Viaderiana sentus Ng, Dai and Yang, 1997

Sunil, Navami, Unnathpadi, Rajesh & Pullithadathil, Biji, 2023, Five Subtidal Species of the Family Pilumnidae (Crustacea, Decapoda, Brachyura) from the Philippines, with Comparative Notes on Pilumnus hirsutissimus Takeda and Komatsu, 2020, from Japan, Bulletin of the National Museum of Nature and Science. Series A, Zoology 49 (3), pp. 107-122 : 118

Viaderiana sentus Ng, Dai and Yang, 1997

( Figs. 8–9 )

Viaderiana sentus Ng, Dai & Yang, 1997, p. 156 , fig. 6. — Ng, Lin & Ho, 2018, p. 7 , figs. 10–13.

Material examined. Dive site lSecret Gar- denz, Anilao, Batangas, Luzon I., Philippines, 4 m depth, sandy/muddy bottom; 1 Ə (NMCR-92509; cb 8.4 mm, cl 6.4 mm); 30–IX–2018; H. Takakura leg.

Diagnosis. Carapace ( Fig. 8A–B ) rounded quadrate; dorsal surface moderately convex in both directions, smooth, without granules, shallowly divided into regions by indistinct linear furrows; hairs short, soft, regularly cover whole surface, but not disguise areolation; some tufts of longer, club-shaped hairs on frontal, protogastric, branchial regions, a similar tuft of some club-shaped hairs at each lateral end of transverse furrow in front of cardiac region; external orbital angle armed with a sharp, forward-directed spine; infraorbital margin armed with four sharp, equidistant spines along inner part, inner infraorbital angle terminating in a sharp spine; anterolateral margin armed with three sharp spines on conical or weakly bulged bases behind external orbital spine, last spine smaller than others, subequal to external orbital spine. Both chelipeds ( Fig. 9A ) covered with short hairs interspaced with long hairs, some long hairs club-shaped; carpus armed with several distant, dark-colored, curved spines on outer surface, inner angle strongly produced, elongated, tipped with curved, dark-colored spine; palm also armed with sharp, curved, distant spines on outer surface, in smaller chela, spines more prominent than in larger chela. Ambulatory legs ( Fig. 9B–E ) moderately long; each merus armed with one to three sharp spines on anterior margin and a terminal spine; each carpus of all pairs armed anteriorly with a terminal, strong erect spine. G1 ( Fig. 9F, G ) long, not strongly curved, with distal beak comparatively long and sharply pointed at tip.

Color in life. The carapace dorsal surface is dark reddish brown, with some bunds of long feathered, grayish or whitish hairs symmetrically arranged. The chelipeds and ambulatory legs are marked finely with light purplish reticulate patterns.

Remarks. This species was fully described and figured in the original description by Ng et al. (1997), to which the present specimen agrees well in all the respects. Ng et al. (2008) treated the genus Viaderiana to include 17 valid species; among them, V. sentus is characteristic especially in the arrangement of anterior marginal spines of the meri and carpi of the ambulatory legs.

Distribution. Previously recorded from the Nansha Islands in the South China Sea and southern Taiwan ( Ng et al., 1997, 2018). Another Viaderiana species from the Philippines is V. kasei Takeda and Manuel, 2003 , from Bohol, about 150 m depth, in which the ambulatory legs are remarkably long, with the third pair exceeding three times the carapace length.

Figures

Fig. 8. Viaderiana sentus Ng, Dai and Yang, 1Ə (NMCR-92509; cb 8.4×cl 6.4mm). Habitus in dorsal view (A), and carapace, enlarged (B). In Fig. A, the right half of the carapace is denuded, with the horny tip of each anterolateral tooth broken off.

Fig. 9. Viaderiana sentus Ng, Dai and Yang, 1Ə (NMCR-92509; cb 8.4×cl 6.4mm). Right chela in dorsal view (A), right first to fourth ambulatory legs in dorsal view (B–E); left G1 in sternal view (F) and its distal part in abdominal view (G). Scales:A–E=5mm; G=4mm; F=2mm.