Temperature-mediated changes in stress responses, acetylcholinesterase, and immune responses of juvenile olive flounder Paralichthys olivaceus in a bio-floc environment

摘要

We aimed to evaluate stress responses, acetylcholinesterase level, and immune responses of juvenile olive flounder Paralichthys olivaceus in a biofloc environment at different water temperatures. Juvenile P. olivaceus (mean weight 27.96 +/- 3.07 g and mean length 13.4 +/- 1.4 cm) in a biofloc environment were maintained at 20, 22, 24, 26, 28, and 30 degrees C for 2 weeks. The plasma cortisol level in P. olivaceus significantly increased at 28 and 30 degrees C at 1 and 2 weeks, signifying a stress response. The level of heat shock protein 70 (HSP 70) in the liver increased significantly at 28 and 30 degrees C at 1 week, and its level was maintained after 2 weeks at 28 degrees C, but significantly decreased at 30 degrees C. The HSP 70 level in the gills was significantly increased at 30 degrees C after 1 week and at 28 and 30 degrees C after 2 weeks. The level of acetylcholinesterase (AChE) in the liver was significantly inhibited at 30 degrees C after 1 week and at 28 and 30 degrees C after 2 weeks. The AChE level in the gills did not change significantly after 1 week, but was significantly inhibited at temperature > 28 degrees C after 2 weeks. In terms of immune responses, the immunoglobulin M level and lysozyme activity in the plasma significantly decreased at 28 and 30 degrees C after 1 and 2 weeks. The results of the present study indicate that temperatures 28 degrees C or higher induce stress responses, change the neurotransmitter level, and alter immune responses of P. olivaceus maintained in a biofloc environment.