Summary
Host specificity, attachment sites, infection rates and seasonal variation of Dolpos geayi and Argulus juparanaensis were studied a one-year period, from March, 1979, to March, 1980, in the vicinity of Janauacá. a várzea lake in Central Amazonia. Seasonal variation was found to be closely related to water levels, with the maximum infestation peak of D. geayi ocurring during high water (June) and minimum peak during low water (October). D. geayi showed a certain host specificity and was found in four fish species representing three families, namely: one specie of Pimelodidae, one of Erithrinidae and two of Cichlidae. It was not possible to evaluate the host specificity and seasonal variation of a. juparanaensis because the incidence of infestation was too low. Both species were found in the branchial cavities of their hosts.