Eimeria crotalviridis sp. n. from prairie rattlesnakes, Crotalus viridis viridis, in New Mexico with data on excystation of sporozoites and ultrastructure of the oocyst wall.

Oocysts of Eimeria crotalviridis sp. n. are described from praire rattlesnakes, Crotalus viridis viridis in New Mexico on the basis of light and electron microscopy and in vitro excystation of sporozoites. Sporulated oocysts of E. crotalviridis are elliptical, 26.4 X 22.3 (23-29 X 20-24) micrometer with ovoid sporocysts 11.7 X 8.1 (11-13 X 7-9) micromiter. A micropyle, micropyle cap and polar bodies are absent, but oocyst and sporocyst residua and Stieda and substieda bodies are present. Excysted sporozoites are 12.4 X 2.8 (11-13 X 2-3) micromiter and have 1 large posterior refractile body and a nucleus with a prominent nucleolus. Ultrastructurally, the oocyst wall has 2 layers, a thick, electron-dense, highly sculptured outer layer composed of a fine granular matrix and a thin, granular, osmiophilic inner layer, separated from the outer layer by at least one unit membrane. These layers are 441 (353-510) and 21.6 (19-29) nm thick, respectively. Within 15 min after exposure to a trypsin-sodium taurocholate fluid, sporozoites of E. crotalviridis excysted from 5-month-old sporocysts.