Sundathelphusa niwangtiil, Husana & Kase & Mendoza, 2015

Husana, Daniel Edison M., Kase, Tomoki & Mendoza, Jose Christopher E., 2015, Two new species of the freshwater crab genus Sundathelphusa Bott, 1969 (Crustacea: Brachyura: Gecarcinucidae) from Negros Island, Philippines, Raffles Bulletin of Zoology 63, pp. 226-236 : 231-235

publication ID	https://doi.org/ 10.5281/zenodo.4504208
publication LSID	lsid:zoobank.org:pub:549829D6-65A9-4D97-B15E-361755F7577B
persistent identifier	https://treatment.plazi.org/id/B34745CF-F240-485E-BDF6-71AE0081302D
taxon LSID	lsid:zoobank.org:act:B34745CF-F240-485E-BDF6-71AE0081302D
treatment provided by	Carolina
scientific name	Sundathelphusa niwangtiil
status	sp. nov.

Treatment

Sundathelphusa niwangtiil View in CoL , new species

Figs. 5–8 View Fig View Fig View Fig View Fig

Material examined. Holotype, ♂ (16.6× 13.5 mm) ( NMCR 39112 ), Mambaho Cave , Mabinay town, Negros Oriental province, Negros I., Philippines, 09°40.157’N, 122°59.122’E, GoogleMaps

coll. DEM Husana, 26 August 2009. Paratypes: 1 ♂ (19.3× 15.5 mm), 1 ♀ (23.0× 17.6 mm, with 33 juveniles in brood cavity) ( ZRC 2014.0239 View Materials ), same data as holotype GoogleMaps ; 6 ♀ (16.6× 13.7 mm – 24.5× 19.2 mm) (NSMT-Cr 22936), same data as holotype GoogleMaps

Description. Carapace ( Figs. 5A View Fig , 6A View Fig , 7A, H View Fig ) subquadrate to cardioid in outline, about 1.2–1.3 times broader than long, widest at level of mesobranchial region; dorsal surface gently convex longitudinally, transversely; branchial region moderately inflated, cardiac, intestinal regions flat; epigastric, postorbital cristae low but distinct, more-or-less confluent; lateral regions with weak striae; distinct median groove between epigastric regions, cervical groove shallow, H-shaped gastric groove distinct. Front moderately broad, about 0.23–0.26 times greatest carapace width, gently deflexed ventrally; anterior margin with broad median concavity in dorsal view; frontal median triangle ( Fig. 7D View Fig ) distinct, but in holotype, nearly-straight dorsal margin not completely fusing with lateral margins. External orbital angle triangular, external margin cristate, almost straight, distinctly longer than internal margin; epibranchial tooth small but distinct, triangular, well separated from external orbital tooth by U-shaped notch. Anterolateral margin cristate, gently convex, slightly serrated; posterolateral margin nearly straight, converging gradually towards posterior margin of carapace; central region of posterior margin slightly concave. Orbital margins cristate, supraorbital margin smooth, infraorbital margin slightly serrated. Suborbital, subbranchial, pterygostomial regions moderately rugose, with scattered, varied rows of small granules. Posterior margin of epistome ( Fig. 7E View Fig ) with protruding, sharply triangular median lobe, separated from sinuous lateral lobes by distinct clefts.

Eyes ( Figs. 5C View Fig , 6B View Fig ) large, occupying almost entire orbit, corneas well developed. Third maxilliped ( Figs. 5B, C View Fig , 6B View Fig , 7B View Fig ) sparsely setose; ischium subrectangular, with distinct, oblique, submedian sulcus closer to mesial margin; merus subquadrate, anterior margin gently concave, lateral margin convex; exopod slender, tapering distally, external margin slightly sinuous, distal tip reaching level of mid-length of merus, flagellum well-developed, reaching slightly beyond mesial margin of merus.

Male thoracic sternum ( Fig. 5B View Fig , 7F View Fig ) broad, generally smooth except for slightly granular anterior region; sternites 1–4 fused, traces of sutures between sternites 2, 3 and 3, 4 as shallow depressions; sternite 4 lateral margins straight, slightly raised area around anterior portion of sternoabdominal cavity. Sterno-abdominal cavity deep; press-button on sternite 5, midway between sutures.

