Pagurixus pilosus, 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 : 1314-1320

Pagurixus pilosus sp. nov.

( Figures 20–22 )

Material examined

Holotype. RAPA, stn 4, Rarapai Island , Rapa Islands, Austral Islands, French Polynesia, 27°34.3’S, 144°22.1’W, 18 m, 4 November 2002, male SL 2.9 mm (MNHN-Pg 8321).

Paratypes. French Polynesia, Austral Islands. RAPA, stn 30, Point Mei , 27°38.2′S, 144°18.2′W, 16–20 m, dead coral, 18 November 2002, 1 female SL 2.8 mm (MNHN- Pg 8322). BENTHAUS, stn DW 1917, Nelson Reef, 27°03.3′S, 146°03.8′W, 50–60 m, 11 November 2002, 1 male SL 2.5 mm (MNHN-Na 8323) .

Description

Shield ( Figure 20A ) about 1.3 times longer than wide; anterior margin between rostrum and lateral projections slightly concave; anterolateral margins sloping; dorsal surface convex, with few tufts of setae laterally. Rostrum narrowly triangular, not reaching level of midlength of ocular acicles, terminating in acute spine. Lateral projections obtusely triangular, each with small submarginal spine.

Ocular peduncles ( Figure 20A ) relatively slender, about 0.7 length of shield, each with row of tufts of setae on dorsal surface mesially (setae at base of cornea not reaching distal corneal margin); corneas 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 20A ) overreaching distal corneal margins by about 0.2–0.3 lengths of ultimate segments. Ultimate segment with tufts of long setae at dorsolateral distal angle; ventral surface with two longitudinal rows of tufts of short setae directed outward ( Figure 19B ). Basal segment with small laterodistal spine on statocyst lobe. Ventral flagellum with thick long setae on lateral and mesial margins.

Antennal peduncles ( Figure 20A ) overreaching distal corneal margins by 0.2–0.3 lengths of fifth segments. Third segment with small spine at ventromesial distal angle, practically obscured by tuft of stiff setae. Second segment with spinule at dorsodistal mesial angle; laterodistal projection falling far short of midlength of fourth segment, terminating in simple or bifid spine. First segment unarmed on lateral surface; ventromesial distal margin with flattened rounded projection, bearing few spinules anterolaterally. 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 5.0 length of shield; each article with few very short setae distally.

Male right cheliped ( Figure 21A–C ) not particularly elongate, moderately stout, distinctly longer than left cheliped. Chela subovate in dorsal view, about 1.8 times than broad. Dactylus distinctly shorter than palm, noticeably curved ventrally, terminating in calcareous claw; dorsomesial margin not delimited; surfaces minutely granular; cutting edge with one obtuse calcareous tooth proximal to midlength. Palm longer than carpus; convex dorsal surface minutely granular, without conspicuous spines; dorsolateral and dorsomesial margins not delimited; lateral, mesial and ventral surfaces minutely granular. Fixed finger terminating in calcareous claw; cutting edge with one obtuse calcareous tooth at about midlength. Carpus about 1.4 times longer than broad; dorsal surface minutely granular, with double row of sharp spines mesially in proximal 0.7; dorsolateral and dorsomesial margins not delimited; sloping lateral surface without longitudinal median ridge, ventrolateral margin convex, smooth; mesial face with scattered tufts of moderately long setae, ventromesial margin smooth; ventral surface convex, nearly smooth. Meral–carpal articulation lacking any pronounced clockwise rotation; dorsal surface of merus with short transverse ridges or low protuberances and short stiff setae, nearly smooth, dorsodistal margin with one small spine and with row of stiff setae; lateral face nearly smooth, ventrolateral margin with three moderately small spines distally; mesial face also smooth, with long setae, ventromesial margin with row of small spines or tubercles in distal half; ventral surface convex, with several long setae mesially. Ischium with smooth ventromesial margin; surfaces unarmed.

