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Freshwater Crayfish 12(1): 945-946 (1999)

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The post-embryonic development of Cambaroides japonicus and its bearing on crayfish phylogenetics

Scholtz G and Kawai T  e-mail link

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Abstract

The phylogenetic relationships of Eastern-Asian freshwater crayfish of the genus Cambaroides are not settled. They have been placed either with the Astacidae or Cambaridae. To address this question we studied some aspects of the post-embryonic development of the Japanese freshwater crayfish Cambaroides japonicus. After hatching the 1st stage juvenile is attached to the mother by a telson thread. All appendages are present except the first pleopods and the uropods. Setae are absent. The telson is round and equipped with hook-like setae precursors along its margin. The chelae of the first pereiopods are equipped with recurved spines which are used to cling to the mother. During stage 1 the telson thread disappears and the juvenile is only attached to the maternal pleopod setae by those cheliped hooks. After the moult to the 2nd stage the telson bears numerous plumose setae at the margin, and also other setae occur. The cheliped hooks persist and uropods and firsts pleopods are still absent. The 3rd juvenile stage looks more or less like a small adult crayfish. The uropods are present and the cheliped hooks are reduced. The mode of post-embryonic development of C. japonicus highly resembles that of members of the Astacidae rather than that of Cambaridae. This concerns the shape of the telson and the equipment with setae and their precursors, respectively. The juvenile characters are in conflict with adult characters because Cambaroides shares with Cambaridae the presence of an annulus ventralis and the occurrence of cyclic dimorphism. We discuss the consequences of a placement of Cambaroides among the Astacidae or Cambaridae for the general understanding of crayfish phylogeny and evolution.

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Scholtz G and Kawai T. (1999). The post-embryonic development of Cambaroides japonicus and its bearing on crayfish phylogenetics. Freshwater Crayfish 12(1):945-946. doi:

 

 

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