Parahelice ngankeeae, Hsu & Shih, 2024

Hsu, Jhih-Wei & Shih, Hsi-Te, 2024, First records of Parahelice K. Sakai, Türkay & Yang, 2006 and Pseudohelice K. Sakai, Türkay & Yang, 2006 from Vanuatu, with description of a new species of Parahelice (Crustacea: Brachyura: Varunidae), Zootaxa 5476 (1), pp. 138-151 : 141-144

Parahelice ngankeeae sp. nov.

( Figs. 1 , 2 )

Type material. Holotype: male (24.3 × 19.1 mm), ZRC 2023.0238 , st. H4, shoreline behind Vanuatu Maritime College, W of Sarakata River mouth, Luganville Sanma Province, Espiritu Santo Island , Vanuatu, coll. P.K.L. Ng, S.H. Tan, H.H. Tan and J.C.E. Mendoza, 10 Sep. 2006 . Paratypes: 1 male (12.9 × 10.2 mm), ZRC 2023.0239 , same locality and collectors as holotype, 9 Sep. 2006 ; 1 male (17.0 × 13.4 mm), 1 female (22.7 × 17.6 mm), ZRC 2023.0240 , same locality and collectors as holotype, 10 Sep. 2006 ; 1 male (20.9 × 17.1 mm), 1 female (23.9 × 18.7 mm), ZRC 2023.0241 , same locality and collectors as holotype, 10 Sep. 2006 ; 1 male (23.8 × 18.6 mm), 1 female (24.5 × 18.8 mm), ZRC 2023.0242 , same locality and collectors as holotype, 11 Sep. 2006 ; 3 males (17.6 × 14.6, 14.9 × 12.0, 13.2 × 10.8 mm), 1 female (15.6 × 12.8 mm), ZRC 2023.2043 , same locality and collectors as holotype, 10 Sep. 2006 ; 1 male (20.0 × 16.2 mm), ZRC 2023.0244 , st. VM34, Palikulo Peninsula , Sanma Province, Espiritu Santo Island, Vanuatu, 23 Sep. 2006 .

Diagnosis. Carapace ( Figs. 1A, C, E, F , 2A ) quadrate, 1.22–1.29 times as broad as long; surface convex, irregularly punctated and finely granulated. Front broad, frontal margin slightly concave in both dorsal and anterior views; postfrontal region separated into 2 lobes.Anterolateral margins with 3 distinct teeth including external orbital tooth. Suborbital crista ( Fig. 2B, C ) sexually heteromorphic; in male ( Fig. 2B ), mesial part with 6–9 small rounded tubercles, followed by several (16–25) larger, elongated and fused tubercles, ending with 1 elliptical tubercle, lateral part with 1 largest, very convex elliptical tubercle, followed laterally by 2 or 3 smaller tubercle; in female ( Fig. 2C ), mesial part with 5 or 6 small rounded tubercles, followed by several (7–12) larger, elongated and mostly unfused tubercles, lateral part with 2 or 3 more convex, larger elliptical tubercles, ending with 1 or 2 small rounded tubercles. Chelipedal palm bulky in male, smaller in female; inner surface glabrous; outer surface with distinct patch of setae at base of fingers in male ( Fig. 2D ); only line of short setae at base of occlusal margin of immovable finger in female ( Fig. 2E ). Ambulatory legs slender, anterior margins of meri, carpi, and propodi covered with short setae. Male pleon ( Fig. 2F ) narrow, distal margin of telson not concave. G1 ( Fig. 2H–M ) slender, slightly curved, tapering, distal part curved laterally and ventrally; tip chitinous, chitinous endpiece shorter, wider and thicker. Female vulvae ( Fig. 2N ) with elongated semicircular sternal cover.

