each with short stiff setae anteriorly.

Coxae of fifth pereopods unequal in males ( Figure 14G ). Posteromesial protrusion of right coxa prominent; setae arising from base of posteromesial protrusion, not reaching to left coxa; left coxa lacking gonopore. Female with single left gonopore.

Telson ( Figure 14H ) with terminal margins nearly horizontal, each bearing 10–13 small, unequal spines or spinules; dorsal surfaces adjacent to terminal margins slightly elevated, well calcified.

Colouration

Living colouration unknown. In preservative, faded to straw colour.

Size

Largest male SL 3.0 mm.

Distribution

Known only from Tulear, Madagascar.

Etymology

This new species is dedicated to Alain Crosnier in recognition of his great contributions to carcinology, and for enabling me to study the large fascinating collections of decapods made by various French expeditions.

Remarks

Pagurixus crosnieri sp. nov. falls into the subgroup B of the P. boninensis group (cf. Komai and Osawa 2006) because of the lack of a division of the lateral face of the carpus of the left cheliped. It appears closest to P. ruber . Shared characters of the two species include: the ultimate segment of the antennular peduncle bears setal rows consisting of tufts of short setae; the carpus of the male right cheliped is devoid of conspicuous spines dorsally; the fourth pereopods are unequal and dissimilar, having a prominent tuft of long setae on the left dactylus; and the male right gonopore is absent. The new species, however, can be distinguished from P. ruber by the presence of mesial spines on the left chela and the presence of conspicuous spines on the carpus of the left cheliped. In P. ruber , the left chela is unarmed dorsomesially; there are no conspicuous spines on the dorsal surface of the carpus of the left cheliped. In addition, the lateral margins of the shield are much more strongly convex in P. crosnieri than in P. ruber ; the ocular peduncles are slenderer in P. crosnieri than in P. ruber ; and the posteromesial protrusion on the coxa of the right cheliped is weakly developed in P. crosnieri , but is completely absent in P. ruber . Pagurixus boninensis and P. purpureus Komai and Okuno, 2009 are also similar to P. crosnieri and P. ruber , but the presence of dorsomesial spines on the carpus of the right cheliped and the possession of male left gonopore distinguishes the former two species from the latter two species.

Figures

Figure 14. Pagurixus crosnieri sp. nov. holotype, male (shield length 3.0 mm; MNHN-Pg 8311). (A) Shield and cephalic appendages, dorsal view; (B) left antennule, lateral view; (C) left antennule, ultimate segment, ventral view; (D) distal three segments of left fourth pereopod, lateral view; (E) distal three segments of right fourth pereopod, lateral view; (F) sixth thoracic sternite, ventral view; (G) coxae of fifth pereopods and eighth thoracic sternite, ventral view; (H) telson, dorsal view. Notes: Scale bars, (A–G) 1 mm; (H) 0.5 mm.

Figure 15. Pagurixus crosnieri sp. nov. holotype, male (shield length 3.0 mm; MNHN-Pg 8311). (A) Right chela and carpus, dorsal view; (B) right cheliped, mesial view; (C) right cheliped, lateral view; (D) left chela and carpus, dorsal view; (E) left cheliped, mesial view; (F) left cheliped, lateral view. Note: Scale bar, 1 mm.

Figure 16. Pagurixus crosnieri sp. nov. holotype, male (shield length 3.0 mm; MNHN-Pg 8311). (A) Right second pereopod, lateral view; (B) Right second pereopod, dactylus, mesial view; (C) left third pereopod, lateral view; (D) left third pereopod, dactylus, mesial view. Note: Scale bars, 1 mm.