オウギガニ科5種ゾエア幼生の形態

Abstract

Larvae of five species of Japanese xanthid crabs, Medaeops granulosus, Paraxanthias elegans, Novactaea pulchella, Pilumnus vespertilio and P. scabriusculus, were reared in the laboratory from hatching to the last zoea or megalopa stage. They were fed on Artemia salina (L.) nauplii. Their zoeae are described and illustrated in detail, and compared with xanthid crab zoeae in the literature. Under the laboratory conditions, each species has a definite number of zoea stages ; M. granulosus, Paraxanthias elegans and Pilumnus scabriusculus have four zoea stages, Pilumnus vespertilio has three, and N. pulchella has two. The xanthid subfamilies can be classified into eight groups based upon the morphological feature of the antenna II and the setal formulae of endopods of the maxillae I and II of the known xanthid crab zoeae. As a result of these zoeal characters, the genus Halimede appears to have a closer relationship to the subfamily Pilumninae rather than to the subfamily Xanthinae. Furthermore, a key is given to the zoeae of twenty-seven species of xanthid crabs from Japan. The most primitive stock among the xanthid crabs may be xanthinid group including genus Halimede mentioned-above. The ancestral stock provably divided into four lines ; one leading to the Hyperolissa and Zalasinae, one to the Trapeziinae, one to the Pilumninae, and one to the modern Menippinae including the genera Menippe and Sphaerozius.