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Tilapia Oreochromis spp. are exotic fish introduced in Pakistan from Malaya in 1951. Due to its omnivorous feeding habits and adaptability to harsh environmental conditions, such as salinity and temperature, is considered suitable for aquaculture in Pakistan. However, to date, classification and phylogenetic relationship among the tilapia cultured in Pakistan are poorly understood. In the present study, samples of tilapia were collected from different aquatic systems of Pakistan and Cytochrome c Oxidase subunit I (COI) of mitochondrial genes were investigated to elucidate molecular characterization and find out phylogenetic relationships. DNA extraction was performed from the fin tissue of collected specimens using modified salt extraction method and COI gene of mtDNA was amplified using universal primers for fish and finally the amplified products were sequenced. Sequencing results showed that specimens belonged to species O. mossambicus, of family Cichlidae. Sequence analysis was done by the MEGA 7 software, and cladogram were constructed. The sequence analysis of the genes also showed that there was no significant divergence among all the specimen studied. The species of O. mossambicus was not only confirmed but also separated from other species of family Cichlidae with the help of molecular approach using mtCOI sequence. [ABSTRACT FROM AUTHOR]

We examined the extent of mineral uptake in different tissues of Oreochromis mossambicus from Indus River which is claimed to be polluted by human activities. Samples of water and fish tissues were analysed from two sites (SK = upstream and CH = downstream) of Indus River. Whilst the water quality appeared to be suitable for aquatic life, significant differences between fish tissues and sampling sites were observed for different mineral concentrations. Fins generally had the highest metal load followed by muscles, gills, scales and skin. Na, Mg, Mn and Zn concentrations in different fish tissues were greater for CH than SK, whereas K, Ca, Pb, Cu, Fe, Hg and Cr were higher at SK than CH ( P < 0.001). This variation in metal profiles of different locations of the Indus River was a reflection of relevant mineral pollutions at these sites. It appeared that the pattern of metal uptake in fish tissues can be utilised as an indicator of environmental contamination of river water systems. These studies may help us plan strategies to alleviate the ecotoxicological impacts of heavy metals in freshwaters on fish and human populations. [ABSTRACT FROM AUTHOR]