Energy response of swimming crab Portunus trituberculatus to thermal variation: Implication for crab transport method

• Energy produce capability is reduced in P. trituberculatus subject to thermal variation or aerial exposure.
• Aerial exposure leads to more energy demand and consequently a more severe disturbance of energy status.
• The transport of P. trituberculatus without water seems to be a better alternative at lower temperature.

Temperature variation and air exposure are two predominant abiotic stressors during the transport and storage of Portunus trituberculatus. To understand the effects of these factors on P. trituberculatus, we examined the hemolymph (hemocyanin, glucose and lactate level) and muscle indicators (glycogen content, metabolic enzymes activity and energy status) through laboratory experiments. Energy status was evaluated by measuring changes in total adenine nucleotide (TAN) concentration, ATP, ADP, AMP, ADP/ATP, AMPATP, adenylate energy charge value (AEC) and the apparent equilibrium constant for adenylate kinase (K′ADEN). It was found that thermal variation significantly influenced (P < 0.05) the energy metabolism of crabs by increasing lactate level, ADP and AMP content, cytochrome c oxidase (CCO) and lactate dehydrogenase (LDH) activity and the ratio of ADP/ATP and AMP/ATP and by decreasing glucose and ATP content, AEC and K′ADEN value at high temperature. At lower temperature, all parameters except the hemocyanin and lactate level were similar between immersed and aerial exposed crabs (P > 0.05), indicating that the maintenance of energy homeostasis was independent of environment media. However, at higher temperature, air exposure resulted in more perturbation of energy metabolism in the crabs compared to immersion, as a greater decrease in hemocyanin, ATP, AEC and K′ADEN level (P < 0.05), and a greater increase in glucose, ADP, AMP, ADP/ATP and AMP/ATP level (P < 0.05) were observed in aerial exposed crabs. In summary, high temperature especially during air exposure could lead to a severe stress in P. trituberculatus, and the perturbation of energy status as a result of mismatch between energy demand and supply is a possible inducer of crab death.