Chaunus Wagler 1828

Duszynski, Donald W., Bolek, Matthew G. & Upton, Steve J., 2007, Coccidia (Apicomplexa: Eimeriidae) of amphibians of the world, Zootaxa 1667 (1667), pp. 1-77 : 22-23

Host genus Chaunus Wagler 1828

(44 spp.)

Eimeria bufomarini Paperna and Lainson 1995 ( Fig. 3)

Type host: Chaunus marinus (L. 1758), Cane toad.

Other hosts: None reported to date.

Type locality: SOUTH AMERICA: Brazil, Pará State, Island of Marajo, Salvaterra .

Geographic distribution: SOUTH AMERICA: Brazil: Pará State, Island of Marajo.

Description of sporulated oocyst: Oocyst shape: spheroidal to subspheroidal; number of walls: 1; wall thickness: unknown; wall characteristics: colorless and very delicate; L x W: 9.2 x 9.0 (9–10 x 9–10); L/W ratio: 1.0 (1.0–1.1); M, OR, PG: all absent. Distinctive features of oocyst: colorless, fragile wall.

Description of sporocyst and sporozoites: Sporocyst shape: ellipsoidal; L x W: 6.3 x 3.7 (6–7 x 4); L/W ratio: 1.7 (1.6–1.7); SB: almost imperceptible, knob-like; SSB and PSB: absent; SR: present; SR characteristics: irregular mass of small and large globules that fills much of the sporocyst; SZ: mostly obscured by SR, but 2 RB detected by TEM. Distinctive features of sporocyst: massive SR that obscures the SZs.

Prevalence: 5 of 17 (29%) in Salvaterra, 1 of 13 (8%) in Belém, Pará.

Sporulation: Endogenous, oocysts sporulate within epithelial cells and usually mature sporocysts, but rarely intact oocysts, are discharged into the gut lumen.

Prepatent and patent periods: Unknown.

Site of infection: Epithelial cells of the intestine.

Endogenous stages: Both merogony and gamogony occur in the tips of epithelial cells just below the brush border. Developing meronts, microgamonts and undivided parasites were difficult to distinguish from one another. Two different dividing stages were seen: 1) with pale blue cytoplasm (Giemsa-stained), had up to 11 N when 4.2 in diameter, 26 N when 8.4 in diameter, and 36 N when about 10.5 x 10 wide; and 2) with a more darkly staining cytoplasm with 6–8 N and measuring 8–15 x 7. Two types of mature meronts were seen: 1) produced 15 long, thin merozoites, 5.6–8.4 x 1.0–1.4, and 2) produced only up to 8 merozoites, which were stouter, 7.0 x 2.1. Early developing macrogamonts had a large, pale N with a distinct nucleolus and were 4–5 x 3 in smears. Developing microgamonts were not found in smears, but in tissue sections mature forms were 7 x 8, with up to 10 microgametes. Zygotes in tissue sections were subspheroidal, 7.5 x 5.0. Unsporulated oocysts in smears were subspheroidal, 10.5 x 8.0, but rounded up to 10 x 10 when sporulated.

Ultrastructural study of meronts showed that, at first, merozoites shared their common parasitophorous vacuole (PV), but that as they matured each became separated into an individual, adjoining vacuole. Some merozoites divided prior to the formation of the next generation of meronts, presumably by endodyogeny. Thus, merozoites with their own pellicle and subcellular organelles (micronemes, rhoptries, etc.) were found together in the same PV with stages that had differentiated into the next generation of juvenile meronts within their own limiting membrane. Both juvenile and dividing meronts, and gamonts, contained food vacuoles (?) and electron-dense globules that sometimes occupied the width of the parasite. Differentiation of merozoites was by exogenesis.

Ultrastructurally, developing microgamonts have peripherally arranged N, adjoined to centrioles and a mitochondrion. Their cytoplasm contains a Golgi complex and an ER network, and mature stages are filled with amylopectin granules. Macrogamonts gradually accumulate amylopectin granules as they mature and their cytoplasm also contains large food vacuoles, scattered and aggregated ribosomes, a network of rough ER, mitochondria, Golgi-like aggregates and Type I wall-forming bodies. Young oocysts (zygotes) are filled with large amylopectin granules, some lipid vacuoles and the remains of electron-dense bodies first seen in macrogamonts. No sign of a rigid oocyst wall is found either in young oocysts or in mature oocysts containing sporocysts with developed SZ. After sporulation, a second, delicate membrane appeared below the limiting membrane (wall?) of the oocyst, which lies in close contact with the PV wall. SZ each have 2 RB and the bulky SR contains many amylopectin granules.

Pathology: No evidence of pathology was found in any of the infected hosts.

Materials deposited: Tissue sections of intestine are deposited in the Museum National dHistoire Naturelle, Paris (303LN). Other sections and intestinal smears are in the Department of Parasitology, Instituto Evandro Chagas, Belém, Pará, Brazil and in the Department of Animal Sciences, Faculty of Agriculture, Rehovot, Israel.

Remarks: The oocysts of E. bufomarini are similar in size to those of E. laminata ( Fig. 5) and E. himalayani ( Fig. 4, below), both of which are described from 2 bufonids in the genus Duttaphrynus in India, but Paperna and Lainson (1995) considered conspecificity unlikely due to geographic and host species differences, a concept with which we agree.