Cobalt nanoparticles protect against endocrine disruption in response to multiple abiotic stresses in fish

Background Climate change, pollution, and deteriorating water quality have emerged as major threats to aquaculture and fish reproduction. Anabas testudineus were exposed to multiple abiotic stressors such as arsenic, ammonia toxicity, low pH, and elevated temperature, which disrupt endocrine regulation, impair reproductive hormones, reduce sperm quality, and ultimately decrease reproductive efficiency. These stressors adversely affect the hypothalamic-pituitary-gonadal axis, resulting in hormonal imbalance and poor gamete quality of fish. The present investigation aims to protect the fish against endocrine disruption and improve reproductive hormones by using cobalt nanoparticles diets (Co-NPs). Methods An experiment was conducted for 115 days in Anabas testudineus of five hundred and four (504) with an average weight of 9.54 ± 0.25 g. The experiment was designed with twelve treatments in triplicate. The experiment was conducted in the triplicate. Cobalt nanoparticles (Co-NPs) were synthesized using green approach and formulated fish diet at 0.2, 0.4, 0.6 and 0.8 mg kg-1 diet. The arsenic (1/10 th LC 50 , 2.05 mg L -1 ), ammonia (1/10 th of LC 50 2.3), low pH (6.5), and elevated temperature (34 °C) were maintained throughout the experiment for 115 days. The endocrine disruption, reproductive hormones and milt quality were evaluated. Results Reproductive hormones in both male and female fish such as gonadotropin-releasing hormone (GnRH), progesterone, 11-keto-testosterone (11-KT), follicle-stimulating hormone (FSH), luteinizing hormone-releasing hormone (LH-RH), vitellogenin (Vt), and estradiol (in females) were significantly improved with Co-NP supplementation at 0.4 and 0.6 mg kg - ¹ under both control and As+NH 3 +pH+T exposure conditions. Co-NPs supplementation also protects from endocrine disruption in the present study. Furthermore, milt/sperm characteristics were evaluated under multiple abiotic stressors and dietary Co-NP treatments. Milt count, milt motility, straight-line velocity (VSL), curvilinear velocity (VCL), progressive motility, average path velocity, linearity (%), and straightness (%) were substantially enhanced by dietary Co-NPs at 0.4 and 0.6 mg kg - ¹, with or without stress exposure. Conclusions Dietary supplementation of Co-NPs at 0.4 and 0.6 mg kg - ¹ demonstrated strong potential to improve reproductive efficiency in A. testudineus under combined abiotic stress conditions (As+NH 3 +pH+T).