Summary
Host specificity, attachment sites, infestation rates and seasonal, variation of Argulus multicolor and Argulus pestifer were studied during a one-year period, from March, 1979, to March, 1980, in the vicinity of Janauacá, a lake "várzea" in Central Amazônia. Seasonal variation was found to be closely related to water levels, with the maximum infestation peak of A. multicolor ocurring during high water (June & July) and the minimum peak during low water (November). A pestifer showed a pattern of seasonal variation inverse to that of the other species studied, with the maximum infestation peak ocurring during low water (November & December), and the minimum peak during hight water (June & July). A. multicolor showed a certain host specificity and was found in four fish species representing two families namely: two species of Cichlidae and two of Serrasalmidae. A. pestifer showed high host specificity and was found to parasitize one genus, Pseudoplatystoma and two species P. tigrinum and P. fasciatum. A. multicolor was found parasitizing the branchial and buccal cavities while A. pestifer was found on the sternal surface of their respective hosts.