Increasing levels of salinity in coastal and freshwater environments as a result of rise in sea level is linked to climate change and it impacts fish growth adversely. Etroplus suratensis (Pearlspot) is the largest species among the indigenous cichlid which is essentially brackishwater fish that has become naturally acclimated to freshwater. Understanding the basis of tolerance and acclimatization to increased environmental salinity and freshwater condition can help the regional aqua-farmers to mitigate predicted impacts of climate change in that region. Technically the last decade contributed many methodologies to understand the salinity adaptation mechanisms; suppression subtractive hybridization (SSH) library generation being one of them. In this study we performed SSH technique to identify genes involved in salinity adaptation and osmoregulation in gills of E. suratensis, generating from fishes exposed to seawater (SW-36 ‰) as compared to freshwater (FW-0 ‰). Here, SSH was used to identify alterations in gene transcription of E. suratensis after exposure to 36‰. A random 105 clones were selected and sanger sequenced from the subtractive c-DNA libraries which gave a total of 80 gene fragment sequences. Sequencing analysis and homology searches showed that these EST’s represented 68 unique gene and 12 duplicates. Of the 68 unique genes, 62 shared high homology with fish genes of known functions including immunity, stress, cellular process, cytoskeleton and transporter. Gene expression profile of the selected 10 EST’s acclimated to SW and FW conditions from SSH library was carried out. The candidate genes identified in E. suratensis gills provided valuable information to study and understand new functional genes that act as osmosensors in osmotic regulations.

Euryhaline, salinity tolerance, SSH, c-DNA library, gene expression profile