Pilumnus neglectus Balss, 1933

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 : 113-116

Pilumnus neglectus Balss, 1933

( Figs. 5C , 6 )

Pilumnus neglectus Balss, 1933, p. 25 , fig. 3.

Parapilumnus euryfrons Garth & Kim, 1983, p. 704 , fig. 10.

Pilumnus guinotae Takeda & Miyake, 1968 : Ng, Dai and Yang, 1997, p. 146, fig. 1.

Material examined. Dive site lDive 7000z, Anilao, Batangas, Luzon I., Philippines, 7 m depth, coral reef; 1 Ə (NMCR-92508; cb 8.3 mm including lateral teeth, cl 6.9 mm); 2–X–2018; H. Takakura leg.

Diagnosis. Carapace ( Fig. 6A ) relatively narrow, with tufts of some short and long hairs; dorsal surface ill-defined, without granules; anterolateral margin armed with three spiniform teeth behind sharp external orbital angle; subhepatic region granulated. Ambulatory legs ( Fig. 6A ) unarmed, fringed with long hairs.

Color in life ( Fig. 5C ). The carapace, chelipeds and ambulatory legs are entirely brick red, with darker anterior half of the carapace dorsal surface. The hairs are yellowish brown. In spirit, the colors faded to be entirely creamy yellow.

Remarks. In the revision of the genus Parapilumnus Kossmann, 1877 , Ng (2002) mentioned that Parapilumnus euryfrons Garth and Kim, 1983 , is a junior subjective synonym of Pilumnus neglectus Balss, 1933 , based on examination of the type specimens of both species. The specimen from the Philippines at hand agrees quite well with the line drawing of the carapace by Garth and Kim (1983: fig. 10a), in that the dorsal surface bears scant tufts of short and long hairs mainly on the protogastric and anterior branchial regions ( Fig. 6A ); the three anterolateral teeth are sharp, subequal or the last is slightly smaller than the first two teeth, and curved obliquely forward and directed more outward in the second and third teeth ( Fig. 6A ); the subhepatic region is minutely granulated, and as rightly figured by Garth and Kim (1983), the subhepatic region is visible in dorsal view between the external orbital and first anterolateral teeth. The characteristic movable finger having a longitudinal deep groove throughout the outer surface ( Fig. 6B ) is figured by Balss (1933) and also by Garth and Kim (1983).

The specimens recorded as Pilumnus guinotae Takeda and Miyake, 1968 , from the Nansha Islands in the South China Sea by Ng et al. (1997), is probably misidentified and really referable to P. neglectus . Although the type specimen of P. neglectus was examined by Ng et al. (1997), and the differences of the Nansha specimens from the type specimen are noted as having a more squarish carapace, the external orbital tooth being more acutely triangular and the fin- gers of the chelae are more strongly bent. In spite of the differences mentioned, it is difficult to evaluate the identification to P. guinotae based on the figures of an ovigerous female from three specimens (two ovigerous females and one juvenile). In the specimens from the Nansha Islands, the subdistal edge of the dorsal margin of each ambulatory merus is usually rounded and sometimes weakly angulated, and considered to be a small, low tooth, but in P. guinotae , each merus of the first three ambulatory legs is armed with a small, terminal, not subterminal, tooth, as indicated in the original description of the species by Taleda and Miyake (1968). According to the original description of Parapilumnus euryfrons by Garth and Kim (1983), the ambulatory legs are cited as having no granules and spines.

Distribution. Balss (1933) examined two males from Amboina recorded as P. cursor A. Milne Edwards, 1873 , by De Man (1888), and in addition, probably considerable numbers of the specimens from tropical western Pacific islands (Bougainville Island, the Solomon Islands; New Pomerania Island, the Bismarck Archipelago; Macclesfield Bank in the South China Sea). The record by Garth and Kim (1983) as P. euryfrons was from off southern Luzon, the Philippines, 23 fms depth.

Figures

Fig. 5. Posture in field, with color in life. A: Heteropilumnus planus Ng and Lin, ovig.8 (NMCR-92506; cb 10.9×cl 7.3mm). B: Pilumnus caerulescens A. Milne-Edwards, Ə (NMCR-92507; cb 11.5×cl 14.0mm). C: Pilumnus neglectus Balss, Ə (NMCR-92508; cb 8.3×cl 6.9mm). D: Pilumnus aff. purpureus A. Milne- Edwards, ovig. 8 (NMCR-92510; cb 11.4×cl 7.9 mm).

Fig. 6. Pilumnus neglectus Balss, Ə (NMCR-92508; cb 8.3×cl 6.9mm). Habitus in dorsal view (A), and both chelae in outer view (B).