Gene expression profiling and physiological adaptations of pearl spot (Etroplus suratensis) under varying salinity conditions

Eutroplus suratensis (Pearl spot) is naturally found in estuarine environments and has been noted to have a high salinity tolerance. By examining the impact of various salinity levels on the growth and survival of pearl spot, the present study aims to enhance aquaculture profitability by assessing their adaptability and physiological ad-justments to changes in salinity and determining their potential to acclimate to a broad range of salinity regimes. Results revealed no mortality in the control group (0 ppt), and in 15, 25 and 35 ppt treatment groups. However, the remaining groups (45, 60, and 75 ppt) showed differing levels of mortality with 44 % mortality observed in the 45 ppt group and 100 % mortality in both the 60 and 75 ppt groups. The expression analysis showed that liver IGF-1 mRNA expression increased by 2.6-fold at 15 ppt, and HSP70 mRNA expression in the liver also showed a significant increase with rising salinity levels. In addition, OSTF1 expression exhibited an increase at 15 ppt, whereas SOD and CAT expression reached their highest levels at 25 ppt. At 15 ppt, the expression of NKA mRNA increased significantly by 2.8-fold. The study's overall findings suggested that utilizing a salinity level of 15 ppt for pearl spot production could be viable for profitable aquaculture.