POPULATION MITOGENOMIC INVESTIGATIONS REVEAL REDUCTION IN GENETIC DIVERSITY IN PEARL SPOT Etroplus suratensis – AN IMPORTANT CANDIDATE SPECIES FOR AQUACULTURE

Etroplus suratensis is one of the most important indigenous Cichlid of the Indian subcontinent with restricted distribution in estuaries of peninsular India and Srilanka. Increasing coastal pollution and climate change contribute to deterioration of their habitats and populations. The adapation potential and intra specific diversity/genetic stock structure of this species were analyzed using partial mitogenomes of 37 fishes (mtDNA 11881bp). Signals of positive and diversifying selection were observed in mitogenomes correlating with habitat characteristics. Habitat specific mutational signals observed have adaptive significance as the populations of the study represented humid tropical climatic zones constituting rainforests in the southwest, semi-arid zones in the southeast and humid subtropical zones in the northeast regions of India demanding genotypic and phenotypic variants with specific metabolic/bioenergetic requirements.

Genetic differentiation was significant            between populations indicating restricted gene flow. Evidence for a recent decline in effective population size during the beginning of Holocene has been observed mainly due to a rise in sea level during the beginning of Holocene in addition to sinking of land connection contributing to shrinking and fragmentation of many coastal habitats. The observed adaptive mitogenome evolution may be the imprints of these geographic events, genetic drift and selective forces of the distinctive ecoregions which form their habitats. Information regarding genetic differentiation and habitat specific substitutions is very valuable for genetic improvement. The reduction in effective population size and genetic diversity driven by habitat fragmentation, pollution, invasive species and over exploitation raises alarm signals for considering its conservation as an immediate priority.