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Changes in the nuclear phenotypes of OF Diatoms infestans klug, induged by thermal shocks^*

Marly M. Dantas^I,II; Maria Luiza S. Mello^I

^IDepartamento de Biologia Celular, Instituto de Biologia, UNICAMP, 13081 Campinas, SP, Brasil. Send correspondence to M.L.S.M.
^IIPresent address: Departamento de Biologia, Universidade Federal de Sergipe, 49000 Aracaju, SE, Brasil

ABSTRACT

The nuclear phenotypes of Malpighian tubule epithelial cells of 4th instar nymphs of Triatoma infestans Klug were subjected to thermal shocks at 0°C and 40°C for one and 12 hours and were analyzed just after the stress, and three and 30 days later. In addition to the phenotypes usually described for control specimens, pyknotic, giant and vacuolized nuclei, as well as nuclei exhibiting an apparent unravelling of chromocenter chromatin were detected in the test specimens. The decrease in number of cell nuclei, which occurred at shorter or longer intervals after the thermal shocks, were assumed to have been caused not only by degeneration of the cells bearing vacuolized and pyknotic nuclei, but also by nuclear fusion. It was assumed that the giant nuclei, which appeared predominantly in the specimens subjected to the hyperthermal shock, and the presence of hsp, played a role in the insect's unchanged survival under this specific experimental condition. Although many of the nuclear characteristics found in the specimens subjected to thermal shock have also been observed with other stress agents, the heat shock was much more effective in eliciting the apparent chromocenter heterochromatin unravelling response in T. infestans. Based on the types and frequencies of nuclei observed after the hypothermal shock and on the drop in insect survival caused by this treatment, it seems that, if cryoprotectors are present in T. infestans, they are not efficient enough to protect the insect from a relatively prolonged hypothermal shock.

Keywords: Nuclear phenotypes; Thermal shocks.

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* Part of a thesis presented by M.M.D. to the Instituto de Biologia, UNICAMP, Campinas, in partial fulfillment of the requirements for the Masters degree.