Description. Carapace ( Fig. 2A ) quadrate, slightly broader than long, 1.22–1.29 times as broad as long; surface convex, irregularly punctated and finely granulated; meso- to protogastric regions convex, with longitudinal deep groove; H-shaped gastro-cardiac groove prominent. Front broad, sloping forward; frontal margin lined with small, rounded granules, slightly concave in both dorsal and anterior views; postfrontal region slightly separated into 2 convex lobes. Supraorbital margins and anterolateral margins lined with small granules. Anterolateral margins with 3 distinct teeth including external orbital tooth; first tooth (external orbital tooth) largest, broad, slightly sloping forward; second tooth slightly narrower and sharper than preceding; last tooth smallest, distinct, acute. Posterolateral margins slightly convergent posteriorly; posterolateral regions regularly furnished with short setae.

Suborbital crista ( Fig. 2B, C ) sexually heteromorphic; in male, mesial part with several (6–9) less interspaced small rounded tubercles, followed by several (16–25) larger, elongated, less convex and fused tubercles, ending with 1 significantly larger and convex elliptical tubercle, lateral part with 1 significantly largest, very convex and elliptical tubercle, followed laterally by 1 large convex elongated tubercle and 1 or 2 small, convex, rounded tubercle ( Fig. 2B ); in female, mesial part with several (5 or 6) less interspaced small rounded tubercles, followed by several (7–12) larger, less convex elongated and mostly unfused tubercles, lateral part with well-spaced 2 or 3 more convex, larger elliptical tubercles, ending with 1 or 2 small rounded tubercles ( Fig. 2C ).

Chelipeds ( Fig. 1 ) usually unequal in adult male and equal in female. Merus without spines, dorsal and ventral margins glabrous. Surface of carpus glabrous, margins of carpus with dense short setae, inner distal angle with 1–3 tiny teeth. Palm bulky; inner surface almost smooth, glabrous; outer surface almost smooth; in male ( Fig. 2D ), distinct patch of setae at base of fingers, mostly expanding onto fixed finger, in both chelae; in female ( Fig. 2E ), only line of short setae present at base of occlusal margin of immovable finger.

Ambulatory legs ( Fig. 1 ) slender, anterior margins of merus, carpus, and propodus covered with short setae, posterior margins with sparse short setae.

Male pleon ( Fig. 2F ) narrow, surface smooth, without any granules, lateral margins lined with short setae; telson tongue-shaped, short than sixth somite, distal margin of telson not concave.

G1 ( Fig. 2 H–M ) slender, slightly curved towards lateral, tapering, distal part curved laterally and ventrally; tip chitinous, chitinous endpiece shorter, wider and thicker, genital pore widely open distally towards laterally and dorsally.

Female vulvae ( Fig. 2N ) with elongated semicircular sternal cover; sunken on inner part.

Etymology. The species is named after the late Dr. Ngan Kee Ng for her contribution to the taxonomy of brachyurans, especially the family Varunidae ( Lee & Jaafar 2022) .

Ecological notes. This species is common in mangrove and intertidal areas with sandy sediments (J. C. E. Mendoza, personal communication).

Distribution. Only known from Vanuatu.

Size. Largest male 24.3 × 19.1 mm (ZRC 2023.0238); largest female 24.5 × 18.8 mm (ZRC 2023.0242).

Remarks. Among the males of species in Parahelice and Pseudohelice , Par. georgei and all three species of Pseudohelice ( Pse. annamalai , Pse. latreillii , and Pse. subquadrata ) can be easily distinguished from remaining four Parahelice species by the absence of a patch of setae in Par. georgei and Pseudohelice species [vs. with patch of setae in other Parahelice species] (K. Sakai et al. 2006; Hsu et al. 2022; Prema et al. 2022; this study). In this regard, Par. ngankeeae sp. nov. resembles Par. balssi , Par. daviei , Par. pilimana and Par. pilosa , but can be separated by the characters of the suborbital cristae and G1s.

