Abstract
Ovigerous females of Cymo melanodactylus, C. andreossyi and C. quadrilobatus were collected from a coral reef, Jeddah (Biadah, Obhur) and Thuwal, Saudi Arabia and reared in the laboratory. The morphological features of the zoea I of C. andreossyi, and zoeae I and II of C. quadrilobatus, as well as the complete larval stages of C. melanodactylus, have been described for the first time. Some characters distinguish these species: cephalothorax size; ratio of the length of antennal protopod and exopod; setations of the endopod of second maxilliped and the presence of a small tooth on the basal endite of the maxillule in the zoea I of C. melanodactylus and C. andreossyi. Morphological features of cephalothorax spines, setations of the endopod of antenna, first and second maxillipeds and the inner spines of telson change as the larval stages of C. melanodactylus progress. The morphological features of the zoeal and megalopal stages of the above-mentioned crabs were compared with those of the larvae of some conspecifics and other xanthid larvae described from the Red Sea. The megalopa of C. melanodactylus can easily be differentiated from those of Chlorodiella nigra and Leptodius exaratus by the setations of the exopod and endopod of antennule, antenna, maxillule and first to third maxillipeds.