Gonadal Development and Differentiation of Hybrid F1 Line of Ctenopharyngodon idella (♀) × Squaliobarbus curriculus (♂)

The hybrid F₁ offspring of <i>Ctenopharyngodon idella</i> (♂) and <i>Squaliobarbus curriculus</i> (♀) exhibit heterosis in disease resistance and also show abnormal sex differentiation. To understand the mechanism behind gonadal differentiation in the hybrid F₁, we analyzed the transcriptomes of <i>C. idella</i>, <i>S. curriculus</i>, and the hybrid F₁; screened for genes related to gonad development in these samples; and measured their expression levels. Our results revealed that compared to either <i>C. idella</i> or <i>S. curriculus</i>, the gene expressions in most sub-pathways of the SNARE interactions in the vesicular transport pathway in the hypothalamus, pituitary, and gonadal tissues of their hybrid F₁ offspring were significantly up-regulated. Furthermore, insufficient transcription of genes involved in oocyte meiosis may be the main reason for the insufficient reproductive ability of the hybrid F₁ offspring. Through transcriptome screening, we identified key molecules involved in gonad development, including HSD3B7, HSD17B1, HSD17B3, HSD20B2, CYP17A2, CYP1B1, CYP2AA12, UGT2A1, UGT1A1, and FSHR, which showed significant differences in expression levels in the hypothalamus, pituitary, and gonads of these fish. Notably, the expression levels of UGT1A1 in the gonads of the hybrid F₁ were significantly higher than those in <i>C. idella</i> and <i>S. curriculus</i>. These results provide a scientific basis for further research on the gonadal differentiation mechanism of hybrid F₁ offspring.