Pseudopaguristes araeos, Rahayu, 2007

Rahayu, Dwi Listyo, 2007, The hermit crabs Paguristes Dana, 1851 s. l. (Crustacea, Decapoda, Anomura, Diogenidae) from the western Indian Ocean, Zoosystema 29 (3), pp. 515-534 : 526-528

Pseudopaguristes araeos n. sp.

( Fig. 4 )

TYPE MATERIAL. — Madagascar. 15°20.0’S, 46°11.8’E, 245- 250 m, 7.XI.1972, holotype, ♂ (3.4 mm) (left 2nd pereopod missing) (MNHN-Pg 7742). — 15°21.0’S, 46°12.5’E, 150 m, 8.XI.1972, paratype, ♂ (4.7 mm) (MNHN-Pg 7743).

ETYMOLOGY. — From the Greek araios, meaning thin or narrow, in reference to the ocular peduncles, which are narrowed distally.

TYPE LOCALITY. — Madagascar.

DISTRIBUTION. — Madagascar; 150 to 250 m.

DESCRIPTION

Eight pairs of biserial gills; branchiostegites each with one or two spinules distally on distal and dorsal margins, concealed by moderately dense setae. Shield ( Fig. 4A ) slightly longer than broad; dorsal surface with few tubercles or subacute spines and several tufts of setae laterally, few scattered tufts dorsolaterally. Rostrum low and broad, not reaching bases of ocular acicles and considerably shorter than lateral projections. Lateral projections obtusely triangular, without terminal spine.

Ocular peduncles subequal, left slightly longer than right, 0.8 of shield length, slender, swollen basally, tapering distally; dorsomesial faces of peduncles each with row of moderately dense and long setae; corneal diameter 0.1 peduncular length. Ocular acicles subtriangular, terminating subacutely or in simple terminal spine; separated by less than basal width of one acicle. Interocular lobe subquadrate, with several spinules distally.

Antennular peduncles, when fully extended, exceeding left cornea by 0.75 length of ultimate segment; basal segment with small distal spine on lateral face of statocyst lobe.

Antennal peduncles reaching 0.8 of left ocular peduncle; fifth segment with few scattered setae; fourth and third segments each with ventrodistal margin drawn out into acute spine; second segment with dorsolateral distal angle produced, terminating in simple or bifid spine, lateral and ventral surfaces with sparse long setae, dorsomesial distal angle with small spine, mesial margin with dense setae; first segment unarmed. Antennal acicle reaching to proximal 0.3 of fifth peduncular segment, terminating in prominent bifid spine; one spine on lateral margin and moderately dense and long setae concealing armature. Antennal flagellum slightly longer than shield; articles each with two to four moderately long setae proximally, slightly more numerous and longer setae distally.

Chelipeds subequal, armature similar; left slightly larger. Left cheliped ( Fig. 4B ) with dactyl almost twice length of palm; dorsomesial margin delimited by row of large tubercles, larger spines proximally becoming smaller distally, dorsal surface with irregular rows of tubercles, accompanied by long sparse setae; mesial face ( Fig. 4C ) with two irregular rows of tubercles: one in midline and one near dorsal margin, several tubercles and protuberances near ventral margin, obscured by covering of moderately long, dense setae; cutting edge with row of large calcareous teeth, one larger tooth medially, terminating in small corneous claw; moderately wide hiatus between dactyl and fixed finger. Palm with row of moderately large spines on dorsomesial margin, convex dorsal surface with rows of tuberculate spines, each accompanied by long sparse setae, dorsolateral margin with row of tuberculate spines, becoming more prominent distally on fixed finger and concealed by moderately dense long setae; mesial face with scattered spinulose tubercles; ventral margin with prominent tuberculate spines; lateral face of palm and fixed finger with irregular rows of spinulose tubercles, ventral surface with irregular rows of spinulose tubercles, increasing in size on fixed finger and accompanied by tufts of setae; cutting edge of fixed finger with row large calcareous teeth, one larger tooth medially, terminating in small corneous claw. Carpus with row of moderately prominent spines on dorsomesial margin; dorsolateral margin not delimited, dorsal and lateral surfaces with numerous, small tuberculate spines, each accompanied by long setae; mesial face with row of small spinulose tubercles on distal margin, partially obscured by tufts of long setae, remainder of surface with low, spinulose tubercles, accompanied by tufts of setae. Merus with row of spines on distal margin extending onto lateral and mesial faces, dorsal surface with subdistal short, transverse row of spines also extending onto lateral and mesial faces, remainder of dorsal margin with row of spinules; mesial face smooth, ventromesial margin with double row of small, spinulose tubercles or tuberculate spines and tufts of dense setae; lateral face spinulose, at least ventrally, ventrolateral margin with row of small, tuberculate spines and long setae; ventral surface with covering of short, dense setae. Ischium with row of small tubercles on ventromesial margin concealed by long dense setae.

