We report the morphological characteristics of oocysts of Eimeria lancasterensisJoseph, 1969, collected from 6 of 6 (100%) eastern gray squirrels, Sciurus carolinensis, collected in Arkansas (n = 3) and Oklahoma (n = 3), and Eimeria ontarioensisLee and Dorney, 1971, recovered from an individual of S. carolinensis from Arkansas. Oocysts of E. lancasterensis were ovoidal to ellipsoidal, measuring (L × W) 24.0 × 14.6 (18–29 × 12–16) µm; shape index (L/W) was 1.6 (1.3–1.8). A micropyle and an oocyst residuum were absent, but up to 2 polar granules were present. Oocysts of E. ontarioensis were piriform and measured 40.6 × 26.0 (37–44 × 23–28); L/W was 1.6 (1.5–1.7). These oocysts possessed a distinct micropyle and rarely a polar granule but lacked an oocyst residuum. The DNA was isolated from both eimerians, and the 18S rDNA genetic markers were PCR-amplified, cloned, sequenced, and analyzed. To our knowledge, this study represents the first time 18S DNA sequence data have been generated from E. lancasterensis and E. ontarioensis found in North American sciurid hosts, as well as new geographic distribution records for these coccidians. In addition, we also include a tabular summary of these 2 species of Eimeria from Sciurus spp. worldwide, with information on their hosts, distribution, and taxonomically important morphological characteristics, including key measurements of oocysts and sporocysts.

我们报告了兰卡斯特艾美耳球虫 ( Eimeria lancasterensis Joseph, 1969) 和安大略艾美耳球虫 (Eimeria ontarioensis Lee ) 卵囊的形态特征，约瑟夫艾美耳球虫 (Eimeria lancasterensis Joseph, 1969) 是从 6 只 (100%) 东部灰松鼠中的 6 只采集的；Sciurus carolinensis是在阿肯色州 (n = 3) 和俄克拉荷马州 (n = 3)采集的1971 年，Dorney 从阿肯色州的S. carolinensis个体中回收。E. lancasterensis的卵囊呈卵形至椭圆形，尺寸（长 × 宽）24.0 × 14.6 (18–29 × 12–16) µm；形状指数 (L/W) 为 1.6 (1.3–1.8)。不存在珠孔和卵囊残留物，但存在最多 2 个极性颗粒。E. ontarioensis的卵囊呈梨状，尺寸为 40.6 × 26.0 (37–44 × 23–28)；长宽比为 1.6 (1.5–1.7)。这些卵囊具有明显的珠孔，很少有极性颗粒，但缺乏卵囊残留物。从两种艾美耳球虫中分离出 DNA，并对18S rDNA 遗传标记进行 PCR 扩增、克隆、测序和分析。据我们所知，这项研究首次从北美松鼠科宿主中发现的E. lancasterensis和E. ontarioensis生成了18S DNA 序列数据，以及这些球虫的新地理分布记录。此外，我们还提供了松鼠属这 2 种艾美耳球虫的表格摘要。全球范围内，提供有关其宿主、分布和重要分类形态特征的信息，包括卵囊和孢子囊的关键测量值。