This study is a preliminary investigation on the use of laser scanning confocal fluorescence microscopy as a tool for examining cytological changes and subsequent mitotic processes when Penaeus indicus eggs are submitted to heat-shock treatments. Antibodies to tubulin and in some cases to DNA were applied to fixed eggs after the removal of hatching envelope. Changes on microtubule containing structures and the expected suppression of the first cleavage have been observed at intervals from fertilization to early embryonic stages. Great differences have been noted between control and treated eggs during early events but they became less apparent in later ones. The pronuclear migration was sensitive to the microtubule-depolymerizing heat-shock but amphimixy was unaffected. Under the best conditions, it was noticed that even if heat-shock inhibited or retarded cytokinesis, it had no effect on centrosome duplication. At the time of the second cleavage, some of the uncleaved eggs divided directly into four cells as a consequence of the presence of four centrosomes, some divided into three and some having one division-delayed were at a two-cell stage. Further cell divisions proceeded normally in appearance in the above-mentioned four cleaved eggs. Frequently, the two-cell stage embryos showed, as in the controls, centrosomes equally distributed among each blastomere, while only one of them contained a nucleus. Despite the atypical suppression of first cleavage, the new information obtained permit us to draw conclusion concerning the time of application of heat-shock and provides a preliminary report for developing a reliable and efficient tetraploidizing treatment in shrimps and crustaceans.