Ionizing radiation effects on sex steroid hormone levels in serum and milt of freshwater fish Oreochromis mossambicus

• Gamma irradiation effects on steroid hormones were assessed in fish.
• Fishes were irradiated with 10, 15, and 20 Gy 60Co.
• Testosterone, 11-KT and 17β-estradiol levels decreased with higher dose.
• Biomonitoring study for radionuclides in aquatic environment.

Effects of gamma rays on the sex steroid hormone levels [testosterone (T), 11-ketotestosterone (11-KT) and 17β-estradiol (E2)] were studied in the freshwater fish Oreochromis mossambicus. Gamma radiation induced effects on hormone levels reported here for the first time in the fish. Since radionuclides released accidentally or during a nuclear disaster can contaminate inland water bodies, biomonitoring methods are required for assessing the impacts of certain dose levels of radiation that may ultimately result in ionizing radiation exposure to both humans and non-human biota. Three groups of (n=15 in each group) fishes were irradiated with a single dose of 60Co 10 Gy, 15 Gy and 20 Gy with a duration of .33, .50 and .66 min. Significant decrease of the hormone levels was seen at higher doses of 15 Gy and 20 Gy. The sex steroid hormone levels in the fishes are vital for sperm production, development, differential functions related to the physiology and reproductive behavior. This study serves as biomonitoring tool to assess the ionizing radiation effects on reproductive behavior of aquatic biota.