A preliminary study on the effects of different salinities on some hormones level in serum of Yellow fin seabream Acanthopagrus latus fingerlings.

Abstract

A laboratory experiment was performed on fingerlings of Acanthopagrus latus to estimate the effect of direct transfer from the controlled salinity 1.5 psu to different salinities of (1.5, 7.5, 15, 30 and 45 psu) for periods of (6, 24, 48 and 96) hrs. for short term effect experiments. The following hormones (cortisol, prolactin, thyroxin (T4) and triiodothyronine (T3)) were determined in the serum of these fishes by ELISA technique after exposed to different salinities. Results of T4 and T3 were correlated directly with salinity increase, the (96 hrs.) of time was not enough to reach the stable state of these hormones at all salinities. The salinity 45 psu gave the lowest level of T3 (0.468) ng/ml and showed a sharp drift of T4 level at the time 24 hrs. (0.368) μg/dl, which indicated a breaking down of these hormones, and A. latus fingerlings were unable to sustain at this salinity. Prolactin hormone was correlated inversely with the salinity increase which means that there was ability of this hormone to acclimate in freshwater. Cortisol level was high in high and low salinities indicating its activity in freshwater and seawater environments. The study concludes that the four hormones (cortisol, prolactin, T4 and T3) in the blood serum of A. latus fingerlings showed a clear variations upon salinity changes in the short term effect experiment as a transit status reflecting the capability of these fingerlings to adapt to wide range of salinities vary from 1.5 psu to 30 psu, and the salinity 45 psu was out of its tolerance range.