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<p>This study aimed to determine the effects of sublethal concentrations of ammonia on the pituitary–gonadal axis and gonadal tissue changes in Nile tilapia. Following adaptation, 60 Nile tilapias with an average weight of 200 ± 10&#xa0;g were divided into 4 × 15 with 3 replications, including control and 3 experimental groups. Fish were exposed to various ammonia concentrations (10%, 20%, and 30% of LC50 96&#xa0;h) for 14&#xa0;days. After anesthesia and blood sampling from the caudal stalk vein, gonad specimens were fixed in Bouin’s solution for 48&#xa0;h. Tissue preparation involved slicing 4–6&#xa0;µm-thick sections and staining them with hematoxylin and eosin (H&amp;E). Microscopic results showed degeneration of oocytes and spermatocytes, tubular and follicle atresia, and vacuolation. Histomorphometric observations indicated a reduction in the gonadosomatic index (GSI), testes diameter, seminiferous tubular diameter, and ovarian and follicle diameter, while follicular atresia increased. EIA and ELISA methods showed increased FSH and LH levels and decreased testosterone, 17-β estradiol, and progesterone. It appears that sub-lethal ammonia concentrations caused pathological lesions in the testes and ovaries of N. tilapia and interfered with the pituitary–gonadal axis. These findings suggest that tissue damage and hormonal interactions are dose-dependent, with more severe complications observed at higher ammonia concentrations.</p>

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Hormonal and histopathological alterations in Nile tilapia, Oreochromis niloticus exposed to sublethal concentrations of ammonia

  • 期刊论文

  • 发表日期：

    2025年5月1日

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  • Anis Esmaili-Manesh,
  • Rahim Abdi,
  • Rahim Peyghan,
  • Mohammad Ali Salari-Aliabadi

摘要

This study aimed to determine the effects of sublethal concentrations of ammonia on the pituitary–gonadal axis and gonadal tissue changes in Nile tilapia. Following adaptation, 60 Nile tilapias with an average weight of 200 ± 10 g were divided into 4 × 15 with 3 replications, including control and 3 experimental groups. Fish were exposed to various ammonia concentrations (10%, 20%, and 30% of LC50 96 h) for 14 days. After anesthesia and blood sampling from the caudal stalk vein, gonad specimens were fixed in Bouin’s solution for 48 h. Tissue preparation involved slicing 4–6 µm-thick sections and staining them with hematoxylin and eosin (H&E). Microscopic results showed degeneration of oocytes and spermatocytes, tubular and follicle atresia, and vacuolation. Histomorphometric observations indicated a reduction in the gonadosomatic index (GSI), testes diameter, seminiferous tubular diameter, and ovarian and follicle diameter, while follicular atresia increased. EIA and ELISA methods showed increased FSH and LH levels and decreased testosterone, 17-β estradiol, and progesterone. It appears that sub-lethal ammonia concentrations caused pathological lesions in the testes and ovaries of N. tilapia and interfered with the pituitary–gonadal axis. These findings suggest that tissue damage and hormonal interactions are dose-dependent, with more severe complications observed at higher ammonia concentrations.