Lithoselatium pulchrum, Schubart, Christoph D., Liu, Hung-Chang & Ng, Peter K. L., 2009

Schubart, Christoph D., Liu, Hung-Chang & Ng, Peter K. L., 2009, Revision of Selatium Serène & Soh, 1970 (Crustacea: Brachyura: Sesarmidae), with description of a new genus and two new species, Zootaxa 2154, pp. 1-29 : 15-20

Lithoselatium pulchrum n. sp.

( Figs. 9–12 )

Material examined. Taiwan: Holotype male (23.5 x 20.8 mm) ( ZRC 2002.0152), Yakoulu, Manchou, Pingtung County, Taiwan, rocky shore with tide pools, coll. H.-C. Liu, 27 August 1999 ( DNA voucher); paratypes: 1 female (23.2 x 20.1 mm with eggs) ( ZRC 2002.0152), same data as holotype; 1 female (18.1 x 15.7 mm), Chuanfanshih, Hengchun, Pingtung County, Taiwan ( ZRC 1999.0555), coll. P. K. L. Ng et al., 31 May 1997; 2 females (25.7 x 22.5 mm, 18.7 x 16.1 mm), 1 ovigerous female (25.1 x 22.1 mm) (HC Liu, to be deposited at TMCD), Yakoulu, Manchou, Pingtung County, Taiwan. coll. H.-C. Liu, 29 August 1999; 1 female (23.5 x 20.3 mm) (HC Liu, to be deposited at TMCD), Yakoulu, Manchou, Pingtung County, Taiwan. coll. H.-C. Liu, 25 May 1999; 3 females (23.3 x 19.9 mm, 22.3 x 19.5 mm, 19.3 x 16.2 mm), 1 ovigerous female (23.3 x 20.0 mm) (HC Liu, to be deposited at TMCD), Yakoulu, Manchou, Pingtung County, Taiwan. coll. H.-C. Liu, 27 August 1999; 1 male (18.1 x 15.1 mm) ( NTOU), Chuanfanshih, Hengchun, Pingtung County, Taiwan, coll. P.-H. Ho, 2004.

Type locality. Taiwan, Pingtung County, Manchou.

Diagnosis. Carapace trapezoidal, lateral margins distinctly diverging posteriorly; lateral margins entire without epibranchial tooth, but occasionally 1 or 2 low granules ( Fig. 10 A, B); frontal margin with 2 low, gently convex lobes not produced anteriorly, posterior lobes distinct ( Fig. 10 A, B,); outer inner surfaces of chelae finely granular ( Fig. 11 B); dorsal margin of palm with continuous longitudinal crest of proximal tubercles, followed by pectinated crest consisting of 36 or 37 teeth, approximately 5 distal tubercles; 3–5 short, oblique rows of tubercles on inner side ( Fig. 11 C); dorsal margin of dactylar finger with row of 34 or 35 tubercles; all tubercles broad with exception of proximal 2, dome-shaped, transversely striated with yellow apex in life, becoming more widely spaced towards distal ( Fig. 11 D); cutting edge of dactylus with 2 or 3 larger teeth proximally, larger tooth subdistally; cutting edge of pollex with 2 or 3 larger teeth medially, larger tooth subdistally ( Fig. 11 B.); G1 with pectinated distal part; subtruncate tip with slight cleft, lower part larger than upper ( Fig. 12 D–G).

Description of male holotype. Carapace trapezoidal, lateral margins distinctly diverging toward posterior margin; dorsal surfaces smooth, regions well defined by distinct grooves; surface adjacent to anterolateral margins lined with weak, oblique striae; gastrocardiac surface with distinct groove. Postfrontal lobes distinct; 2 median lobes larger with finely granular margins, without clearly visible anterior ridge; 2 lateral lobes low with finely granular margins; lobes separated by distinct grooves. Front strongly deflexed downwards, with 2 low, gently convex lobes separated by broad, shallow cleft, not strongly produced anteriorly. Supraorbital margin entire. Anterolateral margin entire, confluent with posterolateral margin, without epibranchial tooth; 1 or 2 very low granules may mark rudimentary teeth. Posterolateral margin gently diverging towards convex posterior carapace margin. Epistome with pronounced horizontal ridge, medially concave; posterior margin with median triangular projection, lateral part with 2 concave indentations. Verwey’s groove delimited by dorsal and ventral rows of setae. Infraorbital ridge tuberculate, evenly setose. Pterygostomial region tuberculate, covered by distally curved setae. Antenna entering orbit; basal segments of antenna and antennules not separated by septum; basal antennal segment mobile. Ischium of third maxilliped with shallow submedian sulcus; merus subovate with distinct submedian longitudinal setose ridge extending to anteroexternal angle of ischium; exopod slender, with long flagellum.

Chelipeds equal in size and shape. Outer surface of chelae slightly granular, inner surface with fewer, somewhat coarser granules, without distinct transverse ridge; ventral border straight; dorsal margin of palm with continuous longitudinal crest of proximal tubercles, followed by pectinated crest consisting of 36 or 37 teeth and approximately 5 distal tubercles; 3–5 short, oblique subsidiary rows of tubercles on inner side; fingers long, more than half length of ventral margin of palm; dorsal margin of dactylus with row of 34 or 35 tubercles; all tubercles broad with exception of proximal 2, dome-shaped, transversely striated with yellow apex in life, becoming more widely spaced towards distal part; cutting edge of dactylus with 2 or 3 larger teeth proximally, larger tooth subdistally; cutting edge of pollex with 2 or 3 larger teeth medially, larger tooth subdistally; tips of fingers hoofed (medially excavated) with sharp cutting edges. Outer surface of carpus rugose; inner distal angle not distinctly produced, margins weakly granulated. Outer face of merus strongly convex, with rows of granules; inner face granular, strongly expanded distally, appearing foliaceous, with subdistal tooth on dorsal margin, distal margins lined with small granules or tubercles, distal portion dorsally visible, even when chelipeds apposed tightly against carapace; inner face with 2 longitudinal rows of stiff setae, ventral row continuous, with longer setae. Basis and ischium immobile but separated by distinct suture, surface with scattered granules.

