Larval Stages of Cardiodectes sp. (Caligoida: Lernaeoceriformes), a Copepod Parasitic on Fishes

Five postembryonic stages of a fish copepod belonging to the genus Cardiodectes Wilson were recovered from pelagic snails, Janthina globosa Swainson, in the West Indies. They are probably identical with those found in Creseis sp., with those reported in Janthina exigua Lamarck in the Mediterranean Sea, and with those recently collected from Janthina janthina (L.) in Madagascar. A comparison with adult metamorphosed females of Cardiodectes medusaeus (Wilson) and Peroderma cylindricum Heller reveals that these larvae belong to Cardiodectes, a genus characterized by having only three pairs of functional swimming legs and two labial flaps encircling the mouth tube. The five stages of development are: free-swimming copepodid, chalimus I, chalimus II, chalimus III, and free-swimming adult form. Each stage is separated by one molt. Sexual dimorphism is not observable until chalimus II.