Establishment of cold tolerance in Nile Tilapia (Oreochromis niloticus) next generation

Abstract

The optimal growth temperature for most tilapia species ranges between 25 and 28°C, with survival becoming critical at temperatures below 10-12°C. This study focused on developing a cold-tolerant generation of Nile tilapia (G9 strain) from WorldFish, Abbassa. Tilapia fingerlings were reared under winter conditions at two different locations in Egypt. Survivors were then transferred to the Central Laboratory for Aquaculture Research (CLAR) greenhouse, where they were prepared as breeders. In the first group, 58 males and 42 females were identified from 100 fish in the 1st pond, and 54 males and 46 females from 100 fish in the 2nd pond. In the second group, 45 males and 40 females were found among 85 fish in the 3rd pond, and 45 males and 31 females among 87 fish in the 4th pond. Tissue samples were collected daily from both susceptible and resilient fish for genomic analysis, utilizing DNA isolation and whole-genome sequencing at the University of Maryland, USA. Molecular characterization of muscle atrophy associated with starvation in tilapia revealed 4,833 differentially expressed genes (DEGs) compared to the control group, including 34 miRNAs and 460 lncRNAs. Gene ontology analysis identified 27 upregulated and 52 down-regulated biological processes related to muscle structure development and cellular macromolecule metabolism. The results have successfully produced a cold-tolerant tilapia generation that can be utilized in hatcheries to mitigate cold related mass mortality. This study provides valuable insights into the genetic basis of cold tolerance in Nile tilapia and offers potential for improving aquaculture productivity in regions with cooler climates.