Temperature Stress on Normal Population and Thermotolerant Population of Procambarus clarkii
All experimental shrimp were acclimatized in experimental net cages at the breeding base for 48 h prior to formal stress exposure, during which the water temperature was maintained at 23 +/- 0.5 degree, dissolved oxygen > 6.0 mg/L, pH 7.2-7.6, and the photoperiod was set at 12L:12D. A total of 300 healthy individuals with uniform size, absence of injury or disease, and not in the molting stage were randomly selected.Temperature stress was induced using a gradual temperature change method, with 23 degree as the starting point. The temperature was increased or decreased at a rate of 1 degree per 4 h until reaching 8 degree or 35 degree, followed by sustained stress for 12 h or 24 h, respectively. During the experiment, continuous aeration was provided, and no feed was supplied to avoid metabolic interference from feeding. A total of six treatment groups were established, with three biological replicates per group. Each replicate consisted of a pooled sample of ventral nerve cord tissues from five shrimp to minimize individual variation.