Polyploid mosaics induced by temperature shocks in the giant freshwater prawns Macrobrachium rosenbergii

Abstract

Cold shocks at 10°C, 12°C, 15°C and heat shocks at 32°C, 35°C or 38°C were administered to 4 h- or 6 h-fertilized eggs of the giant freshwater prawns, Macrobrachium rosenbergii, for a period of 4 h or 6 h. The treated eggs were further cultured in vitro at room temperature (29°C). The control was in vitro cultured at room temperature to hatching. Both cold and heat shocks caused an abnormal chromosome separation resulting in a formation of fused nuclei. Mosaics, individuals containing both diploid and polyploid cells, rather than complete polyploids were induced. Cold shocks at 10°C were detrimental while at 15°C were inefficient. Whereas application of 12°C to 4 h-fertilized eggs for 6 h or to 6 h-fertilized eggs for 4 h produced polyploid mosaics and enlarged embryos but caused great reduction in the survival rates. Heat shocks at 32°C did not induce mosaicism or enlarged embryo, while at 38°C were detrimental. Application of 35°C to 4 h-fertilized eggs for a long duration of 6 h or to 6 h-fertilized eggs for 4 h produced some mosaics and enlarged embryos. Though, enlarged embryos appeared to develop normally and survived to the hatching days (18-19 days), none engaged in hatching. Defect in the hatching enzymes upon the treatments was suggested.