Pseudopaguristes gracilis, Rahayu, Dwi Listyo, 2005

Rahayu, Dwi Listyo, 2005, Additions to the Indonesian fauna of the hermit crab genus Pseudopaguristes McLaughlin and a further division of the genus Paguristes Dana (Crustacea: Decapoda: Paguroidea: Diogenidae), Zootaxa 831, pp. 1-42 : 28-32

Pseudopaguristes gracilis n. sp. ( Figs. 10 , 11 )

Material examined. Holotype: 1 male, 3.5 mm, southeast of Karang Kaledupa, Snellius II, stn. 24, 05°57'S, 123°49'E, 350–500 m, 9 Sep 1984 ( MZB). Paratypes: 1 male 3.5 mm, KARUBAR, stn. DW 14, 05°18'S, 132°38'E, 24 Oct 1991, 245– 246 m ( MNHN Pg 5933); 1 male 2.0 mm, 1 female 1.4 mm, KARUBAR, stn. DW 18, 05°18'S, 133°01'E, 205–212 m, 24 Oct 1991 ( MNHN); 1 female 1.3 mm, KARUBAR, stn. DW 50, 07°59'S, 133°02'E, 184–186 m, 29 Oct 1991 ( MNHN); 2 males 1.3, 1.5 mm, Madura Bay, Siboga , stn. 51, 69– 91 m, 19 Apr 1899 ( ZMA).

Description. Biserial phyllobranchiae. Shield ( Fig.10 a) slightly longer than broad; several tubercles anterolaterally; dorsal surface slightly convex, with scattered short setae. Rostrum broadly triangular, rounded at apex, slightly produced beyond base of ocular acicles; shorter than generally pointed lateral projections. Ocular peduncles stout, approximately 0.6 length of shield, swollen proximally. Corneas slightly dilated, diameter of corneas 0.1–0.2 length of ocular peduncles. Ocular acicles moderately large, separated basally, distal parts triangular and blunt at apices, mesial borders convex. Subquadrate calcified interocular lobe with 3–4 rounded spinules anteriorly. Antennular peduncles exceeding ocular peduncles by 0.7–0. 8 of ultimate segments; basal segment with small spine distomesially and distolaterally. Antennal peduncles reaching midlength of corneas; fifth segment with small spine mesially; fourth and third segments strongly produced at dorsodistal angle, terminating acutely; second segment with dorsolateral distal angle produced, terminating in pointed spine; dorsomesial distal angle with small spine; first segment short, unarmed. Antennal flagellum about 0.6 length of shield, consisting of 9 to 10 articles; each article with few short setae.

Third maxilliped with small spine on ventrodistal margin of ischium; ventral margin of merus with 4 spines and 1 spine distodorsally; carpus, propodus and dactyl unarmed.

Chelipeds subequal ( Figs. 10 b–e), armature generally similar. Ischia each with row of small spines on ventromesial margin. Meri each with row of spines on dorsal margin, stronger distally, 1 distal transverse row of spines extending mesially and laterally; lateral faces with sparse minute tubercles, mesial faces smooth; ventromesial margins each with row of rather strong spines distally, minute spines proximally; ventrolateral margins each with row of weak spines. Carpi slightly more than half length of meri, dorsomesial margins each with 4 strong spines, dorsal surfaces each with 1 or 2 irregular rows of small, widely­spaced spines and few tufts of setae. Palms approximately 1.5 length of carpi, dorsomesial margins each with 4 strong conical spines, dorsal surfaces relatively smooth proximally, strong spines or conical tubercles distally, tending to form 3 longitudinal rows of widely­spaced spines, 2 rows continued to fixed finger, becoming smaller and closelyspaced conical tubercles and with few tufts of setae; mesial faces each with two prominent spines adjacent to ventral margin; cutting edge of fixed finger with large teeth, terminating in corneous claw. Dactyls approximately 1.5 length of palms; dorsomesial margins each with row of spinules, dorsal surfaces each with 2 irregular longitudinal rows of widelyspaced tubercles, mesial surfaces each with 4 tubercles in distal half medially, longitudinal row of tuft of setae near ventral margin, several scattered tubercles near dorsal margin; cutting edge with row of large calcareous teeth proximally, smaller teeth distally, terminating in small corneous claw; dactyl and fixed finger with small hiatus. All surface covered with sparse setae.

