A Myxosporidian, Myxobolus notemigoni sp. n., Parasite of the Golden Shiner

Abstract

A new species of Myxosporidia (Sporozoa) is described. This parasite occurs in the corium below the scales of the golden shiner, Notemigonus crysoleucas (Mitchill) (Cyprinidae). The name Myxobolus notemigoni sp. n. is suggested and a description of the organism is presented. The parasite is of commercial importance since it detracts from the appearance and market value of its host, an important bait fish. In the course of surveying the diseases and parasites of the golden shiner, one of the principal bait fishes cultured in the United States, the authors encountered an apparently heretofore undescribed myxosporidian. The cysts of the parasite occur under the scales of the host and are readily observed. Among the 30,000 golden shiners which had been harvested from one pond, approximately 20% were infected. Morphology of the spore and the presence of an iodinophilous vacuole place the parasite in the genus Myxobolus. Detailed comparison of data on the present form was made with the published descriptions of North American myxosporidians. Kudo (1920, p. 37) lists ten species of Myxobolus that infect the integument of fishes. Since 1920 approximately 68 new species have been placed in the genus Myxobolus (Kudo, personal communication, 1961). From the literature since 1920 comparisons were made with descriptions given by Bond (1938); Herrick (1936, 1941); Kudo (1929, 1933, 1934); Meglitsch (1937); Nigrelli (1948); Otto and Jahn (1943); Rice and Jahn (1943); and Yasutake and Wood (1957) which include most North American forms. None of these forms have been reported from the golden shiner [Notemnigonus crysoleucas (Mitchill) (Cyprinidae) ]. A limited number infect a similar site in different hosts but are clearly Received for publication 17 December 1963. *This study was sponsored by Southern Illinois University in cooperation with the Illinois Department of Conservation. The assistance of Professor Richard Kudo is gratefully acknowledged. distinguished on the basis of a combination of features including spore size, shape, form and size of cysts, and details of sporogony. The authors consider the present form to be a new species and propose the name Myxobolls notemigoni sp. n. MATERIALS AND METHODS All descriptions are based on parasitized fish obtained from a commercial minnow farm located at Paragould, Arkansas. Live, infected fish were transported to the laboratory and maintained alive throughout the study. Spore dimensions were obtained on both fixed and stained material at a magnification of X 950. Fresh spores were examined in a simple wet mount using a 0.65% NaCl solution. Fixed and stained spores were examined in sections and smear preparations. Heidenhain's iron hematoxylin with an alcoholic eosin counterstain was used for staining both sections and smears. Tissue sections of the body wall of the host were prepared from fish preserved in 10% formalin. Paraffin-embedded tissue was sectioned at 10 to 15 J. The thicker sections were necessary to prevent disruption of the normal relationship between the cyst and the scale of the host. In the description of the organism, special attention is given to spore characteristics since they are the most valuable taxonomic feature (Kudo, 1920). The terminology of orientation and of the structures used to characterize the spores is in accordance with the suggestions set forth and followed by Kudo (1920, and later papers). Description of Myxobolus notemigoni sp. n.