著者

杉田 博昭 関口 晃一 宍倉 文夫 山道 祥郎

出版者

日本動物分類学会

雑誌

動物分類学会誌 (ISSN:02870223)

巻号頁・発行日

no.22, pp.1-6, 1982-05-25

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The four extant horseshoe crabs are morphologically so similar to fossil specimens of the genus Mesolimulus that one has referred to them as "living fossils". The recent horseshoe crabs are assigned to two subfamilies, that is, Limulinae and Tachypleinae. The Limulinae includes only one American species, Limulus polyphemus and the Tachypleinae includes three Asian species, Tachypleus tridentatus, T. gigas and Carcinoscorpius rotundicauda. The hybridization experiments revealed that the fertilization could not be accomplished between Limulus and Asian species gametes, while three Asian horseshoe crabs were cross-fertilizable one another. Developmental capacity of hybridized eggs among the three Asian species was not equivalent, suggesting that one had rather not assign three Asian horseshoe crabs to such two diverse genera as Tachypleus and Carcinoscorpius in the current taxonomy. These results are in concord with the idea that American and Asian horseshoe crabs diverged from a common European ancestor (or separate ancestral species) and that the three extant Asian horseshoe crabs diverged from a common Asian ancestor.