Alterations Due to Heat Shock in Biological and Commercial Features of the Silkworm, Bombyx mori

Abstract

The impact of HS on larval growth and development, ERR, cocoon characteristics and biochemical elements of carbohydrate content was investigated using FC2 X FC1 bivoltine hybrid silkworm breed. On the third day of the fifth instar, the FC2 X FC1 bivoltine hybrid was treated to HS at 30, 35, 40 and 45ºC for 1 h with 1 h retrieval. Following that, silkworms were maintained in the rearing house under naturally fluctuating environmental circumstances in order to assess their intrinsic potentiality for overcoming temperature changes and producing cocoons in contrast to non-HS B. mori larvae. At 40°C, the biological and commercial features gained the most weight. As a result, although all larvae heat shocked at 35 and 40°C metamorphosed into pupae with better growth than controls, the fifth instar showed the greatest improvement in it. However, heat shock temperature of 45˚C was lethal since all the biological and commercial characters were severely affected in all instars. Thus, temperatures of 40°C should be considered when screening for better parents to develop thermotolerant breeds/hybrids for tropical countries such as India, in order to elicit a profound response and acquire tolerance to overcome the fluctuated environmental condition. Both control and HS showed a sequential increase in carbohydrate content but found declined upon HS of 45˚C.