Salinity, Temperature and Ammonia Acute Stress Response in Seabream (Sparus aurata) Juveniles: A Multidisciplinary Study

Abstract

The present study aimed to investigate the acute response of gilthead seabream (<i>Sparus aurata</i>) juveniles exposed to temperature, salinity and ammonia stress. Radioimmunoassay was used to evaluate cortisol levels, whereas insulin-like growth factors (<i>igf1</i> and <i>igf2</i>), myostatin (<i>mstn</i>), heat-shock protein 70 (<i>hsp70</i>) and glucocorticoid receptor (<i>gr</i>) gene expression was assessed trough Real-Time PCR. The presence and localization of IGF-I and HSP70 were investigated by immunohistochemistry. In all the stress conditions, a significant increase in cortisol levels was observed reaching higher values in the thermic and chemical stress groups. Regarding fish growth markers, <i>igf1</i> gene expression was significantly higher only in fish subjected to heat shock stress while, at 60 min, <i>igf2</i> gene expression was significantly lower in all the stressed groups. Temperature and ammonia changes resulted in a higher <i>mstn</i> gene expression. Molecular analyses on stress response evidenced a time dependent increase in <i>hsp70</i> gene expression, that was significantly higher at 60 min in fish exposed to heat shock and chemical stress. Furthermore, the same experimental groups were characterized by a significantly higher <i>gr</i> gene expression respect to the control one. Immunostaining for IGF-I and HSP70 antibodies was observed in skin, gills, liver, and digestive system of gilthead seabream juveniles.