Female right cheliped ( Figure 22A–D ) somewhat larger than left. Chela narrowly subtriangular, about 2.4 times longer than broad. Dactylus very slightly curved ventrally, longer than palm; dorsomesial margin delimited by row of small tubercles; dorsal surface with row of small tubercles extending nearly to tip along midline; mesial face with scattered small tubercles or coarse granules; ventral surface with few tufts of stiff setae; cutting edge with row of small, blunt or subacute calcareous teeth in proximal half and with row of small corneous teeth in distal half, terminating in small corneous claw. Palm about 0.7 length of carpus; dorsal surface slightly convex, with scattered small, spinulose tubercles, median row of small spines extending onto fixed finger, and mesial row of larger spines; lateral margin delimited by row of small spines or spiniform tubercles extending nearly to tip of fixed finger; dorsomesial margin weakly delimited by row of small spines; lateral face coarsely granular; mesial face with scattered small tubercles; ventral surface weakly convex, with small, low protuberances and tufts of stiff setae. Fixed finger terminating in small corneous claw, with row of small, subacute calcareous teeth in proximal 0.8 and row of small corneous teeth in distal 0.2. Carpus about 2.0 times longer than wide, subequal in length to chela or merus; dorsal surface with mesial row of moderately small spines and scattered small spines or spinulose tubercles, dorsomesial margin with row of small to moderately small spines and tufts of long setae, dorsolateral margin not delimited; sloping lateral face coarsely granular, devoid of longitudinal ridge, ventrolateral margin weakly tuberculate in distal 0.3; mesial surface also coarsely granular, with tufts of stiff setae dorsally, ventromesial margin tuberculate; ventral surface moderately convex, nearly naked. Merus with low transverse ridges in distal half, dorsodistal margin with one prominent spine and several stiff setae; lateral face nearly smooth, ventrolateral margin with three moderately small subdistal spines followed by row of tiny tubercles; mesial face nearly smooth, ventromesial margin with one distal spine and row of small tubercles. Ischium with smooth ventromesial margin; surfaces unarmed.

Left cheliped ( Figure 21D–G ) similar between male and female, relatively slender. Chela elongate, about 3.2 times longer than broad. Dactylus longer than palm, with sparse tufts of setae on surfaces; cutting edge with row of small corneous teeth over entire length, terminating in small corneous claw. Palm about half length of carpus; dorsal surface weakly convex, with mesial row of small tubercles and with row of minute tubercles on slightly elevated midline extending onto base of fixed finger; dorsolateral and dorsomesial margins not delimited; lateral face with scattered very low, subsquamiform protuberances; mesial face with small tubercles dorsally and otherwise smooth, with some 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, subacute calcareous teeth interspersed with minute corneous teeth. Carpus relatively slender, somewhat compressed laterally, subequal in length to chela or merus; length about 3.1 of distal width and about 2.5 of greatest height; dorsolateral margin with one distal spine followed by row of minute tubercles, dorsomesial margin with row of small spines in distal 0.6, dorsodistal margin with one small spine medially; tufts of long setae on both dorsolateral and dorsomesial margins; lateral face nearly perpendicular, with low granules, devoid of median ridge, ventrolateral margin unarmed, with sparse long setae; mesial face nearly smooth, with tufts of long setae dorsally and ventrally, ventromesial margin unarmed. Merus with few low transverse ridges on dorsal surface distally, dorsodistal margin with long stiff setae; lateral face nearly smooth, ventrolateral margin with three moderately small spines in distal half; mesial surface nearly smooth, with tufts of short to long setae dorsally and ventrally, ventromesial margin weakly tuberculate; ventral surface weakly convex, with several long stiff setae. Ischium with small spine on laterodistal margin; ventromesial margin smooth.

Ambulatory legs ( Figure 20C, E ) relatively long and slender, similar in general structure from right to left, but left third with denser setation. Dactyli ( Figure 20D, F, G ) 0.9–1.0 length of propodi, 5.8–6.7 times longer than broad, slightly curved ventrally, terminating in strong corneous claws; dorsal surfaces with sparse setae; lateral surfaces with sparse short setae dorsally and ventrally (second and right third), or with scattered tufts of long setae directed outward (left third); mesial faces unarmed (second) or with few corneous spinules dorsally (third); ventral margins each with 8–10 corneous spines notably increasing in size distally. Propodi slightly tapering distally, 3.8–4.2 times longer than broad; dorsal surfaces nearly smooth, with moderately short stiff setae; lateral surfaces nearly smooth, with few short setae on second and right third, with scattered tufts of moderately long setae in distal half on left third; ventral margins each with row of one to three corneous spinules distally, ventrodistal margins each with paired small corneous spines. Carpi usually with small dorsodistal spines; dorsal surfaces nearly smooth, with moderately long stiff setae. Meri each with sparse row of tufts of stiff setae on nearly smooth dorsal surface; lateral surfaces nearly smooth; ventrolateral distal margins each with small subdistal spine (second) or unarmed (third), ventral margins slightly convex, naked or with few setae.

