Pyloric Ceca Research Articles

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

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.

Observations on an Intestinal Flagellate of Trout

During the spring of 1922 fingerling trout at two of the Bureau of Fisheries hatcheries were found to be badly infected with an intestinal flagellate which was apparently causing serious injury. While the investigation of this parasite is not completed the results obtained are believed to be of sufficient interest to justify the publication of a preliminary paper. The parasite was often present in enormous numbers, in some cases almost the entire contents of the intestine in the infected region being composed of a squirming mass of flagellates. Both brook trout (Salvelinus fontinalis) and rainbow (Salimo shasta) were infected, the infection being somewhat more severe in the latter species. The flagellates were most abundant in the anterior end of the intestine, just behind the stomach in the region of the pyloric ceca. Unless very numerous they were usually found in numbers only in this region but in severe infections occurred throughout the entire length of the intestine. In some cases the flagellates were found in large numbers in the ceca but this condition appears to be exceptional. This parasite was described by Dr. Emmeline Moore under the name Giardia salmonis in a paper read at the 1922 meeting of the American Fisheries Society. Miss Moore has since advised the writer in a private communication that she now believes the flagellate should be assigned to the genus Octomitus rather than Giardia. She has very kindly sent me some of her material for comparison and there can be no doubt that we have both been dealing with the same species.* The parasite is very similar to the one reported by Moroff (1903) from the intestine of rainbow trout under the name Urophagus intestinalis since he believed it to be the species previously described by Dujardin from the intestine of Amphibia. More recently this species has been studied by Schmidt (1920) who also concludes that it is not specifically distinct from the well known amphibian parasite but considers it a subspecies, Octomitus intestinalis truttae. The fact that both the European and American forms occur in the same host species is strong presumptive evidence that they are identical. However, Schmidt's description and figures differ in several essential respects