First zoeal stages of grapsoid crabs (Crustacea: Brachyura) from the East African coast

Abstract

In this study, the larvae of 14 grapsoid species from the East African coast are examined. Original descriptions of the first zoeal stage are provided for the grapsids Grapsus fourmanoiri, G. tenuicrustatus, Pachygrapsus minutus and P. plicatus, and the sesarmids Sarmatium crassum and Sesarma leptosoma. The first zoea of Ilyograpsus paludicola is illustrated for the first time. Redescriptions are presented for the grapsid Metopograpsus messor and the gecarcinid Cardisoma carnifex, while the appendage setation of the varunid Helice leachii, and the sesarmids Chiromantes eulimene, Neosarmatium meinerti, Parasesarma catenata and Perisesarma guttatum are also given and compared with previous work. The first zoeal stages of all these species can be identified, either by comparing their overall morphology or their appendage setation. The validity of combining setation features of the maxilla and maxillipeds to separate grapsoid families is further supported, but special attention is called to the sesarmid Sesarma leptosoma, which presents an unexpected setal arrangement on the basis of the first maxilliped. A more troublesome situation is that of the grapsid Ilyograpsus paludicola. The present descriptions provide evidence of a surprising combination of characters, suggesting that this species should be removed from the Grapsoidea as already indicated by other authors.