Morphological and molecular evaluation of Etroplus suratensis (Pices: Cichlidae) from three geographical locations of Peninsular India

Interspecific variations within species is common by having subspecies, races or strains and moreover, population differences are also evident in morphological, molecular, physiological and other characteristics, which will be added up by geographical variations. Etroplus suratensis (Pisces: Perciformes: Cichlidae) is an important brackish water food fish known for its high commercial value and recognised by government as the State fish of Kerala and distributed and cultured throughout the peninsular India. Identification sometimes fails to discriminate species while following the conventional morphometric measures due to phenotypic plasticity and presencs of morphotyes. An attempt was made to differentiate the morphological and molecular characteristics of E. suratensis from three different states, Andhra Pradesh (Visakhapatanam), Karnataka (Mangalore) and Kerala (Cochin) of south India.  Comparison of total of 8 morphometric measurements and phylogenetic evaluation using mitochondrial cytochrome oxidase subunit I (CoI) as molecular genetic marker was used assess geographical variation of the species. Morphologically species from Visakhapatanam showed significant difference from other two localities whereas mean genetic divergence value between E. suratensis collected from Visakhapatnam and Mangalore with a native sample of E. suratensis were found to be significantly low (0.002%), which shows that E. suratensis distributed in Visakhapatnam and Mangalore though they are colour variants, are genetically similar.