The formation of a hybrid fish derived from Labeo rohita ♀ × Cyprinus carpio ♂ and exhibiting stronger low temperature tolerance

Temperature is a critical environmental factor that influences the distribution of species and impacts life activities such as development, growth, physiology, and metabolism. In China, the rearing range of Roho labeo (Labeo rohita) has been restricted due to its limited low temperature tolerance. In this study, a hybrid population, designated RLC, was produced from Labeo rohita (RL, 2n = 50) (♀) × Cyprinus carpio (CC, 2n = 100) (♂). Comparative analyses of morphological traits, DNA content, and chromosome numbers revealed that RLC (2n = 75) is a hybrid fish, with the genotype and phenotype distinct from its parent species. RLC demonstrated enhanced low temperature tolerance compared to RL, the CTmin (9.04 ± 0.83 °C) and T_LD50 (4.1 °C) for RLC were markedly lower than RL (12.08 ± 1.25 °C, 7.2 °C). Biochemical indices and histological analysis indicated that low temperature stress induced structural damage and oxidative stress in the liver, gills, and brain of both RLC and RL, with notable improvements in RLC compared with RL. The joint analyses of transcriptomics and metabolomics showed that metabolic pathways in the liver of RLC were most significantly impacted by low temperature stress. Additionally, regulation of lipid metabolism appears to be vital for the response of RLC to low temperature stress. Our findings contribute to the understanding of distant hybridization and the molecular mechanisms underlying the response to low temperature stress in fish.