Stratiotes ngochoae, 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 : 20-24

Stratiotes ngochoae n. sp. ( Figs. 8 , 9 )

Material examined. Holotype: male, 3. 8 mm, Taruna bay, Sangir Besar (Great Sangir) Island, Siboga , stn. 127, 45 m, 20–21 Jul 1899 ( ZMA). Paratype: 1 male, 4.9 mm, type locality ( ZMA)

Description. Biserial phyllobranchiae. Shield ( Fig. 8 a) 1.2 longer than broad; lateral margins sloping, short transverse row of small spines and tufts of setae on dorsal surface. Rostrum broadly triangular, distinctly overreaching lateral projections, terminating in acute spine. Lateral projections triangular, with acute marginal spine. Ocular peduncles stout, left slightly longer than right, 0.7–0.8 length of shield; swollen proximally, corneas less inflated; corneal diameter 0.3 of peduncular length; ocular acicles small, distinctly separated basally, terminating in bifid spine. Antennular peduncles, when fully extended, overreaching corneas; basal segment with distal acute spine dorsomesially and dorsolaterally, and median spine dorsolaterally. Antennal peduncles reaching nearly to bases of corneas; fifth and fourth segments unarmed; third segment with ventromesial distal angle strongly produced terminating in strong spine; second segment with dorsolateral distal angle produced, terminating in prominent bifid spine, subdistal spine on lateral margin, strong spine on distal margin; first segment unarmed. Antennal acicle not reaching distal margin of ultimate peduncular segment, terminating in prominent bifid spine, mesial margin with 2 strong proximal spines, lateral margin with 2 strong distal spines. Antennal flagellum slightly shorter than carapace, consisting of 15–17 articles, each article with short, sparse setae.

Basis of third maxilliped with 2 distoventral spines; merus with 5 small spines on ventral margin.

Chelipeds subequal ( Fig. 9 a–d), armature similar. Ventromesial margins of ischia each with row of moderately strong spines. Meri each with row of strong spines on dorsal margin, weaker spines proximally; ventromesial margins each with row of strong spines, less prominent spines on ventrolateral margins, partially obscured by dense plumose setae; mesial faces glabrous, lateral faces with scattered small tubercles. Carpi each with row of corneous­tipped spines on dorsomesial margin; dorsal surfaces each with 1 row of moderately small spines near dorsomesial margin, second row of moderately larger spines medially; small spines on distal margin and tufts of setae. Palms 0.7 length of carpi, dorsomesial margins each with 3 strong, corneous­tipped spines; dorsal surfaces with several irregular rows of large, occasionally corneous­tipped spines, becoming closely­spaced on fixed finger; ventral surfaces each with single row of corneous spines medially, extending to fixed finger; cutting edge with small calcareous teeth terminating in moderately large corneous claw; dorsal and lateral surfaces of palm and fixed finger covered with long setae. Dactyls approximately twice length of palms; dorsomesial margins each with row of small, corneous­tipped spines; dorsal surfaces with scattered small spines, tufts of setae on entire dorsal surfaces; mesial surfaces each covered with small corneous spines, more or less arranged in traverse rows, accompanied by tufts of setae; cutting edge with small calcareous teeth, terminating in small corneous claw, no hiatus between dactyl and fixed finger.

Left and right second and third pereopods similar. Ischia of second pereopods ( Fig. 9 e, f) each with distal spines on ventromesial and dorsal margins. Meri each with row of small spines on ventrolateral margin, stronger row of spines on ventromesial margin; long setae on dorsal and ventral margins. Carpi approximately 0.7 length of meri, each with dorsal row of 9 or 10 irregular strong spines; lateral faces convex, each with longitudinal sulcus near dorsal margin accompanied by 2 distal spines and long setae. Propodi slightly longer than carpi, each with dorsal row of 8 large corneous­tipped spines; ventral margins each with denticles; mesial surfaces each with row of setae near ventral margins. Dactyls 1.2 length of propodi, dorsal margins each with row of corneous spines and tufts of setae; mesial surfaces each with row of small spiniform setae near ventral margins and scattered setae; ventral margins each with row of small spiniform setae, stronger distally.

Third pereopods ( Figs. 9 g, h) each with distal spine on ventromesial margin of ischium. Meri each with row of spines or spinules on dorsal margin; ventromesial margins each with row of spines and long setae; ventrolateral margins each with 2 spinules medially. Carpi slightly shorter than meri, each with irregular spines on dorsal margin, distal spine strongest; lateral surfaces convex, each with longitudinal sulcus near dorsal margin accompanied by 2 distal spines and long setae. Propodi each with minutely spinulose dorsal surface; lateral faces glabrous; mesial surfaces each with transverse striae consisting of 2 or 3 small corneous­tipped spines, concealed at least partially by dense setae. Dactyls almost 1.4 longer than propodi; dorsal margins each with row of minute spinules and long setae; mesial faces each with irregular rows of spiniform setae and long simple setae; lateral and mesial faces each with narrow longitudinal sulcus proximally; ventral margins each with spiniform setae and long, simple setae. Fourth pereopods with preungual process ( Fig. 9 i).

Male first pleopods ( Figs. 8 d, e) robust; inferior lamella rounded, distal margin with several rows of hook­like spines. External lobe elongate, tip slightly curved, separated from internal lobe by shallow cleft; internal lobe rounded, broad. Female unknown.

Telson with posterior lobes asymmetrical, separated by wide cleft; right lobe much smaller (holotype) ( Fig. 8 b); right lobe only slightly smaller than left (paratype) ( Fig. 8 c). Terminal margin of left lobe with 10 spines (holotype) or 7 strong spines (paratype); right lobes with row of 4 (holotype) or 6 (paratype) strong corneous spines, extending onto lateral margins.

Etymology. Dedicated to Dr Nguyen Ngoc­Ho who has contributed so much to our knowledge of the anomuran fauna.

Habitat. The specimens were collected from fine sand substrate.

Distribution. North of Sulawesi, Indonesia.

Remarks. The dissimilarity between left and right lobes of the telson of the holotype seems to be an anomaly. The telson of the paratype is considered the normal form.

S. ngochoae n. sp. most closely resembles S. breviantennatus n. sp. in the general shape of the chelipeds and the first male pleopods, and in the armature of the pereopods. Differences between these two species are apparent in the armature of the mesial faces of the dactyls of the chelipeds and the form and spination of the telson. In S. breviantennatus the mesial faces of the dactyls of the chelipeds are armed with a few moderately large, corneous spines, whereas in S. ngochoae they are covered with dense, small corneous spines. The telson of S. breviantennatus is armed with row of tiny spinules on the terminal margins of both lobes and three larger spines on the lateral margin of the left lobe. In S. ngochoae , the telson has larger, corneous­tipped spines extending onto the lateral margins. Furthermore, the ocular acicles of S. ngochoae are bifid, whereas in S. breviantennatus they are simple.

Figures

FIGURE 8. Stratiotes ngochoae n. sp., holotype, male 3.8 mm (ZMA): a, shield and cephalic appendages, setae omitted; b, c, telson. b. holotype; c, paratype, 4.9 mm; d, e, right first pleopod, setae omitted; d, external view; e, internal view. Scales equal 1 mm.

FIGURE 9. Stratiotes ngochoae n. sp., holotype, male 3.8 mm (ZMA): a – d, left cheliped, setae omitted; e, f, left second pereopod; g, h, left third pereopod; i, left fourth pereopod; a, dorsal view; b, merus (mesial view); c, dorsolateral view; d, dactyl (mesial view); e, g, mesial view; f, h lateral view. Scales equal 1 mm.