Left fourth pereopod of male ( Figure 20H ) with prominent tuft of stiff setae on dactylus; dactylus moderately broad, terminating in minute corneous claw; propodus with tuft of setae on dorsal surface, mesial face nearly flat, propodal rasp of single row of corneous scales; carpus also with numerous setae on dorsal surface. Right fourth pereopods of males not preserved. In female, fourth pereopods subequal and similar, without prominent tufts of setae on dactyli and propodi.

Anterior lobe of sixth thoracic sternite ( Figure 20I ) subrectangular, anterolateral angles rounded; ventral surface with transverse row of stiff setae anteriorly. Eighth thoracic sternite ( Figure 20J ) composed of two unequal, narrowly separated, rounded lobes.

Coxae of fifth pereopods ( Figure 20J ) markedly unequal in male. Right coxa with prominent posteromesial protrusion, tuft of long stiff setae arising from surface of prominent posteromesial protrusion, directed toward left and reaching to left coxa; no protrusion of vas deferens apparent. Left coxa with small gonopore. Female with paired gonopores.

Telson missing.

Colouration

In preservative. No trace of markings apparent.

Size

Largest male SL 2.9 mm, unique available female SL 2.8 mm.

Distribution

Known only from Austral Islands, French Polynesia, 16–60 m.

Etymology

From the Latin pilosus meaning setose, referring to the characteristic setation of the dactylus and propodus of the left third pereopod.

Remarks

Pagurixus pilosus is placed in the subgroup A of the P. boninensis group (cf. Komai and Osawa 2006) because of the lack of division of the lateral face of the carpus of the left cheliped. It appears closest to P. boninensis . However, the new species is unique within the genus in having scattered prominent tufts of long setae on the lateral faces of the dactylus and propodus of the left third pereopod. Furthermore, P. pilosus differs from P. boninensis in the more slender ocular peduncles and the spinose right chela in female. Unfortunately, the living colouration was not recorded for this new species.

Figures

Figure 19. Pagurixus formosus sp. nov. (A, D–F) Holotype, male (shield length [SL] 2.9 mm; FMNH 5179a); (B–C) paratype, ovigerous female (SL 3.0 mm; FMNH 5179b). (A) Right chela and carpus, dorsal view; (B) right chela, dorsal view; (C) carpus of right cheliped, dorsal view; (D) left chela and carpus, dorsal view; (E) left cheliped, mesial view; (F) left cheliped, lateral view. Notes: Scale bars, (A) 2 mm; (B–F) 1 mm.

Figure 20. Pagurixus pilosus sp. nov. holotype, male (shield length 2.9 mm; MNHN-Pg 8321). (A) Shield and cephalic appendages, dorsal view; (B) ultimate segment of antennular peduncle, ventral view; (C) right second pereopod, lateral view; (D) right second pereopod, dactylus, mesial view; (E) left third pereopod, lateral view; (F) left third pereopod, dactylus, ventral view; (G) left third pereopod, mesial view; (H) distal three segments of left fourth pereopod, lateral view; (I) sixth thoracic sternite, ventral view; (J) coxae of fifth pereopods and eighth thoracic sternite, ventral view. Notes: Scale bars, (A, C, E) 1 mm; (B, D, F–J) 0.5 mm.

Figure 21. Pagurixus pilosus sp. nov. holotype, male (shield length 2.9 mm; MNHN-Pg 8321). (A) Right chela and carpus, dorsal view; (B) right cheliped, mesial view; (C) right cheliped, lateral view; (D) left chela, dorsal view; (E) left cheliped, mesial view; (F) left cheliped, lateral view; (G) carpus of left cheliped, dorsal view. Note: Scale bars, 1 mm.

Figure 22. Pagurixus pilosus sp. nov. paratype, female (shield length 2.8 mm; MNHN-Pg 8322). (A) Right chela, dorsal view; (B) right cheliped, mesial view; (C) right cheliped, lateral view; (D) carpus of right cheliped, dorsal view. Note: Scale bar, 1 mm.