A New Genus and Species of Monorchidae

Abstract

The parasitic fauna of marine fishes from Puget Sound waters is very slightly known and, as a consequence, presents an attractive field for research to anyone interested in parasitology. Since it is further true that knowledge in this phase of zoology for North America as a whole is inadequate and in an unsatisfactory condition, any contribution will be likely to have more than local interest. Linton, among the early writers, has undoubtedly done the most notable work in the field of marine fish trematodes. These works are of value chiefly as a survey of the field and are, therefore, necessarily superficial in many respects. While extensive, in that a large number of forms are described or reported, the descriptions of the species are in many cases incomplete, where not hopelessly inadequate, and the recognition of known forms uncertain. Among more recent works, that of Manter (1926) deals in a most thorough manner with a considerable number of species from a variety of hosts. This paper records the discovery of the occurrence of a new species of trematode belonging to the family Monorchidae Odhner 1911, which family has apparently been previously reported only once from American sources. The parasite was found in the intestine of the common viviparous perch or shiner, Cymatogaster aggregatus Gibbons. The fishes were secured from various localities: Peavine Pass, Davis Bay, False Bay, Squaw Bay, and Deer Harbor, in the San Juan Islands in the vicinity of the Oceanographic Laboratories during the summers of 1930 and 1931. Material was secured by washing out the intestinal contents of the fish, consisting chiefly of amphipods and copepods, and examining it with a binocular dissecting microscope. Nearly 100% infestation was found, only an occasional fish being free of the parasites. The number of trematodes in a single fish varied from one or two to a maximum of twenty one, the average being six or seven. Due to the presence of large numbers of eggs and to the thick, spinous cuticula of the worm, little could be ascertained as to its anatomy in a living condition. Specimens were killed and fixed in hot Bouin's solution, stained and mounted in balsam. The most satisfactory whole mounts were stained in Mayer's paracarmine, while sections were stained as usual in hemotoxylin and eosin.