Acclimatization to Heat Stress in Nistari Race of Bombyx mori

Abstract

An experimental study was conducted to analyze thermal sensitivity in multivoltine mulberry silkworm Bombyx mori of Nistari race. Temperature tolerance of the silkworm eggs, larvae, pupae and adults at 17 °C, 33 °C and 43 °C was studied. In general, late stage larvae exhibited maximum tolerance compared to the adult moths and the eggs. Exposure to 17 °C and 33 °C was tolerated equally whereas temperature of 43 °C proved to be lethal. Heat stress resulted in appearance of additional protein species in larval haemolymph. The kinetics of 72 kDa was quite different within and between (IV th and V th instar stage) larval haemolymph after exposure to three different temperatures for 3 consecutive days with 1 hr of duration followed by 24 hr recovery. Increased appearance of 95 kDa protein consequent to heat shock was reported in V th instar larval haemolymph. In Nistari, cocoon and shell weight significantly increased after heat stress over control respectively. This would be due to expression of Hsps at larval stage. These results suggest heat shock protein based breeding strategy for inducing robustness in productive breeds.