Effect of temperatures on growth, yields and heat shock protein expression of Eri Silkworm (Samia ricini D.)

Abstract

The effect of high temperatures on the growth, yields and heat shock protein (HSP) production of eri silkworm (Samia ricini D.) was carried out by exposure the 5th instar day 3 larvae to different temperatures, 36±1, 40±1, 42±1, 45±1 and 48±1°C for 3 hours, compared to control treatment by rearing eri silkworm continuously at normal temperature (25±2°C, 80±5%R.H.). After treated with high temperature condition, the eri silkworm larvae were reared at 25±2°C, 80±5%R.H.until cocooning, pupation, adult stage, coupling and laying eggs. The result exhibited that survival rates, cocooning rate and almost yields varied inversely to temperatures especially between 42±1 – 48±1°C. At the highest temperature, survivals and yields were the lowest, while those values were the maximum nearly all control treatments. At 48±1°C treatment, the means of all parameters were the lowest; larva survival (50.00%), survival of larva – adult (38.33%) and cocooning rate (41.67%), which were significantly different to other treatments(P<0.05). Other yields affected by 48±1°C were also the lowest; fresh cocoon weight(2.5078 g), pupa weight (2.1508 g), shell weight (0.3429 g), total cocoon shell weight(2.88 g), fresh cocoon weight/10,000 larvae (10.47 kg), egg laying/moth (287.56 eggs), hatchability (72.67%), total egg laying (1,121.33 eggs) and total hatchability (800.11 eggs). Detection of HSP of 5th instar larvae day 3 of eri silkworm treated with 5 different temperatures (36±1, 40±1, 42±1, 45±1 and 48±1 °C) was performed using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE), compared to control treatment (25±2°C; 80±5%R.H.). The result was clearly that the eri silkworm treated with all high temperatures expressed HSP bands of approximate 50 kDa. Whereas HSP band was not detectable in control treatment. The HSP is applicable in the thermotolerant variety improvement program of eri silkworm.