Stage-related profiles of the reactions of cells to heat shock during meiotic prophase inParamecium caudatum

Abstract

The first meiotic prophase in the conjugation of Paramecium caudatum is a lengthy process, during which the morphological changes of micronuclei can be classified into five stages. In this experiment, mating pairs were placed at 35°C for 1 h at each of the five stages and nuclear changes were observed by staining with Carbol fuchsin solution. In cells treated in stage II, all processes of conjugation were inhibited and each cell maintained one micronucleus and one macronucleus. When the heat treatment was applied at stage III or IV, multimicronucleate cells were often induced. Heat treatment at stage III disturbed all aspects of nuclear differentiation, including macronuclear fragmentation and formation of new macronuclear anlagen. However, in cells treated at stage IV, such nuclear events were not disturbed. These results showed that the effects of heat shock at each stage are quite different and they suggest that the meiotic prophase plays an important key role in the subsequent nuclear events of conjugation in terms of nuclear differentiation, macronuclear fragmentation and development of macronuclear anlagen. © 1996 Wiley-Liss, Inc.