Pilumnus orbitospinis Rathbun, 1911

Zou, Wenjun, Jiang, Qin, Wang, Yanling, Wei, Wenbin, Sun, Xiaodong, Basu, Karen, Chen, Qiuyu, Kotecha, Aachal, Li, Sijing, Liu, Ruyuan, Patel, Vaibhavi & Chen, Youxin, 2024, One New and Two Rare Species of the Genus Pilumnus Leach, 1816 (Crustacea: Decapoda: Brachyura: Pilumnidae) from Takase Submarine Bank off the Izu Islands, South of Tokyo, Japan, Bulletin of the National Museum of Nature and Science. Series A, Zoology (Philadelphia, Pa.) 50 (4), pp. 145-153 : 151-152

Pilumnus orbitospinis Rathbun, 1911

( Fig. 4B )

Pilumnus orbitospinis Rathbun, 1911, p. 229 , pl. 16 figs. 14–15. — Parisi, 1916, p. 185. — Sakai, 1939, p. 536, pl. 100 fig. 6; 1965, p. 158 (English part), p. 68 (Japanese part), pl. 78 fig. 3; 1976, pp. 484 (in key), 487, fig. 261a (English vol.), p. 300 (Japanese vol.). — Takeda & Miyake, 1968, pp. 6 (in key), 19, figs. 4d–f, pl. 3 fig. B. —Takeda et al., 2005, p. 112. — Takeda & Ueshima, 2006, p. 92.

Material examined. Takase submarine bank, northwest off Nii-jima I., Izu Is., 140–180 m depth, 1 ovig.8 (cb 8.9×cl 7.2 mm), NSMT-Cr 6659; 9-VII-1968, dredged by the TV Umitaka Maru of Tokyo University of Fisheries (now, Tokyo University of Marine Science and Technology ) and donated by T. Okutani .

Remarks. The ovigerous female examined agrees with the original description and the records from Japanese waters cited above, in having the convex and ill-defined carapace covered with the rather sparse longish hairs and four sharp anterolateral spines including one at the external orbital angle, and each ambulatory merus armed with one or two spinules on the anterior margin and a terminal spine. The most obvious characteristic of P. orbitospinis is the presence of a remarkable spine at the inner angle of the infraorbital margin ( Fig. 4B ). In the present female, the carapace anterolateral spines are much shorter than those of the male figured by Takeda and Miyake (1968, pl. 3 fig. B), indicat- ing one of the sexual intraspecific differences.

Distribution. This species was originally described on the basis of two females (one ovigerous) from the Chagos Archipelago in the central Indian Ocean, 108–216 m depth, and is otherwise known from Sagami Bay and Tosa Bay, the Pacific coast of Japanese mainland, 85–200 m depth, Izu-Oshima Island, Izu Islands, 160–180 m depth, and southwest of Kume-jima Island and about 100 km west of Okinawa-jima Island in the central Ryukyu Islands, 372–375 m depth. Now, from Takase submarine bank, northwest off Nii-jima Island, Izu Islands, 140–180 m depth.

Figures

Fig. 4. A: Pilumnus curvipenis Komai and Motoh, ovig.8 (NSMT-Cr 11052; cb 5.8×cl 3.8mm). B: Pilumnus orbitospinis Rathbun, ovig.8 (NSMT-Cr 6659; cb 8.9×cl 7.2mm).