Second and third pereopods slender, longer than chelipeds; similar from left to right. Meri of second pereopods ( Fig. 11 a) with ventral margins each bearing 2–3 small spines distally. Carpi approximately 0.7–0.8 length of meri, each with 5 irregular spines on dorsal margins, lateral faces each with shallow longitudinal groove. Propodi considerably longer than carpi; each with row of 6 (left) or 8 (right) strong spines on dorsal margin subdistally and tufts of long setae; ventral margins with row of spinules (left) or smooth (right) and sparse setae; lateral faces each with shallow longitudinal groove and tufts of setae medially. Dactyls very slightly curved, 1.6 length of propodi, each terminating in strong corneous claw; ventral margins each with row of corneous spines distally, long setae along each dorsal and ventral margin.

Third pereopod ( Fig. 11 b, c) with meri unarmed (left) or with small spinules on dorsal margin (right). Carpi 0.8 length of meri, each with strong spine at dorsodistal angle and tufts of plumose setae along each dorsal and ventral margin. Propodi considerably longer than carpi, unarmed; lateral faces each with shallow longitudinal groove medially, dorsal and ventral margins with tufts of plumose setae. Dactyls 1.4 length of propodi, each terminating in strong corneous claw; dorsal and ventral margins each with row of corneous spines distally; tufts of long setae on each dorsal and ventral margin; mesial surfaces each with longitudinal row of corneous spines on distal half medially, and sparse setae. Fourth pereopod ( Fig. 10 f) without preungual process; propodi each with 2 rows of corneous scales in propodal rasp.

Male first pleopods ( Fig. 10 g) small; inferior lamella rounded, distal margin with row of hook­like spines. External lobe with triangular tip, separated from internal lobe by shallow cleft; internal lobe rounded, curved towards inferior lamella. Unpaired left pleopods 3 to 5 uniramous. Female with paired gonopores; brood pouch absent.

Telson ( Fig. 10 h) subquadrate, left lobe slightly longer than right. Each lobe of holotype armed with 4 (left) or 5 (right) strong spines. Lobes in paratype each armed with 3 or 5 (left) and 3 or 4 (right) small spines.

Etymology. From latin gracilis meaning slender, reflecting the slenderness of the second and third pereopods.

Habitat. This species was collected from substrate with calcareous stones, dead coral and sponges.

Distribution. South Sulawesi, Madura Bay and Kai Island, Indonesia.

Remarks. Morphological character variation in P. gracilis appears to size related. The holotype is the largest specimen in the collection. In smaller individuals, the calcified interocular lobe is armed with subacute spinules anteriorly; the antennular peduncles are shorter; the antennal acicles have more spinules; and the chelipeds are more robust.

This species resembles Pseudoguristes laurentae ( Morgan & Forest, 1991) in general shape and spination of the chelipeds and ambulatory legs and in the form of the ocular peduncles, which are swollen proximally. The shape and spination of the telson separates the two species. P. gracilis bears four or five spines on the terminal margin of each lobe while in P. laurentae the terminal margin of each lobe is armed only with two or three strong spines. The presence of a subquadrate interocular lobe and two prominent spines on the mesial face of palm in P. gracilis also immediately distinguishes it from P. l a u re n t a e.

Figures

FIGURE 10. Pseudopaguristes gracilis n. sp., holotype, male 3.5 mm (MZB): a, shield and cephalic appendages, setae omitted; b – e, left cheliped, setae omitted; f, left fourth pereopod, setae omitted; g, right first pleopod, setae omitted; h, telson; b, mesial view; c, dorsal view; d, merus (lateral view); e, dactyl (mesial view); g, external view. Scales equal 1 mm.

FIGURE 11. Pseudopaguristes gracilis n. sp., holotype, male 3.5 mm (MZB): a. left second pereopod, setae omitted; b, c, left third pereopod, setae omitted; a, c, lateral view; b, mesial view. Scale equals 1 mm.