Type host: Rana arvalis Nilsson, 1842, Moor frog.

Other hosts: None reported to date.

Type locality: EUROPE: Belarus: Vitsyebskaya Voblast, district of Polock.

Geographic distribution: EUROPE: Belarus; Poland.

Description of oocyst: Oocyst shape: ovoidal or spheroidal to subspheroidal; number of walls: 1 (line drawing); wall thickness: not given; wall characteristics: transparent, smooth, and delicate; L x W: spheroidal 23.7 (22-27) or subspheroidal 26 x 22 (23-29 x 20-24); L/W ratio: 1.0 or 1.1; M: absent; OR: absent; PG: absent. Distinctive features of oocyst: none.

Description of sporocysts and sporozoite: Sporocyst shape: ovoidal, slighlty pointed at one end; L x W: 12.6-13.6 x 72-10.8; L/W ratio: not given; SB: absent; SSB: absent; PSB: absent; SR: absent (original description) or present (Kazubski & Grabda-Kazubska, 1973); SR characteristics: a membrane-bound ball of large granules (line drawing), 9-11 x 6-7.; SZ: banana-shaped, 14–15 x 3–3.5 (Kazubski and Grabda-Kazubska (1973). Distinctive features of sporocysts: the membrane-bound SR that is always on 1 side of the sporocyst.

Prevalence: 1 of 38 (<3%) (Kazubski % Grabda-Kazubska, 1973).

Sporulation: Exogenous, but sporulation begins in transit down the intestine and is completed in 24 h at room temperature.

Prepatent and patent periods: Unknown.

Site of infection: Posterior half of the small intestine (Kazubski & Grabda-Kazubska, 1973).

Endogenous development: Unknown.

Materials deposited: None.

Remarks: This species seems most similar to I. brumpti reported from a Pseudepidalea viridis in Syria. However, the oocysts of I. brumpti are longer and, thus, have a larger L/W ratio. Kazubski and Grabda-Kazubska (1973) redescribed I. neos as oval, 21–22 x 19–20 with a delicate wall that bursts after several hours. Their sporocysts were oval or slightly spindle-shaped, 16.2 x 12.8 (15–18.5 x 12–14.5), with a large granular SR (9–11 x 6–7) that was always on one side of the sporocyst and the SZ they measured were banana-shaped, 14–15 x 3–3.5. The main difference between the original description (Yakimoff & Gousseff 1936b) and the redescription by Kazubski and Grabda-Kazubska (1973) was that the latter authors described a large, apparently membrane-bound (line drawing) SR, not reported by Yakimoff and Gousseff (1936b). However, given the same host species and the geographic proximity of the hosts in both descriptions, they suggested that Yakimoff and Gousseff (1936b) simply missed it by saying, “its absence in the sporocysts seems to be hardly probable.” Kazubski and Grabda-Kazubska (1973) also noted that unsporulated oocysts, 17–19 wide, were smaller than sporulated oocysts.