The first-stage zoeas of Carpilius convexus (Forskal, 1775) and Carpilius maculatus (Linnaeus, 1758) (Crustacea : Decapoda : Brachyura : Xanthoidea : Carpiliidae): an example of heterochrony

摘要

The first-stage zoeas of Carpilius convexus (Forskal, 1775) and Carpilius maculatus (Linnaeus, 1758) are described and fully illustrated. Both these Indo-West Pacific species exhibited a unique xanthoidean character for the basis of the second maxilliped, which possesses five (arranged 1,1,1,2) setae instead of the expected four (arranged 1,1,1,1). A comparison with the zoeal stages of Carpilius corallinus (Herbst, 1783) as reported by Laughlin et al. (Laughlin et al., 1983) revealed marked differences including the possession of carapace lateral spines (v. absent in C. convexus only), the subterminal setation of the distal maxillule endopod segment with two subterminal setae (versus one subterminal seta in Indo-West Pacific species), the terminal setation of the distal maxillule endopod segment with four setae (versus three setae in C. convexus only), two lateral spines on the telson (versus three in Indo-West Pacific species) and the number of zoeal stages. The first-stage zoeas of the two Indo-West Pacific species appear to have hatched in a more advanced state of development than those of C. corallinus, and the expression of a number of characters has been accelerated (early onset). In fact, the zoeal stages of both Indo-West Pacific species and carpiliid species appear to be abbreviated because the first zoeas are considered to be equivalent to the third-stage zoeas of C. corallinus.