Eimeria brevoortiana, a New Sporozoan Parasite from Menhaden (Brevoortia tyrannus), with Observations on Its Life History

Abstract

Most of the species of the genus Eimeria are intestinal parasites throughout their life histories. In a few instances o6cysts have been found in various other organs of the host animal, such as kidney, spleen, liver, air bladder and testis. With the exception of one, Eimeria stiedae (Lindemann), which is parasitic in the liver of rabbits, the life histories of these species are incompletely known. Any information, therefore, which helps explain their peculiar behavior will no doubt be of value in determining the relationships of other members of the genus and of the genus itself. During the course of an investigation of the parasites of marine fishes, o6cysts of an eimerian parasite were found in the testes of menhaden. Two parasites of this nature have previously been described from the testes of fishes, E. sardinae (Thelohan, 1890) from sardines, and E. nishin Fujita (1934) from herring. In these cases, as with the present species, the only stages seen in the testes were those that belonged to the sporogonic cycle, zygotes, sporocysts, and sporozoites. Since the typical life history of an eimerian includes a schizogonic as well as a sporogonic cycle, a study was begun to determine the location of the former in menhaden. Smears and sections of testes, stomach, pyloric ceca, intestine, spleen, liver and kidney were examined. Eventually, structures resembling the schizogonic stages of other eimerians were found in the epithelium of the pyloric ceca-spores, schizonts, macroand microgametocytes. Together with the cycle of sporogony in the testes they form a complete life history of an eimerian, which is described in the following pages. The writer is indebted to many friends for help during the course of the work, particularly to Dr. A. S. Pearse of Duke University, under whose direction it was carried out. Dr. H. F. Prytherch kindly extended the facilities of the United States Fish and Wildlife Service Laboratory at Beaufort, North Carolina. Capt. Chas. Hatsell and many fishermen of Beaufort helped in collecting material, and Margaret Hardcastle aided the writer greatly in the examination of much of it. Dr. D. C. Boughton of the United States Bureau of Animal Industry read the manuscript and made many helpful suggestions.