RESUMO
In the present study, the effect of temperature shock (sudden and gradual) by increasing water temperature from 28 °C to 40 °C on survival, behavioral responses and immunological changes in Litopenaeus vannamei (L. vannamei) was studied. In sudden temperature shock, experimental groups were maintained at different temperature ranges such as 28 °C- 31 °C; 28 °C-34 °C; 28 °C-37 °C and 28 °C-40 °C along with 28 °C as control. For gradual temperature shock experiments, the initial water temperature was maintained at 28 °C for 24 h in control and then increased to 1 °C for every 24 h until reaching 40 °C. On reaching the final temperature of 40 °C, it was kept stable for 120 h. Results indicated that the increasing water temperature (sudden shock) affected survival, behavioral responses and immunological parameter. No shrimp survived at 40 °C treatment (sudden), whereas in the gradual temperature shock experiment 20% of animals survived at 40 °C. The increasing water temperature had no effects on behavioral responses up to 37 °C (gradual), but at 40 °C the observation of muscle cramps, low swimming rate, no feeding, muscle and hepatopancreas color turned whitish. Overall, the results suggest that L. vannamei can tolerate water temperature up to 34 °C under sudden shock and 37 °C under gradual shock conditions. This study reveals that shrimp L. vannamei can self-regulate to a certain extent of temperature variation in the environment.
