Chionoecetes opilio

(Fabricius, 1788)

The carapace including pseudorostrum slightly broader than long, the dorsal surface depressed and covered with flat, rasp-like tubercles on each region. There is a curved row of about 20 spinules along the antero-lateral border extending anteriorly to the antero-external angle of the buccal cavern. The postero-lateral borders are also lined with a curved row of numerous fine spinules, the posterior border almost straight and thickly covered with minute granules. The subhepatic region mounted with several sharp spinules. The pseudorostral lobes are very short and broad, median sinus being narrowly V-shaped. The supraocular eave is markedly convergent anteriorly, between this and the large postocular cup is a small tubercle, which corresponds to the intercalated spine.
The basal segment of antenna distally narrowed and finely serrated along the inner border; having a somewhat prominent subdistal tooth; the flagellum is very short. The infraorbital tooth is broad and serrated, isolated by a wide hiatus from both the postocular cup and the basal segment of antenna.
The arm of chelipeds somewhat compressed, its inner, outer and inferior borders are armed with sharp granules; wrist and palm not compressed, their upper, outer and lower surfaces covered with sharp spinules, which are mostly in longitudinal arrangement. Fingers are longer than the palm, very slender and denticulated throughout their whole length but the movable finger has a broad tooth near the base. Ambulatory legs are compressed, anterior two pairs subequal, third pair a little shorter and the last pair extremely small.
Abdomen of both sexes consist of seven distinct segments.
The female is usually half as large as the male. (Sakai, 1938: 275)

Type locality: Greenland.
Range: west of Greenland (Rathbun, 1925); Labrador - North of Battle Harbour (Rathbun, 1925); Newfoundland (Rathbun, 1925); Nova Scotia (Rathbun, 1925); East coast of Siberia (Rathbun, 1925); Bering Strait and Bering Sea (Rathbun, 1925; Bering Strait (Stimpson, 1907); Sea of Okhotsk (Rathbun, 1925); Kamchatka; Sakhalin (Rathbun, 1925); Japan - Rebun, Kinkazan, Sado, Matsushima, and Oki (Rathbun, 1925), Kinkazan, north-east of Tsushima, north of Mishima, and Noto (Yokoya, 1933), Fukui Prefecture and Kanazawa (Sakai, 1938a), north off Tsushima (Takeda, 1973c), Hokkaido, Sendai, Onahama, Inubo-zaki, and various localities along coast of Sea of Japan (Sakai, 1976a), Yamagata Prefecture (Suzuki S., 1979), Hokkaido (Miyake, 1983), Soya Strait (Takeda & Miyauchi, 1992), Oshoro, Funka Bay, off Kitami, off Hiroo, and Akkeshi (Komai et al., 1992); Korea - east coast of Korea (Rathbun, 1925), Keisho-nando, Kogen-do, Kankyo-nando and Kankyo-hokudo (Kamita, 1941), Chumunjin and Pohang (Kim, 1970), Ju-munjin, Pohang, and Sogcho (Kim, 1973); Arctic Alaska - Point Franklin, Icy Cape, Point Hope, and north of Bering Strait (Rathbun, 1925).

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