Right cheliped with same armature as left but with more prominent spines and tubercles.

Second and third pereopods ( Fig. 4D, E ) differ somewhat in armature; right pereopods slightly longer than left. Dactyls 1.6 longer than propodi; dorsal margins each with moderately stiff, long setae; ventral margins each with one or two tiny spines and long setae; lateral faces each with row of sparse tufts of short setae medially; mesial face of right second with three rows of tufts of long setae, medial row with longer setae, mesial faces of third each with three irregular rows of sparse tufts of moderately long setae. Propodus of right second pereopod with row of prominent spines on dorsal surface accompanied by tufts of long setae; propodi of third pereopods unarmed, dorsal surfaces each with sparse tufts of setae; ventral margins of second and third pereopods each with sparse tufts of setae; mesial faces each with three rows of sparse tufts of long setae; lateral faces each with two rows of sparse tufts of setae. Carpi each with shallow longitudinal sulcus on lateral face accompanied by scattered long and moderately dense setae; carpus of right second pereopod with dorsal row of prominent spines and few small spines and tuft of moderately long setae; carpi of third pereopods each with prominent dorsodistal spine and tufts of setae. Merus of right second pereopod with few spinules on ventral margin and dorsal margin with rows of long setae, third unarmed, but with long setae. Ischia unarmed but with dense ventral setae. Fourth pereopods ( Fig. 4F ) each with small preungual at base of claw; no dorsodistal spine on carpus.

Male first pleopods ( Fig. 4G. H ) each with tuft of setae on superior mesial angle of basal lobe; single row of small hook-like corneous spines on distal margin of inferior lamella; external lobe overreaching inferior lamella, internal lobe broad, with marginal setae and moderately dense setae covering inner surface. Second pleopods ( Fig. 4I, J ) each with basal segment and endopod glabrous; appendix masculina broad, fan-shaped, with long setae on distal margin and inferior surface. Left pleopods 3-5 with well developed exopods; endopods very rudimentary. Female unknown.

Telson ( Fig. 4K ) with deep lateral incisions; median cleft small, shallow; posterior lobes markedly asymmetrical, terminal margins armed with four spines on each lobe.

VARIATION

The chelipeds of the paratype, which are larger than those of the holotype, have larger and denser tubercles and tuberculate spines on the dorsal surfaces of the dactyls and fixed fingers. The dactyls of the second and third pereopods are slightly curved, and 1.5 the length of the propodi. The second left pereopod have the same armament as the right. The telson has five and three spines on the left and right lobes, respectively.

REMARKS

Pseudopaguristes araeos n. sp. is similar to P. laurentae in the shape of the antennal acicles which are triangular, and the ocular peduncles swollen basally. However, in the new species the ocular peduncles are much slenderer with small, elongate corneas compared to the stout ocular peduncles and small rounded corneas in P. laurentae . The appendix masculina of the second male pleopods of P. laurentae is not as broad as in P. araeos n. sp. Other characters that distinguish this new species from P. laurentae are the presence of three irregular rows of tuberculate spines on the mesial face of the dactyl of the cheliped ( P. laurentae has only one row of spines on the mesial face of this appendage), the presence of only one or two tiny corneous spines on ventral margin of each dactyl of the second and third pereopods ( P. laurentae has a row of few spines distally), and the presence of a preungual process on the base of dactylar claw of the fourth pereopod (in P. laurentae the preungual process is absent).

Figures

FIG. 4. — Paguristes araeos n. sp., holotype, ♂, 3.4 mm: A, shield and cephalic appendages; B, left cheliped, dorsal view; C, dactyl of left cheliped, mesial face; D, left second pereopod, lateral view; E, right third pereopod, lateral view; F, left fourth pereopod, lateral view; G, male first pleopod, external view; H, same, internal view; I, male second pleopod, internal view; J, same, external view; K, telson, dorsal view. Setae partially omitted. Scale bars: 1 mm.