Premeiotic endoreplication as a meiotic rescue mechanism in hybrid teleosts: candidate molecular switches, polyploid engineering, and aquaculture applications

Endoreplication is a conserved cell-cycle modification in which cells undergo repeated rounds of DNA replication without mitosis or cytokinesis, generating cellular polyploidy. This process contributes to cell growth, metabolic expansion, and developmental specialization across plants, invertebrates, and mammals. In teleost fish, whose genomes have been shaped by ancestral whole-genome duplications, endoreplication may have particular evolutionary significance. In hybrid fish systems characterized by genomic incompatibility, premeiotic endoreplication may serve as a meiotic rescue mechanism in some hybrid lineages that enables homologous chromosome pairing and circumvents hybrid sterility, as suggested by cytological evidence in female hybrid Clarias catfish ( Clarias macrocephalus × Clarias gariepinus ), where endoreplicated oocytes were observed in 12 of 372 pachytene cells (3.2%) and 45 of 142 diplotene cells (31.7%) from different females. This review synthesizes current knowledge on the molecular regulation of the endo-switch, for which suppression of Cyclin B/CDK1 and oscillatory Cyclin E/CDK2 activity are discussed as candidate regulatory features rather than an established Clarias mechanism, and discusses regulatory differences between pure endocycles and abortive endomitosis. We further evaluate approaches used to manipulate polyploidy in aquaculture, including physical shocks and chemical treatments used to induce polyploidy, while considering CRISPR/Cas9-based manipulation of CDK1 as an experimental functional approach rather than an established production method. Finally, we outline emerging multi-omics and artificial intelligence-based frameworks for predicting hybrid endoreplication potential and mitigating genomic instability, thereby bridging cell cycle regulation with precision aquaculture strategies. Collectively, these findings provide a mechanistic and applied framework that connects fundamental cell cycle mechanisms with the next-generation of polyploid-based aquaculture innovation.