Oregonia mutsuensis YOKOYA, 1928,as a Synonym of O. gracilis DANA, 1851

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  • <国立科博専報>ムツケセンガニについて

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Abstract

The genus Oregonia has been considered to comprise three species. They are 1) O. gracilis DANA, 1851,ranging from the Bering Sea southward to Monterey Bay along the North American coast and also southward to the Boso Peninsula along the Pacific coast of Japan and to the Yellow Sea coasts through the Sea of Japan, 2) O. bifurca RATHBUN, 1902,known from the Aleutian Islands and the Bering Sea, and 3) O. mutsuensis YOKOYA, 1928,recorded from some localities in Mutsu Bay and off northeastern Honshu, Japan. A close examination of a long series of specimens referable to Oregonia in the collection of the National Science Museum, Tokyo, suggests O. mutsuensis should be regarded as a young form of O. gracilis, which shows remarkable individual, sexual and developmental variations. The original description of O. mutsuensis is not sufficient for depicting its specific characters; short and divergent rostrum, rather smooth dorsal surface of the carapace, and triangular terminal segment of the male abdomen have been the features regarded by its author as being peculiar to his new species. According to the present study, however, all these features are characteristic of the young or juvenile individuals of O. gracilis smaller than about 1cm in the carapace length. The slender chelipeds of the type male of O. mutsuensis, 7.7mm in the length of carapace, shown in the original illustration, is also indicative of this fact. Its type specimens are not extant, so that it is safely considered to be a synonym of O. gracilis. Another representative of the genus, O. bifurca, known from north of Rat Island in the Aleutian Islands and Bowers Bank in the Bering Sea, is rare, but well established thanks to the important contributions of its original author and GARTH (1958). In the National Science Museum, Tokyo, there is a male from the sea far north of Midway Island at the latitude of 35°N. This species is characterized by having short divergent rostral spines and much wider carapace. This record has extended its geographical range considerably southward in the North Pacific.

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  • CRID
    1570854176973408384
  • NII Article ID
    110004313086
  • NII Book ID
    AN00379635
  • ISSN
    00824755
  • Text Lang
    ja
  • Data Source
    • CiNii Articles

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