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Eimeria vilasi (apicomplexa: eimeriidae) from the roundtailed ground squirrel (xerospermophilus tereticaudus).

Between August 2014 and August 2016, 94 (84 adult, 10 juvenile) round-tailed ground squirrels, Xerospermophilus tereticaudus (Helgen et al., 2009), were live-trapped on the grounds of Midwestern University, Glendale, Arizona (33[degrees]39'N, 112[degrees]10'W) and their feces were examined for coccidian parasites. Fecal pellets were collected from traps and handling bags and screened for coccidian oocysts by centrifugal flotation in modified Sheather's solution (Barnard and Upton, 1994). Fecal samples containing oocysts were broken apart in 150-mm petridishes, spread out in a thin layer of 2.0% (w/v) aqueous [K.sub.2][Cr.sub.2][O.sub.7], and kept at room temperature for 3-6 days to allow the oocysts to sporulate; thereafter, the samples were stored at 4[degrees]C. Measurements were taken from 30 oocysts under an oil immersion objective (Duszynski and Wilber, 1997) within 6 wk after they had completed sporulation, and these are reported in micrometers ([micro]m) with means followed by the ranges in parentheses. Oocysts were ~10 d old when photographed. A photo voucher of sporulated oocysts was accessioned into the Harold W. Manter Laboratory of Parasitology, Lincoln, Nebraska (HWML 102965).

Of the 94 round-tailed ground squirrels sampled, 9 (10%) were shedding oocysts of Eimeria vilasi (Dorney, 1962) and 58 (62%) were shedding oocysts of Eimeria callospermophili (Henry, 1932). In addition, 2 of 94 (3%) of the fecal samples contained oocysts of both species.

Sporulated oocysts of Eimeria vilasi (Fig. 1) were ovoidal, 20.1 x 18.1 [micro]m (18 - 25 x 16 - 22), with a length:width ratio of 1.1 (1.1 - 1.2), and a wall that was bilayered, smooth, and 1.0 [micro]m (1.0 - 1.2) thick. One to five (usually one) polar granules were present, and the narrow end of most oocysts contained a small amount of membranous or fibrous material. Sporocysts were ellipsoidal, 10.4 x 6.2 im (8-13 x 5-7), with a length: width ratio of 1.7 (1.3 - 2.2) and a small, translucent Stieda body. The sporocyst residuum was a spheroidal or elongate mass of densely packed granules, and the sporozoites contained a conspicuous posterior refractile body. The oocyst and sporocyst measurements and structural features were consistent with those published for E. vilasi (Dorney, 1962; Wilber et al., 1998; Seville and Patrick, 2001) and its synonyms (see Wilber et al., 1998): Eimeria adaensis (Wilber et al., 1994), Eimeria dorsalis (Hill and Duszynski, 1986), Eimeria morainensis (sensu McAllister et al., 1991), and Eimeria perforoides (sensu Dorney, 1965; Fleming et al., 1979; McQuistion and Wright, 1984).

These findings represent a new host record for E. vilasi. This coccidian has been reported from 12 other species of New World marmotine rodents and has been previously recorded from Arizona and 10 other states as well as from Baja California Norte, Mexico (Hill and Duszynski, 1986; Wilber et al., 1998; Ryan et al., 2001).

Eimeria vilasi was not found in the feces of round-tailed ground squirrels caught during the first field season (August-November 2014); it was only observed in fecal samples collected February-April of both the second (February-August 2015) and third (February-August 2016) field seasons. Similarly, Wilber et al. (1994) reported that the prevalence of E. vilasi peaked in March but declined thereafter in Townsend's ground squirrels, Urocitellus townsendii.

In contrast, E. callospermophili was recovered from the feces of round-tailed ground squirrels captured throughout all months of all three field seasons; the morphological and mensural data for oocysts recovered during the 2014 field season were reported by Hnida (2016). This coccidian has been found in 18 other species of New World marmotine rodents and has been recorded from Arizona, 11 other states, and from locations in Mexico and Canada (Wilber et al., 1998; Hnida, 2016). It has also been reported from seven species of Old World marmotine rodents (Wilber et al., 1998; Golemansky and Koshev, 2007).

In addition to parasitizing a wide range of marmotine hosts across a broad set of geographic locations, both E. callospermophili and E. vilasi tend to occur at relatively high prevalences (Dorney, 1962; Hilton and Mahrt, 1971; Seville et al., 1992; Wilber et al., 1994; Ryan et al., 2001;

Seville and Patrick, 2001). Consequently, it can be predicted that both species of coccidia will be found in other populations of the round-tailed ground squirrel.

This research was conducted under Arizona Game and Fish Department permits and Midwestern University lACUC file no. 2517. We thank M. Elias and L. Jensen for the Spanish translation of the abstract.

Literature Cited

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Submitted 1 July 2016.

Acceptance recommended by Associate Editor, Jerry Cook, 13 September 2016.

John A. Hnida * and Anna Flocken

Department of Microbiology and Immunology, Midwestern University, Glendale, AZ 85308 (JAH) College of Veterinary Medicine, Midwestern University, Glendale, AZ 85308 (AF) * Correspondent: jhnida@midwestern.edu

Caption: Fig. 1--Photomicrographs of sporulated oocysts of Eimeria vilasi. a) Translucent Stieda body (SB) and sporocyst residuum (SR); b) polar granule (PG) and oocyst wall (OW). Scale bars = 10 im. This coccidian was found in 9 of 94 (10%) round-tailed ground squirrels captured in Arizona between August 2014 and August 2016.
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Author:Hnida, John A.; Flocken, Anna
Publication:Southwestern Naturalist
Article Type:Report
Geographic Code:1U300
Date:Dec 1, 2016
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