Sex-specific responses of small RNAs and transposable elements to thermal stress in zebrafish germ cells

Environmental fluctuations influence heritable phenotypes through complex molecular mechanisms. In zebrafish (Danio rerio ), the interplay between temperature variation, transposable element (TE) activity, and small RNA (sRNA) regulation in the germline remains underexplored. Here we exposed adult zebrafish to elevated temperatures and performed integrated genomic, transcriptomic, and sRNA profiling of testes and ovaries. We observed sex-specific responses: ovaries exhibited enhanced protein-processing pathways and robust miRNA and piRNA-mediated TE suppression, whereas testes showed immune-related signatures, reduced piRNA output, and increased de novo TE insertions preferentially within introns. These coordinated changes link environmental stress to genomic and epigenetic modulation, suggesting mechanisms by which populations may rapidly adapt to fluctuating conditions. Our findings provide insight into sex-biased germline resilience and highlight the role of TE dynamics and sRNA pathways in mediating thermal adaptation.