Combined stress of acute cold exposure and waterless duration at low temperature induces mortality of shrimp Litopenaeus vannamei through injuring antioxidative and immunological response in hepatopancreas tissue.

Abstract

High mortality is a frequent occurrence during live transport of shrimp species and the biochemical mechanism remains unknown. This study aimed to explore the influence of combined stress of acute cold exposure (AC) and waterless duration (WD) on survivability and biochemical response of shrimp L. vannamei during live transport. The shrimps in NC and AC groups remained the total survivability throughout the experiment while the shrimps exposed to AC+WD stress exhibited significantly higher mortality since 6h afterwards (P<0.05) and the median survival time was calculated at 10.46h. Moreover, the typical combined stress points at AC+WD3h, AC+WD6h and AC+WD9h were assigned for exploring the immunological and antioxidative responses. For immunity response, the total hemocyte counts (THC) decreased with the prolongation of duration time and the activities of non-specific immunity enzymes such as phenol oxidase (PO), acid phosphatase (ACP), alkaline phosphatase (AKP), aspartate aminotransferase (AST) and alanine transaminase (ALT) were significantly elevated in AC+WD9h groups (P<0.05). Moreover, compared with that in NC group, the significant accumulation of reactive oxygen species (ROS) was observed in AC group and then reduced in combined stress groups (P<0.05), with the highest level of malonaldehyde (MDA) in AC and AC+WD3h groups. Overall, the significant elevation of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and total antioxidant capacity (T-AOC) was detected in AC+WD9h group (P<0.05). Furthermore, the accumulative pathological impairment on hepatopancreas tissue revealed the cytoskeleton degradation. In addition, correlation analyses visualized the correlation between oxidative stress and biochemical response. This study not only deepens our understanding on the biochemical mechanism of shrimp mortality induced by combined stress, but also provides a potential strategy for improving the management of L. vannamei during live transport.