Chelipeds, P1 ( Figs. 5A View Fig , 6A View Fig ), subequal, noticeably elongated, more robust in males; anterior margin of merus lined with large, conical granules; carpus ( Fig. 7C View Fig ) slightly rugose with rows of low granules, inner angle with strong, sharply pointed tooth, followed by two smaller teeth posteriorly; palm slightly inflated, with minutely granular outer surface; fingers slender, cutting edges armed with many sharp teeth with large tooth at some intervals.

times median length, distal tip reaching to level of posterior quarter of P1 coxae in ventral view.

G1 ( Figs. 8A, B View Fig , D–I) moderately stout, tapering distally, straight to slightly curved laterally, mesial margin nearly straight, lateral margin concave; terminal segment about 0.43 times length of subterminal segment, subconical, distal tip narrow. G2 ( Fig. 8C View Fig ) slender, tapering distally; terminal segment long, about 0.41 times length of subterminal segment.

Ambulatory legs, P2–P5 ( Figs. 5A View Fig , 6A View Fig , 7I, J View Fig ), long, slender, P3 longest, total length (coxa-dactylus) about 1.7 times maximum carapace width, P5 shortest, total length (coxadactylus) about 1.4 times maximum carapace width; anterior margins of meri distinctly serrated, with low subdistal tooth, posterior margins smooth on all legs; carpi short, with longitudinal submedian ridge on dorsal surface except for P5, widened distally; propodi flattened, margins serrated; dactyli slender, subequal in length to propodi, spiniform, marginal setae short.

Male pleon ( Fig. 5B View Fig , 7G View Fig ) inverted T-shaped, relatively broad for the genus; somite 1 thin, sinuous; somites 2–5 subtrapezoidal, progressively narrowing distally; somite 6 subquadrate, median length subequal to greatest width (distal end), lateral margins slightly concave; telson subtriangular, apex rounded, lateral margins concave, basal width about 1.2 Variation. The type series consists of two males and seven females, with the holotype (NMCR 39112) being the smaller of the two males. The larger specimens tend to have more laterally expanded carapaces ( Figs. 6 View Fig , 7H View Fig ), and a more complete frontal triangle ( Fig. 6B View Fig ), with the dorsal margin dorsally convex and meeting the lateral margins, compared to those of the holotype. The larger male paratype (ZRC 2014.0239) also has a much broader pleon, a more curved G1 than seen in the holotype, and an extra pair of pleopods (on pleonal somite 3) that resemble the G 2 in form. As such, it was not selected as the holotype despite its larger size, and is deemed to be an aberrant form of this species. Other than this, the females vary from the males in the usual sexually dimorphic characters (e.g., chelipeds, pleon, genitalia).

Colouration. The live colouration of the carapace of Sundathelphusa niwangtiil , new species, ranges from pale yellow to pale brown. Legs and ventral surface of the body are lighter in colour on all specimens.

Etymology. The specific epithet is derived from the arbitrary combination of two words in the Visayan language, “nīwáng” (adj., slender) and “tiíl” (n., leg), in allusion to the long and slender legs of this species. Used as a noun in apposition. Remarks. Sundathelphusa niwangtiil , new species, is most similar to S. holthuisi Ng, 2010 , in their general appearance, especially the shape of the carapace. They differ, however, in the following morphological features: 1) the central projection of the epistome is more pointed at the tip in S. niwangtiil ( Figs. 5C View Fig , 6B View Fig , 7E View Fig ) (more rounded in S. holthuisi ; cf. Ng, 2010: fig. 3B); 2) the ambulatory legs of S. niwangtiil ( Figs. 5A View Fig , 6A View Fig , 7I, J View Fig ) are noticeably more slender, particularly the meri, than those of S. holthuisi (cf. Ng, 1991: figs. 1A, C; Ng, 2010: fig. 2B); 3) the male pleon is relatively wider and shorter in S. niwangtiil ( Fig. 7G View Fig ) (more slender and longer in S. holthuisi ; cf. Ng, 1991: fig. 4A; Ng, 2010: fig. 4D); 4) the G1 of S. niwangtiil ( Fig. 8A, B, D, E View Fig , F–I) is stouter, especially at the base, with the terminal segment relatively straighter and more conical (G1 more slender, with terminal segment more curved and subcylindrical in S. holthuisi ; cf. Ng, 1991: fig. 4B–E; Ng, 2010: fig. 4J–L, M); and 5) the colouration of the live specimen of this new species ranges from uniformly pale yellow to pale brown (DEMH, pers. obs.), while S. holthuisi has a light red carapace and dark purple ambulatory legs (viz. Ng, 1991; Ng, 2010).

