A New Myxosporidan in Red and Golden Shiners

Abstract

Myxosoma cyprini sp. n. is described in the gills of the red shiner, Notropis lutrensis, and golden shiner, Notemigonus crysoleucas, from Oklahoma. Cysts measuring 0.3 ua or less occur adjacent to capillary endothelial cells of secondary gill lamellae. Infected fish were collected in October 1971 and in June 1972. M. cyprini is disporoblastic and development is asynchronous. Mature spores are pyriform in front view and lenticular when viewed from the side. Fresh spores average 14.4 A in length by 8.0 uL in width by 7.5 u in thickness. Polar capsules are pyriform and 7.1 u long by 3.0 u wide. Approximately 9 windings of the polar filaments are seen inside each capsule. Extruded polar filaments are 100 to 110 A long. Mucous envelopes are present. All of the 35 red shiners and 9 of 10 golden shiners contained M. cyprini. Host reactive cells do not appear at the locus of the parasite. A new species of Myxosoma was found in the branchial tissues of two cyprinoid fishes, the red shiner, Notropis lutrensis, and the golden shiner, Notemigonus crysoleucas. Immature and mature stages of the parasite are described herein. The specific name M. cyprini, referring to the hosts' family name, is proposed. MATERIALS AND METHODS Twenty-two red shiners were collected by seining Little Stillwater Creek, Payne County, Oklahoma, on 2 October 1971. Thirteen more red shiners and 10 golden shiners were collected from the same site on 8 June 1972. Portions of infected gills were macerated in water on glass slides or were fixed for 4 to 16 hr in a cold 2% glutaraldehyde solution containing 0.5% acrolein, 4.0 mM calcium chloride, and buffered by 0.2 M sodium cacodylate to pH 7.4. Fixed tissues containing the parasite were washed in cold 0.22 M sucrose in the cacodylate buffer and either examined as squashed preparations with phase contrast (Zeiss system) or embedded for sectioning. The embedding steps included postfixation for 30 min in 2% Os04 in the cacodylate buffer, dehydration in a graded ethanol series, and infiltration in Spurr's low-viscosity medium (hard formula; Polysciences, Industrial Park, Warren, Pennsylvania). The embedment was polymerized at 37 to 40 C for 4 hr and 64 to 70 C for 6 to 7 hr. Sections, 1 /t thick, were cut with glass knives on a Porter-Blum MT-2 ultramicrotome, mounted on glass slides, and stained on a hot plate with 0.5% toluidine blue in 1% sodium borate. Stained sections were rinsed in running water, air-dried, flooded with immersion oil, and cover-slipped. Observations of stained sections were made by both bright-field and phasecontrast optics using 125 to 2,500X magnification. Mucous envelopes were demonstrated in fresh spores by the method of Lom and Vavra (1963). Received for publication 18 July 1973. Description of the sporogenic stages and spores is based on composite findings in both fresh and fixed unstained smears. Description of the plasmodium and of its spatial relationship to host tissues is based on observations of sectioned and