Parahelice ngankeeae can be discerned from Par. balssi by the male suborbital cristae and G1s. In male Par. ngankeeae , the lateral part of the suborbital crista consists of 1 significantly largest elliptical tubercle and 2–3 elongated or rounded tubercles, which are significantly smaller than the largest elliptical tubercle ( Fig. 2B ) [vs. elongated crest ending with inflated part, followed by 2–4 elongated tubercles, which are larger or equal in size to the inflated part in Par. balssi (K. Sakai et al. 2006: fig. 60; Bouchard et al. 2013: fig. 24D)]; and its male G1 is slender and obviously tapering ( Fig. 2H–M ) [vs. stout and only slightly tapering in Par. balssi (K. Sakai et al. 2006: fig. 70a, b)].

Parahelice ngankeeae can be differentiated from Par. daviei and Par. pilimana by the lateral part of the male suborbital cristae and G1s. The lateral part of the suborbital crista comprises 1 significantly largest elliptical tubercle (without Y-shaped or particularly vertically inflated crest) and 2–3 smaller tubercles in Par. ngankeeae ( Fig. 2B ) [vs. elongated Y-shaped crest and 1–2 smaller tubercles in Par. daviei (K. Sakai et al. 2006: fig. 66a, b; Shih et al. 2020: fig. 2C); and elongated, laterally, particularly vertically inflated crest and 2 smaller tubercles in Par. pilimana (K. Sakai et al. 2006: fig. 65; Shih et al. 2020: fig. 4C)]; and the part near the tip of G1 is relatively stout and only slightly tapering in Par. ngankeeae ( Fig. 2H–M ) [vs. relatively slender and significantly tapering in Par. daviei and Par. pilimana (K. Sakai et al. 2006: figs. 68a–c, 71a–c; Shih et al. 2020: figs. 2E–H, 4C–H)].

Parahelice ngankeeae and Par. pilosa can be separated by the male suborbital cristae. The lateral part of the suborbital cristae in Par. ngankeeae is composed of 1 largest elliptical tubercle and 2–3 tubercles, which are significantly smaller and less convex than the largest elliptical tubercle [vs. crest ending with a slightly inflated part, followed by 2 tubercles, which are only slightly smaller and less convex than (or equal to) the inflated part in Par. pilosa (K. Sakai et al. 2006: fig. 61; Shih et al. 2020: fig. 6C)].

The female Par. ngankeeae is morphologically remarkably similar to Par. balssi , Par. daviei , Par. pilimana , and Par. pilosa , but can be distinguished by the suborbital cristae. In female Par. ngankeeae , the lateral part of the suborbital crista comprises 2 or 3 larger and vertically inflated (significantly larger than the tubercles in the mesial part) and 1 or 2 small, rounded tubercles ( Fig. 2C ) [vs. several isomorphically interspaced tubercles without a significantly larger one in Par. balssi , Par. daviei , Par. pilimana and Par. pilosa ( Shih et al. 2020: figs. 2D, 4D, 6D)].

Figures

FIGURE 1. Parahelice ngankeeae sp. nov. A, B, F, H, male (24.3 × 19.1 mm, holotype, ZRC 2023.0238); C, D, female (15.6 × 12.8 mm, paratype, ZRC 2023.2043); E, G, male (20.0 × 16.2 mm, ZRC 2023.0244). E–H, color in life (courtesy of Heok Hui Tan); A, C, E, F, dorsal view; B, D, ventral view; G, H, frontal view.

FIGURE 2. Parahelice ngankeeae sp. nov. A, B, D, F, H–M, male (24.3 × 19.1 mm, holotype, ZRC 2023.0238); C, E, G, N, female (15.6 × 12.8 mm, paratype, ZRC 2023.2043). A, carapace; B, left male suborbital crista; C, left female suborbital crista; D, outer view of male left cheliped; E, outer view of female left cheliped; F, male pleon; G, female pleon; H–M, male right G1 (H, I, dorsal view; J, K, dorsolateral view; L, M, ventral view); N, right vulva.