North African catfish (Clarias gariepinus) is integral to aquaculture, particularly in hybrid production with bighead catfish (Clarias macrocephalus). Recent declines in their production output have been linked to the quality of the parental sperm. This study aimed to evaluate the state of spermatogenesis in two morphological testis forms, normal white testes (CGA_A) and black-brown testes (CGA_B), in captive populations to understand their differences in the cytological processes of spermatogenesis and impact on sperm quality and fertility. We performed computer-assisted sperm analysis (CASA), meiotic chromosome analysis, gene expression profiling, histological examination, and identification of apoptotic cells using the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Additionally, microsatellite genotyping was conducted to assess genetic diversity of the populations, showing that similar gene pool patterns were observed between the two populations with the CGA_A and the CGA_B testes. The average sperm motility was 11.15 %. Histologically, the CGA_A testes predominantly contained spermatozoa. By contrast, the CGA_B testes, characterized by black-brown color and harder texture, were composed mainly of spermatocytes and exhibited a higher incidence of apoptotic spermatogonia. Additionally, the CGA_B testes displayed reduced expression of genes essential for normal testicular development. Notably, the CGA_A testes showed significantly higher expression of GtH I, GtH II, Dazl, and Cxcr4b genes and lower levels of Caspase-3 and p53 (p < 0.05). The selective removal of deficient spermatogonia through early apoptosis in CGA_B testes suggest a mechanism contributing to male infertility due to imbalances between the number of germ cells and Sertoli cells. Despite the use of CGA_A testis for fertilization, a hatching rate in the captive populations was 36.43 % over the last three years (2021−2023), substantially lower than that previously reported, indicating the presence of genetic and environmental factors that influence reproductive success in North African catfish. Differences in spermatogenesis between testis forms highlight the need for genetic and environmental strategies to enhance reproductive outcomes in aquaculture.
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