Gamma radiation induced micronuclei and erythrocyte cellular abnormalities in the fish Catla catla

► LD50/30 determination in the Indian fish Catla catla. ► Gamma radiation induced dose rate dependent increase in micronucleus incidence and significant correlation with nuclear anomalies. ► Increased incidence of nuclear buds and tailed nuclei are the remnants of nucleoplasmic bridges. ► Acute exposures induced apoptosis while protracted exposures allow sufficient time for DNA repair.