Actumnus forficigerus ( Stimpson, 1858 )

Arzivian, Arteen, Alrubaie, Ahmad, Yang, Jessica, Lin, Huiyu, Zhang, Eva & Leong, Rupert, 2022, Crabs (Crustacea, Decapoda) from the Seas of East and Southeast Asia Collected by the RV Hakuhō Maru (KH- 72 - 1 Cruise) 4. South China Sea, Bulletin of the National Museum of Nature and Science. Series A, Zoology 48 (4), pp. 147-191 : 170

Actumnus forficigerus ( Stimpson, 1858)

( Fig. 10C–D )

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 45, 1 Ə (CB 10.0×CL 7.0 mm), NSMT-Cr 30929; 1Ə (6.1× 4.6 mm), 7 ovig.88(6.1× 4.2 mm to 8.6× 6.4 mm), 2 88 (6.4× 4.8 mm; 8.0× 6.1 mm), NSMT-Cr 30930.

Remarks. Takeda and Komatsu (2017) figured the carapace and both chelae of Actumnus forficigerus , which have important features distinguishing this species from its congener. This species is close to A. squamosus (De Haan, 1835) in the general form of the carapace, as being densely covered with short velvety tomentum and sparsely with long silky setae, but differs in the carapace being wider and with the anterolateral margin armed with three stout distinct teeth behind the external orbital angle. Actumnus forficigerus differs remarkably from A. squamosus in having the usual tubercles on the outer surface of the cheliped palm instead of the thick pavement of the tubercles. In the smaller male and all of the females, both chelipeds are stout and covered with some rows of conical granules on the palm outer surfaces, with short and stout fingers, but in the larger male ( Fig. 10C–D ), both fingers are rather elongated and weakly curved downwards against the palm.

Distribution. Hitherto known only from Japanese waters, from Sagami Bay at the Pacific coast of central Honshu to Amami-Oshima Island in the northern Ryukyu Islands, 35–121 m depth ( Sakai, 1939, 1965, 1976; Takeda and Miyake, 1969); now, from the southern South China Sea.

Figures

Fig. 10. A–B: Pilumnus minutus (De Haan), Ə (NSMT-Cr 30937; CB 8.0×CL 6.1mm) from sta. 45. C–D: Actumnus forficigerus (Stimpson), Ə (NSMT-Cr 30929; CB 10.0mm×CL 7.0 mm) from sta. 45. E–F: Actum- nus squamosus (De Haan), 8 (NSMT-Cr 30932; CB 7.7×CL 5.5 mm) from sta. 45.