Resting Cysts of the Pigmented Ciliate Blepharisma sinuosum Sawaya, 1940 (Ciliophora: Heterotrichea)

The morphology of Blepharisma sinuosum resting cysts and the dynamics of pigmentation at different stages of encystment are presented for the first time. Cyst morphometrics are similar to other Blepharisma species, with three‐wall layers, bacteria surrounding the ectocyst, a conical plug, and wrinkly surface toward the plug in mature stages. The vegetative moniliform macronucleus changes to a horseshoe shape, and at early stages, the cystic cytoplasm is homogeneously pigmented, comprising a contractile vacuole; later, pigments polarize toward the plug, decorate the cortical layer, and become brownish. This work reinforces the potential role of pigment dynamics on cyst biology.