Investigation of a parasitic outbreak of Lernaea cyprinacea Linnaeus (Crustacea: Copepoda) in fish from Zimbabwe

Abstract

Infestation of fish by the crustacean ectoparasite Lernaea cyprinacea Linnaeus, 1758 was investigated to establish the extent of infestation, potential effects of the parasite and its ecological adaptations. Fish samples were collected from impoundments in the Malilangwe Wildlife Reserve in the southeastern lowveld of Zimbabwe and these included the cichlids Oreochromis mossambicus, Oreochromis placidus and Tilapia rendalli, the cyprinids Labeo altivelis and Barbus paludinosus, the clariid Clarias gariepinus, the centrarchid Micropterus salmoides and the characid Hydrocynus vittatus. All the cichlids and one cyprinid (L. altivelis) were infested with L. cyprinacea. The two  Oreochromis species exhibited prevalence as high as= 100% and mean intensity up to 149 parasites per fish. Lernaea cyprinacea exhibited an aggregated distribution in host populations and were attached mostly to the ventral and caudal regions of hosts, while the head was the least preferred attachment site. With a few exceptions, there was no significant correlation between parasite prevalence and  intensity with host size, sex, condition factor, gonadosomatic index or fecundity.

Key words: ectoparasite, fish, prevalence, intensity, Malilangwe, Zimbabwe.