Sundathelphusa niwangtiil , new species, is also similar to S. sutteri ( Bott, 1970) (type locality: Baguio, Luzon), in the carapace shape and proportions of the ambulatory legs, particularly when comparing the larger female paratypes of the former to the sole type specimen (a female) of the latter (cf. Bott, 1970: pl. 15 figs. 73–75; see also clarification by Ng, 1991: 5, 16). The two species can be distinguished, however, by the following: 1) in dorsal view, the frontal margin is slightly advanced or level with the tips of the external orbital tooth in S. niwangtiil ( Figs. 5A View Fig , 6A View Fig , 7A View Fig ) (tips of external orbital teeth more advanced than front in S. sutteri , giving the fronto-orbital margin a distinctly concave aspect; cf. Bott, 1970: pl. 15 fig. 73); and 2) the anterolateral margins of the carapace are relatively less convex and laterally less expanded in S. niwangtiil ( Figs. 5A View Fig , 6A View Fig , 7A View Fig ) (more convex and laterally more expanded in S. sutteri (cf. Bott, 1970: pl. 15 fig. 73).

Although the two new species are from the same island, S. niwangtiil can readily be distinguished from S. orsoni by the following: 1) the carapace is relatively broader and the branchial, suborbital and pterygostomian surfaces, as well as the external surfaces of the cheliped carpi, are distinctly less rugose in S. niwangtiil ( Figs. 5 View Fig , 6 View Fig , 7A, C, H View Fig ) (carapace narrower, more strongly rugose in S. orsoni ; Figs. 1 View Fig , 2 View Fig , 3A, C View Fig ); 2) the epigastric and postorbital cristae are relatively low, weak, and not distinctly confluent in S. niwangtiil ( Figs. 5A, C View Fig , 6 View Fig , 7A, H View Fig ) (well-defined, sharp, and distinctly confluent in S. orsoni ; Figs. 1A, C View Fig , 2 View Fig , 3A View Fig ); 3) the male anterior thoracic sternum is relatively broader, with the lateral margins of sternites 1–3, and 4 more sinuous in S. niwangtiil ( Figs. 5B View Fig , 7F View Fig ) (male anterior thoracic sternum narrower in S. orsoni , with lateral margin of sternites 1–3 straight, and of sternite 4 convex; Figs. 1B View Fig , 3F View Fig ); 4) the male pleon of S. niwangtiil is distinctly wider ( Fig. 7G View Fig ) (male pleon narrower in S. orsoni ; Fig. 3G View Fig ); 5) the ambulatory legs, particularly the meri, are relatively more slender in S. niwangtiil ( Figs. 5A View Fig , 6A View Fig , 7I, J View Fig ) (stouter in S. orsoni ; Figs. 1A View Fig , 2A View Fig , 3H, I View Fig ); 5) in S. niwangtiil the G1 is much stouter at the base, the terminal segment is less curved and its tip is more tapered ( Fig. 8A, B, D, E View Fig , F–I) (G1 more slender, terminal segment more distinctly curved, with tip broader, in S. orsoni ; Fig. 4A, B, D, E View Fig ); and 6) the live colouration of S. niwangtiil is pale yellow to pale brown (dark to blackish brown in S. orsoni ).

The type specimens of S. niwangtiil , new species, were collected under rocks inside Mambaho Cave in the municipality of Mabinay, Negros Oriental province. The cave also has a flowing subterranean stream. The source and sink of this river were submerged in water and inaccessible at the time of collection. Aside from the cave’s main entrance, the cave also has another opening at the ceiling about 100 meters from the main.