Variations among <scp>Nile</scp> tilapia reproductive strains: An integrative morphometric and molecular approach

The rapid expansion of tilapia aquaculture highlights the importance of assessing the variations between the local and improved strains to ensure sustainable production. The present study conducted an integrative analysis of morphometric traits, reproductive performance, growth and reproduction-related gene expressions in three commercially important tilapia strains such as Nile tilapia (Oreochromis niloticus), genetically improved farmed tilapia (GIFT) (Oreochromis niloticus strain) and red tilapia (Oreochromis niloticus × Oreochromis mossambicus) to measure their genetic and phenotypic variations. From each species, 100 samples were collected from the farm and used for this study. Evaluations included morphometric measurements, organo-somatic indices, fecundity, egg characteristics and transcriptional profiling of key genes. GIFT and red tilapia exhibited superior morphometric traits, including higher body weight, total length and body depth compared to Nile tilapia. GIFT showed the highest gonadosomatic index (2.49 ± 0.33%) and hepatosomatic index (2.15 ± 0.22%), whereas red tilapia displayed larger egg diameter (2.39 ± 0.35 mm) and greater fecundity (2978.33 ± 391.22 eggs/fish). Gene expression analysis revealed upregulation of growth-related genes (myoD, myogenin, IGF-1, IGF-2) in GIFT. Conversely, Nile tilapia exhibited upregulated myostatin expression (4.59 ± 0.06). Reproductive gene expression analysis showed higher levels of GnRH1 and GnRH2 in Nile tilapia, whereas GIFT exhibited elevated expression of KISS2 (5.75 ± 0.12), FSHβ (6.69 ± 0.11) and LHβ (4.60 ± 0.10), correlating with enhanced reproductive performance. Overall, the findings highlight the genetic and phenotypic superiority of GIFT and red tilapia, supporting their preferential in selective breeding programmes to enhance the aquaculture production.