Opalinata

Classification

Subphylum of Sarcomastigophora.

General Information

These relatively large (up to 1 mm long) protozoa are characterized by numerous close rows of short flagella which move metachronously. Although these flagella look like cilia, the basic organization is quite different. Opalinids have two to numerous identical nuclei; micro- or macronuclei are always absent. Asexual reproduction occurs by longitudinal-oblique binary fission (Figs. 1 and 2); in some species, however, additional sexual fusion stages have been reported. In general the opalinids inhabit the colon or cloaca of amphibians, reptiles, and fish; their pathogenic effects are low; mostly they feed as commensals on intestinal fluids (by pinocytosis). Transmission occurs mainly by oral uptake of cysts (Fig. 1).

Opalinata, Fig. 1

Life cycle of Opalina ranarum. 1 Cysts are excreted by the adult frog and orally ingested by a tadpole. 2 After hatching the young gamont migrates to the cloaca. 3, 4Formation of micro-...