RECORD OF A MALE SNOW CRAB, CHIONOECETES OPILIO WITH TWO EXTRA FINGERS ON THE LEFT CHELA BY HAJIME MATSUBARA1) Laboratory of Aquatic Genome Science, Department of Aquatic Biology, 196 Yasaka, Abashiri, Hokkaido 099-2493, Japan ABSTRACT Amalesnowcrab(Chionoecetes opilio) with two extra fingers on the left chela was caught from Abashiri, Hokkaido, Japan. These extra fingers arose from the inner proximal portion of the original immovable finger. Morphology of these extra fingers is quite similar to those of the normal fixed finger of the propodus and the dactyl. Previously, such abnormal cheliped has not been recorded in this crab species. INTRODUCTION Naturally occurring abnormal chelae have been reported in the lobsters Homarus americanus (cf. Faxon, 1881; Cole, 1910; Przibram, 1921), Neph- rops norvegicus (cf. Shelton et al., 1981), the crabs Cancer pagurus (cf. Prz- ibram, 1921), Geryon affinis granulatus (cf. Okamoto, 1991), the mud crab Scylla spp. (cf. Fuseya & Watanabe, 1999), the intertidal mud crab Macroph- thalmus japonicus (cf. Suzuki, 1963), the Japanese swimming crab Charybdis japonica (cf. Nakatani & Matsuno, 2004), the hair crab Erimacrus isenbeckii (cf. Suzuki & Odawara, 1971), the crayfish Astacus fluviatilis (cf. Bateson, 1894; Przibram, 1921) and the American crayfish Procambarus clarkii (cf. Nakatani et al., 1992, 1997). Recently, a male snow crab (Chionoecetes opilio) with two extra fingers on the left chela was caught. Such shape has previously not been recorded, and its morphology is herein described. 1) e-mail: [email protected] © Koninklijke Brill NV, Leiden, 2011 New frontiers in crustacean biology: 139-143 140 CRM 015 – Akira Asakura et al. (eds.), NEW FRONTIERS IN CRUSTACEAN BIOLOGY MATERIAL AND METHODS A snow crab with the extra fingers was caught from Abashiri, Hokkaido, Japan (44◦20N 144◦20E, 500 m) on 22 April 2009. The crab was weighed, and the carapace length, carapace width, movable finger length and fixed finger length were measured. RESULTS AND DISCUSSION The carapace length, carapace width and body weight of the specimen are 120.75 mm, 123.26 mm and 676 g, respectively (fig. 1). The two extra fingers arise from the inner proximal portion of the original fixed finger (fig. 2). The length of the normal movable finger (dactyl) is 64.2 mm in the left (fig. 2a-b) and 66.89 mm in the right finger (fig. 2i-j). The length of the normal fixed finger is 50.94 mm in the left (fig. 2c-d) and 53.29 mm in the right finger (fig. 2k-l). In contrast, the extra movable finger (fig. 2e-f) measures 48.85 mm in length and the extra fixed finger (fig. 2g-h) 40.56 mm. Fig. 1. Dorsal view of a male snow crab (Chionoecetes opilio) with an extra chela on the left cheliped. Scale bar: 5 cm..