A TEM study on pre-excystment cellular structures of Euplotes encysticus

Abstract

Right before the excystment of an Euplotes encysticus sawtooth-like folds appeared among the pellicle plasmalemma, the inner and outer alveolar membranes were still sticking together, and were not distinguishable. Microtubular layers already formed at the sites beneath the dorsal cortical pellicle corresponding to vegetative cells, but they still proceed to be organized on the ventral structures. Cristae, highly-tangled with tubular-type structures, appeared on the mitochondria, and were morphologically similar to that of vegetative cells. In the cortical ciliatures, such as ciliary shafts, kinetosomes, surrounding fibrillar cirral baskets, and attached structures of ciliatures, etc., they are different from those in resting cysts which are degenerated or lost. All the ciliature microtubules of ciliary shafts are of the 9+2 pattern, but the microtubule-like structure aggregates at triplet - microtubule centers of many kinetosmes, are still under various stages of differentiation. Microtubules beneath the kinetosomal rows are of a developmentally elongated stage; crowded chromatins of various shapes and sizes are found in macronucleus, but there are no nuclear pores (formed by nuclear membrane as in resting cysts) on the nuclear membrane where these chromatins attached.