Coccidia from kangaroo rats (Dipodomys spp.) in the western United States, Baja California, and northern Mexico with descriptions of Eimeria merriami sp. n. and Isospora sp.

Since January 1975, 104 of 361 (29%) kangaroo rats (Dipodomys spp.) examined for Coccidia had oocysts in their feces. These included 32 of 71 (45%) D. agilis from California (3 of 8, 38%) and Baja California Norte (29 of 63, 46%); none of 18 D. deserti from Sonora, Mexico; one of one D. gravipes from Baja Norte; 43 of 124 (35%) D. merriami from California (1 of 4, 25%), New Mexico (16 of 49, 33%), Baja Norte (12 of 23, 52%), Baja Sur (6 of 20, 30%), and Sonora, Mexico (8 of 28, 29%); 17 of 103 (17%) D. ordii from Oregon (0 of 9), Texas (3 of 9, 33%), and New Mexico (14 of 85, 17%); three of 14 (21%) D. panamintinus from California; and eight of 30 (27%) D. spectabilis from New Mexico. The following coccidians were identified from infected rats: Eimeria balphae, E. chobotari, E. scholtysecki, Eimeria sp., E. utahensis, and Isospora sp. from D. agilis; E. scholtysecki from D. gravipes; E. balphae, E. chobotari, E. chihuahuaensis, E. dipodomysis, Eimeria merriami sp. n., Eimeria sp., and E. utahensis from D. merriami; E. balphae, E. chobotari, and E. dipodomysis from D. ordii; E. scholtysecki and Eimeria sp. from D. panamintinus; and E. balphae and E. scholtysecki from D. spectabilis. Sporulated oocysts of Eimeria merriami sp. n. from D. merriami were subspherical, 24.3 X 22.7 (21-27 X 20-26) gm with ovoid sporocysts 10.6 X 7.6 (9-12 X 7-9) ,m. No micropyle or polar body were present, but oocyst and sporocyst residua, Stieda and substieda bodies were present. The oocyst wall has two layers. Sporulated oocysts of Isospora sp. from D. agilis were nearly spherical, 25.5 X 25 (21-28 X 20-28) ,um with broadly ovoid sporocysts 14.5 X 10.0 (12-19 X 9-13) Mm. No micropyle, oocyst residuum and substieda body were present, but a polar granule, sporocyst residuum and Stieda body were present. The oocyst wall had two layers. There are no other isosporans described from heteromyid rodents. Greater than 91% (195 of 213) of all Dipodomys found to be naturally infected with Coccidia in this study, and in all other published surveys, harbored only a single parasite species at any one time. We examined eight species of Dipodomys from California, New Mexico, Oregon, Baja California (Norte and Sur), and Sonora, Mexico, and found them to be infected with seven eimerians and one isosporan. One of the eimerians, found in two specimens of D. merriami, is described here as new. Oocysts of an isosporan were also found in one specimen of D. agilis, but because only a few oocysts were available for study we decline to name it at this time. MATERIALS AND METHODS All hosts were killed in the field a few hr after being live trapped. The abdominal cavity was opened, the intestinal tract removed, and the cecum and colon were slit lengthwise and preserved, with their contents, in vials containing 2.5% aqueous (w/v) K2Cr207. Upon return to the laboratory, vials were refrigerated (4 C) until they could be processed and examined. Processing for oocysts consisted of separating fecal contents from cecal/colon tissue, filtering, incubating and examining by coverslip flotation as described elsewhere (Duszynski et al., 1982). Oocysts were measured with an ocular micrometer and photographed with either Panatomic-X or Ilford Pan F 35 mm film within a Received 11 January 1982; revised 9 June 1982; accepted 15 June 1982. Zeiss Universal Photomicroscope equipped with both brightfield (Neofluar) and Nomarski-interference 100X objectives. All measurements are in ,um with the ranges in parentheses following the means.