Changes in physiological and biochemical indexes of Procambarus clarkii during simulated air transport

【Objective】To identify the key environmental factors affecting Procambarus clarkii survival during air transportation and to provide the scientific basis for targeted pre- and post-transport treatments to improve survival rates.【Method】The conditions of air transportation were simulated by placing the crayfish in foam boxes under ice-cold conditions with(perforated group) or without(sealed group) ventilation. Real-time monitoring of oxygen content, temperature and relative humidity in the foam box was performed during simulated air transportation. After 18 h of simulation, the serum, hepatopancreas, gill filament and midgut samples were collected and the serum activities of lysozyme, polyphenol oxidase(PPO), superoxide dismutase(SOD) and malondialdehyde(MDA) were determined. Hepatopancreas SOD activity, total antioxidant capacity(T-AOC), MDA content, protein carbonyl content and gill filament Na⁺ K⁺ -ATPASE activity were used, together with paraffin sections of the hepatopancreas, gill filaments and midgut, to calculate the survival rate of P. clarkii after simulated air transport.【Result】During simulated air transport, the relative humidity was not obviously altered, while the changes in temperature and oxygen content were significantly affected and observed to cause stress reactions in P. clarkii. After the simulation, the activities of lysozyme, PPO and MDA in the serum of the sealed group were significantly increased(P<0.05, the same below), while the activities of SOD were significantly decreased. Hepatopancreas protein carbonyl content, MDA content and T-AOC level were significantly higher than those in the perforated and control groups, while SOD activity showed no significant change. The activity of Na⁺K⁺-ATP in gill filaments of both the sealed and perforated groups was significantly higher than that of the control group. After simulated air transport for 18 h, the cray-fish survival rate was higher. However, the survival rate of both the sealing and perforated group decreased significantly from the 4^th day, and only 59.33% of the sealed group was alive on the 7^th day. Most of the respiratory epithelial cells were exfoliated and necrotic, and the branchial membrane structure was destroyed.【Conclusion】The changes of temperature and oxygen content are the main environmental factors affecting the survival rate of P. clarkii during air transportation. The simulated air transport caused serious and irreversible damage to P. clarkii and a large number of P. clarkii died after their return to control conditions. Therefore, the survival rate of air-transported P. clarkii can be improved by feeding immune enhancers before transportation or optimizing the environmental conditions following transport to improve recovery rates.