Critical thermal minima of Penaeus semisulcatus (Decapoda: Penaeidae) acclimated to four temperature levels

Critical thermal minima (CTmin) and lower incipient lethal temperature (LILT) were determined for Penaeus semisulcatus juveniles at four different acclimation temperatures (14, 20, 26, and 32 Q. The effect of cooling rate on the CTmin was also investigated. The CTmin of shrimps at these respective acclimation temperatures were 7.1, 8.9, 10.5, 12.6 C and 6.6, 8.0, 9.7, 11.4 C and 6.1, 7.2, 8.3, 9.9 C for the cooling rates of 0.25, 0.5, and 1.0 C/h, respectively. The LILT value of P semisulcatus were 5.23, 6.14, 7.36, 8.57 C at 14, 20, 26, and 32 C, respectively. The results indicated that both the cooling rate and the acclimation temperature significantly affected the CTmin (P < 0.05). Acclimation temperature had also significant effects on the LILT of P. semisulcatus (P < 0.05). In acclimation temperatures between 14 and 32 C, the acclimation response ratio values were 0.30, 0.26, and 0.21 at the cooling rates of 0.25, 0.5, and 1 C/h, respectively. The cold tolerance zone in which P semisulcatus can survive for short period in this study ranged from 6.1 to 12.6 C.