Comparison of the morphology and viability of gamma irradiated vegetative cells, wet cysts, and dry cysts of the soil ciliate Colpoda cucullus

Abstract

The soil ciliate, Colpoda cucullus, can tolerate various types of environmental stress, including 4,000 Gy gamma radiation, by forming resting cysts (encystment). In this study, we found that C. cucullus resting cycts also were able to tolerate 8,000 Gy gamma radiation. Irradiated wet cysts and dry cysts were morphologically indistinguishable from nonirradiated cysts and were able to successfully revert to vegetative cells (excystment). The viability (i.e., excystment) of dry cysts was higher than that of wet cysts after 8,000 Gy gamma irradiation. However, vegetative cells did not survive 8,000 Gy gamma radiation and decomposed.