The trematode parasites of marine mammals

The internal parasites of marine mammals have not been extensively studied, although a fairly large number of species have been described. In attempting to identify the trematodes in the United States National Museum helminthological collection from mammals of the orders Cetacea, Pinnipedia, and Sirenia, it was necessary to review the greater part of the literature dealing with this group of parasitic worms. This review showed that there is not in existence a single comprehensive paper on the trematodes or other parasites of these mammals. Many of the descriptions of species have appeared in publications having a more or less limited circulation and are unavailable except to those having access to the larger libraries. This survey showed, moreover, that of these parasites, very little is known of the incidence of infestation, distribution, or injurious effects upon their respective hosts. Furthermore, not a single life history is completely known for any of the species which may be regarded as normal parasites of these animals. In view of the paucity of information on the trematodes from these groups of mammals, the writer has undertaken to assemble descriptions of all species reported as parasites of these hosts, with the hope that such a paper may serve a useful purpose in aiding other workers in determining specimens at their disposal, and to stimulate them to redescribe such of the species as are incompletely known. In addition to this compilation, three new species, one of which represents a new genus, are described, and additions made to the existing descriptions of several species. Unless stated to the contrary, the. compiled descriptions have been taken from the original publications. For the sake of uniformity all measurements, when less than one millimeter, have been expressed in microns.