An ultrastructural study on the merogonic stages of Goussia senegalensis (Faye, 1988) Diouf and Toguebaye, 1993 (Apicomplexa, Coccidia) from the liver of Pagellus bellottii (Pisces, Teleostei)

Little is known about the merogony of coccidians from fishes in Africa. To our knowledge, including both freshwater and marine fishes, developmental stages have been recorded for only Goussia cichlidarum, Cryptosporidium sp. parasitizing the stomachs of juvenile cichlid fish, and Eimeria (s. l.) vanasi. A survey of coccidians parasitizing marine fishes from the coast of Senegal (West Africa) was done between 1988 and 1992 and samples of infected organs were collected for further transmission electron microscopy observations. Merogonic stages were observed. Goussia senegalensis undergoes merogony in the hepatic cells of Pagellus bellottii as follows: meronts develop inside the cytoplasm of the hepatocytes and merozoites develop from them through endodyogeny and endopolygeny. Early meronts are uninucleate, but for most advanced meronts the single large nucleus is divided into 2 or more nuclei as the pellicle precursors of new merozoites arise. In this study, those associated with invaginations of the inner membrane were then arranged around portions of the cytoplasm, each including one nucleus. Mature meronts contained either 2 or several merozoites. At least 2 generations of merozoites developed.