Gene Expression Profiling and Physiological Adaptations of Pearl Spot (Etroplus suratensis) under Varying Salinity Conditions

Abstract

AbstractEutroplus suratensis(Pearl spot) is naturally found in estuarine environments and has been noted to have a high salinity tolerance, with the ability to thrive in freshwater as well as seawater. 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 adjustments to changes in salinity, as well as determining their potential to acclimate to a broad range of salinity regimes. Pearl spot fingerlings were placed in tanks with varying salinities (15, 25, 35, 45, 60, and 75ppt) and monitored for mortality at 24-hour intervals up to 120 hours. Results revealed no mortality in the control group (0ppt), as well as in the 15, 25, and 35ppt treatment groups. However, the remaining groups (45, 60, and 75ppt) showed differing levels of mortality, with 44% mortality observed in the 45ppt group and 100% mortality in both the 60 and 75ppt groups. The impact of different salinity levels on the expression of pearl spot genes such as IGF-1, SOD, CAT, NaKATPase, OSTF-1, and HSP70 was investigated, along with a histological examination of the gills. The results showed significant physiological and cellular damage caused by the salinity levels. The expression analysis showed that liver IGF-1 mRNA expression increased by 2.6-fold at 15ppt, and HSP70 mRNA expression in the liver also showed a significant increase with rising salinity levels. In addition, OSTF1 expression exhibited an increase at 15ppt, whereas SOD and CAT expression reached their highest levels at 25ppt. At 15ppt, the expression of NKA mRNA increased significantly by 2.8-fold. The study’s overall findings suggested that the fish demonstrated strong molecular-level performance between 15 to 25ppt salinity levels, with the best results observed at 15ppt. These findings suggest that utilizing a salinity level of 15ppt for Pearl spot production could be viable for profitable aquaculture.