Synonyms: Cytospermium ranae Rivolta, 1878; Coccidium ranae Dobell, 1908.

Type host: Rana temporaria L., 1758, Grass frog.

Other hosts: Pelophylax esculenta (L. 1758), Pool frog.

Type locality: EUROPE: England: Cambridge.

Geographic distribution: EUROPE: England, Germany.

Description of oocyst: Oocyst shape: spheroidal to ovoidal; number of walls: 1; wall thickness: "thin"; wall characteristics: smooth; L x W: 18-22 x 18-22; L/W ratio: 1.0; M: absent; OR: present; OR characteristics: spheroidal mass composed of large granules (line drawing); PG: absent. Distinctive features of oocyst: very thin, single-layered wall that collapses around sporocysts or disintegrates releasing the sporocysts.

Description of sporocysts and sporozoite: Sporocyst shape: spindle-shaped with both ends tapering to a point; L x W: 14 x 7; L/W ratio: 2.0; SB: present as a small nipple-like structure ar 1 end of sporocyst; SSB: absent; PSB: present as a small, nipple-like structure at opposite end of SB; SR: present; SR characteristics: spheroidal body composed of coarse granules between SZ; SZ: longer than sporocyst with their ends curled over one another, with an indistinct N lying in the middle of each. Distinctive features of sporocysts: presence of both a SB and PSB, giving the sporocyst a strong resemblance to those of Monocystis spp.

Prevalence: ~15% of all R. temporaria (Dobell, 1909).

Sporulation: Unknown; however, Dobell (1909) stated that it usually occured in the gut lumen of the lower small intestine and the large intestine (see Remarks).

Prepatent and patent periods: Unknown.

Site of infection: Unknown; however, Dobell (1909) speculated, “It appears most probable that schizogony (= merogony) takes place in the small intestine in the upper part and is completed before any of the parasites proceed to spore formation.”

Endogenous development: Unknown. Dobell (1909) said that he repeatedly examined the intestinal epithelium, the liver, and the kidneys of frogs that were passing “spores” (oocysts and/or sporocysts) and those that were uninfected and never could find any endogenous stages.

Materials deposited:None

Remarks: Dobell (1908, 1909) found this species in R. temporaria near Cambridge and Munich and once in P. esculenta near Munich. He originally named it in 1908, but provided no mensural data and no line drawing, thus creating a species inquirenda. In 1909 he gave a more detailed description, providing both measurements and a line drawing. The most interesting and/or disturbing aspect about his species description is the structure of the sporocysts, which strongly resemble the spores of Monocystis spp. However, Dobell (1909) said that he carefully followed the sporulation process and watched the sporocysts change from what he called “oval” (his Fig. 95) to spindle-shaped (his Figs. 96, 97), with a nipple-like structure on each end. He was clearly aware of the existence of Monocystis spores because he said, “Their resemblance to the spores of Monocystis is often very striking in early stages of development. As I have already noted, these spores are not uncommon in frogs. Of course, when fully formed the octozoic Monocystis spores cannot possibly be mistaken for the dizoic spores of the Eimeria.” If his description is accurate, this is 1 of only 2 amphibian coccidia to possess a PSB (the other being E. spherica from Mesotriton alpestris, from France). The other interesting aspect of Dobell’s (1909) work is that he stated he always encountered sporogony to occur in the lower end of the frog’s gut about the posterior half of the small intestine, together with the large intestine. However, the timeline he gives for sporulation to occur is as follows: unsporulated oocyst to 4 sporoblast stage, 12–20 h; sporoblasts into spores, 20 h; development of the “sporal residuum,” 6–7 h; from the sporal residuum to sporozoite formation, development proceeds more slowly, but no time is given. Thus, sporulation, which he says takes place in the lower small intestine and the large intestine takes, minimally, 38+ h. Our observations on ranid and other anurans maintained in the laboratory indicate that, unless they are fed, they may not defecate for up to a week. Taken together these data suggest that the observation of fully sporulated oocysts in the feces of anurans may not indicate that their development is endogenous and the only way to document endogenous development may be by documenting fully sporulated oocysts in infected host cells. Walton (1949a, b) lists E. ranae as a parasite of P. esculenta (1949a) and R. temporaria (1949b), both from Europe, but provides no other information.