Structure of the oocysts and excystation processes of four Eimeria spp. (Protozoa: Eimeriidae) from the Colorado pika, Ochotona princeps.

Oocysts of Eimeria banffensis Lepp, Todd, and Samuel, 1972, Eimeria cryptobarretti sp. n., Eimeria princepsis sp. n., and Eimeria calentinei sp. n. are described from the Colorado pika, Ochotona princeps, collected from 3 mountain sites in Colorado. Subspherical oocysts of E. banffensis measure 23 to 34 by 18 to 25 p (mean 27.6 by 23.0 p ) with ovoid sporocysts 10 to 16 by 7 to 10 p (mean 12.5 by 8.5 p ) . A micropyle, oocyst residuum, and polar granule are absent, but a sporocyst residuum, Stieda body, and substiedal body are present. The ellipsoidal oocysts of E. cryptobarretti measure 24 to 35 by 18 to 22 p (mean 29.8 by 20.6 p ) with distinct, elongate bulb-shaped sporocysts 13 to 18 by 7 to 11 p (mean 15.2 by 8.4 p ) . A micropyle, sporocyst residuum, and Stieda body are present, but a polar granule and oocyst residuum are absent. Ellipsoidal oocysts of E. princepsis measure 19 to 24 by 15 to 19 p (mean 21.5 by 17.3 p ) with ovoid sporocysts 10 to 14 by 5 to 8 p (mean 12.3 by 7.3 p ) . A micropyle, polar granule, sporocyst residuum, and Stieda body are present, but an oocyst residuum is absent. Ovoid oocysts of E. calentinei measure 26 to 32 by 18 to 23 p (mean 28.5 by 20.0 p ) with ovoid sporocysts 10 to 14 by 6 to 9 p (mean 12.0 by 7.4 p) . A polar granule is absent, but a micropyle, oocyst and sporocyst residuum, and Stieda body are present. The in vitro excystation of sporozoites of E , cryptobarretti and E , calentinei is described. Sporozoites of E. banffensis and E , princepsis did not excyst after exposure to the excysting fluid for 60 min. Possible reasons for this are discussed. The first report of coccidia of pikas (OchoRESULTS AND DISCUSSION tona princeps) from North America was by Eimeria banffensis Lepp, Todd, and Samuel, 1972 Barrett and Worley (1970) in Montana, but (Figs. 1-3) they did not describe oocysts. Recently, Lepp Description et al. (1972a, b ) and Duszynski and Brunson Oocysts subspherical (Fig. 1 ) ; oocyst wall of (1972) described oocysts from pikas in Canuniform thickness, about 2, consisting of 2 layers: ada and Colorado, respectively. outer layer green, > 1, finely pitted (Fig. 2 ) ; inner layer yellow, < 1, smooth (Fig. 2 ) ; microDuring July and August 1970, 30 pikas pyle, oocyst residuum, and polar granule absent; were collected from three mountain sites in sporulated oocysts ( n = 100, 15 to 35 from each two counties in Colorado. The localities of of 4 host specimens) 23 to 34 by 18 to 25 (27.6 the hosts varied from 11,000 to 13,200 ft by 23.0), with shape indices 1.04 to 1.36 (1.20); sporocysts ovoid, 10 to 16 by 7 to 10 (12.5 by above sea level. Intestinal contents from each 8.5), with shape indices 1.22 to 1.70 (1.46); host were examined for coccidia and four Stieda body present with closely apposed subspecies of Eimeria were observed. One of the stiedal body (Fig. 3 ) ; sporocyst residuum granEimeria, E. banffensis, was recently described ular, in a diffused band between sporozoites (Fig. (Lepp et al., 1972b) and additional data on 3 ) ; structure of sporozoites in intact sporocysts difficult to distinguish. its structure are presented. The other three Host: Ochotona princeps; Larimer and Clear Eimeria species are described as new. Creek counties, Colorado. Location in host: Unknown. Oocysts recovered MATERIALS AND METHODS from contents of small and large intestines. Preoalence: Present in 7 of 30 pikas examined. All techniques involved in collecting and proThese included 5 of 14 hosts collected on Mt. cessing fecal material, measuring, studying, and Evans (elev. 12,800 to 13,200 f t ) and 1 of 4 crushing oocysts, and excysting sporozoites were collected on Goliath Peak (elev. 11,600 to 12,000 previously reported (Duszynski and Brunson, f t ) , both in Clear Creek County and 1 of 12 col1972). Measurements are in microns with the lected from Crown Point (elev. 11,000 to 11,500 means given in parentheses following the ranges. f t ) in Larimer County. Sporulation t ime: Most oocysts were completely Received for publication 13 April 1972. sporulated after 72 hr at 30 C. Duszynski & Brunson in Journal of Parasitology (1973) 59. Copyright 1973, American Society of Parasitologists. Used by permission.