Ambulatory legs long, third pair longest. Lateral margins of coxae of legs 1–3 with numerous short setae; lateral and ventral surfaces with dense long tufts of long setae; those on first leg concentrated on posterior portion, those of leg 3 on anterior portion, those of leg 2 densest and longest, covering surface. Outer surfaces of meri, carpi, propodi rugose. Meri laterally flattened, foliaceous, margins finely granulated; with low subdistal dorsal spine; outer part of postero-distal margin slightly expanded, anterior surface convex. Outer surface of carpi with 2 distinct carinae. Distal third of propodi with tufts of short setae dorsally and ventrally. Dactylo-propodal lock absent, propodal-dactylar condyle not enlarged. Dactylus elongate, distinctly longer than half length of propodi, densely setose dorsally and ventrally.

Margins of anterior thoracic sternites and surfaces of sternites 1–4 setose. Sternites 1, 2 completely fused, suture concave toward buccal cavity; suture 3/4 separated by complete suture; sutures 4/5, 5/6, 6/7, 7/8 medially interrupted, separated by wide gap; deep longitudinal median groove present on sternites 7, 8; male sterno-abdominal cavity almost reaching suture 3/4; part of sternite 8 clearly visible when male pleon fully closed. Penis partially calcified, sternal.

Abdomen triangular; lateral margins of abdominal somites 3 and 6 convex, lateral margins of somites 4, 5 gently concave. Telson subcircular, width and length subequal.

G1 relatively stout, subdistal part only slightly wider than median part, almost straight from ventral view; pectinated distal part prominently bifurcated, lower part larger than upper part. G2 very short, distally spatuliform, no distal segment present.

Females. Chelipeds of females also homochelous, but relatively small compared to male chelipeds; tubercles on dorsal margin of dactylus reduced. Pectinated crest on palm shorter with 16 or 17 broad teeth, longitudinal crest completed by row of tubercles. Margins of all abdominal somites in contact with bases of ambulatory legs; telson sunken into anterior margin of somite 6. Gonopores elevated, bilobed.

Colour. Carapace and legs purplish in life; carapace with yellowish-green mottling; chelae pink-red ( Fig. 9 ).

Ecology. Lithoselatium pulchrum n. sp. has so far only been collected from rocky shores in southern Taiwan. It constructs burrows in sandy areas between the rocks and can often be found in tide pools. The preferred habitat seems to be the surge channels of eroded and rugged limestone with many crevices and rock pools. The crab usually lives in crevices close to the supralittoral zone. The salinity of tide pools close to the burrows inhabited by L. pulchrum ranges from 0–33‰. Only three mature males have been found thus far (one not preserved), although females and juveniles are often seen. During a two-week collecting trip in 2007 by the second author, three immature males and 14 females (11 of them adult) were collected and most subsequently released. The smallest ovigerous female had a carapace width of 18.9 mm and the smallest mature female (determined by the morphology of abdomen) measured 17.0 mm. Two ovigerous females were observed at the surf zone about to release their larvae. Another two females were collected from the surf zone with eggs about to hatch. Ovigerous females were found from July to October.

In laboratory conditions, females bred between April and October. Two captive females became ovigerous twice without mating. It appears that even after ecdysis, the female can lay fertilized eggs without mating. A female collected in September 2007 moulted in February 2008, and became ovigerous in captivity in June 2008, in the absence of a male. Eggs of L. pulchrum are large and yolky, and hatch as highly developed larvae. Eggs in an early stage of development are relatively large and have a diameter of 1.09 ± 0.02 mm (n = 10). These eggs reached their maximum size of about 1.25 ± 0.04 mm (n = 11) just before hatching. The incubation was about 43 days under laboratory conditions of 19°–28°C. Ovigerous females only released their larvae at night, with the entire release process lasting only a few seconds. The number of hatched larvae varied between 525 and 1158 (n = 5), and was dependent on the size of the females, with fecundity directly increasing with size ( Kuo 2008).

Etymology. From Latin pulcher for “beautiful” used as an adjective, in reference to the pretty colour of the new species.

Figures

FIGURE 9. Lithoselatium pulchrum n. sp., colour in life. A, B, holotype male (23.5 x 20.8 mm) (ZRC 2002.0152), Taiwan; B, C. paratype male (18.1 x 15.1 mm) (NTOU), Taiwan. A, B, dorsal views; C, ventral view.

FIGURE 10. Lithoselatium pulchrum n. sp. Holotype male (23.5 x 20.8 mm) (ZRC 2002.0152), Taiwan. A, dorsal view; B, dorsal view of carapace; C, frontal view of carapace.

FIGURE 11. Lithoselatium pulchrum n. sp. Holotype male (23.5 x 20.8 mm) (ZRC 2002.0152), Taiwan. A, anterior thoracic sternum and abdomen; B, outer view of right chela; C, dorsal view of ridge on palm; D, ridge on dactylus of palm.

FIGURE 12. Lithoselatium pulchrum n. sp. Holotype male (23.5 x 20.8 mm) (ZRC 2002.0152), Kenting, Taiwan. A, abdomen; B, left third maxilliped (denuded); C, left side of anterior thoracic sternum; D, dorsal view of left G 1 (denuded); E, ventral view of left G 1 (denuded); F, dorsal view of distal part of left G 1 (denuded); G, ventral view of distal part of left G 1 (denuded); H, left G 2 (denuded).