Eimeria os Crouch & Becker, 1931.

Type host: Marmota bobac

Other hosts: M. baibacina; M. caudata; M. menzbieri; M. monax; M. sibirica.

Other names: Eimeria callospermophili; E. giganteos; E. monacis.

Type locality: North America: USA, Iowa, Near Ames.

Other localities: Asia: Buriatia; Kazakhstan.

Description of oocyst: Oocyst shape: ovoid; wall thickness: not given; layers: 1 (in drawing); outer layer colour: clear to pale yellow; outer layer texture: smooth; micropyle: present; micropyle width: not given; MC: absent; OR: absent; PG: absent; size: 20-26 x 18-22; L/W ratio: not given. Distinctive features of the oocyst: o÷cyst "endomembrane" sometimes protrudes through the micropyle and looks like a bubble.

Description of sporocysts and sporozoites: Sporocyst shape: ellipsoid; size: 9-13 x 5-8; SB: present; SB L x W: not given; SB characteristics: small, dark (in drawing); SSB: absent; PSB: absent; SR: present; SR characteristics: rounded or irregularly biconvex, lying either to the side or between the SP; SR size: not given; SP: not described. Distinctive features of sporocyst: none.

Remarks: Eimeria os was described from M. monax by Crouch & Becker (1931). In 1941, Machulsky described E. os from M. siberica, but the oocysts he described lacked a micropyle, a feature of E. os, and his description more closely matches E. callospermophili. Svanbaev (1963) described a species as E. os, but Levine & Ivens (1965) thought it was E. monacis (see E. monacis remarks). In 1965, Dorney described and photographed what he called E. os from M. monax, but the size was much larger and, thus, we named Dorney's (1965) species, E. giganteos. Fleming et al. (1979) and McQuistion & Wright (1984) reported E. os from M. monax, but they followed the description in Dorney (1965); thus, it is likely they actually saw E. giganteos.

References: Crouch & Becker (1931); Dorney (1965); Fleming et al. (1979); Levine & Ivens (1965); McQuistion & Wright (1984); Machulsky (1941, 1949); Nukerbaeva & Abenov (1979); Svanbaev (1963); Svanbaev & Rachmatullina (1971).