Effect of unfavourable enviromental factors on alga-containing and
alga-free Climacostomum virens
Karajan B. and Raikov I.
Institute of Cytology, RAS, Tikhorezki av. 4, St. Petersburg, Russia
Cells of ”green” clone of C. virens and an obtained experimentally alga-free clone were compared for two their responses: towards a 1h pulse of temperature stress (4 and 36-40°C), and food limitations. The temperature resistance to cold and heat was found to depends on the stage of cell cycle rather than on the presence or absence of algal symbionts. The early dividing stage (D1) was more sensitive to the temperature stress than stages G1 and S. In both investigated clones the cells divided normally when temperature shock was given at the late dividing stage (D2). In both clones the temperature stress causes a significant lengthening of the cell cycle independent of the stage of the cell cycle. The ”green” cells are more resistant to high temperature (sublethal temperature for ”green” cells is 40°C, for algae-free cells 37-38°C).
It has been shown that food limitation may cause in both the compared clones several alterations commonly associated with apoptosis in metazoan cells. Ciliate cells subject to ”apoptosis” for 10-12 days remain motile, but do not feed and are reduced in size. Electron micrographs show chromatin condensation and nuclear lamina disassembly. Cytoplasmic organelles are preserved. At the final stages the apoptotic cells may be phagocyted by normal neighbouring cells, or die. It is to be noted that alga-containing cells were more resistant to food limitation.
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