Effect of Ionizing Radiation on the Population Kinetics of the Snail Australorbis glabratus: Age at Exposure and the Effects on Reproduction

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Abstract
Degenerative changes in the reproductive system of the hemaphroditic snail after irradiation was investigated. The reproductive capability, which was reduced by radiatio in all animals, followed approximately the same pattern of age and dose dependency as growth, except for a second peak of radiosensitivity in old animals. Newborn animals showed much greater damage than juveniles, and changes produced in young juveniles were greater than in older juveniles. However, there is a second peak of radiosensitivity in animals 210 days old. Although damage to the ovaries, as shown by delayed and reduced egg depositions, was reparable within 3 to 5 months in animals irradiated prior to maturation, fecundity required a longer period to return to normal levels. Although fecundity was only impaired in newborn and old animals, fertility was completely abolished after exposure to certain amounts of radiation. Irreparable damage to fertility was reduced when radiation was given the onset of sexual maturity. Nevertheless, fertility was greatly reduced in these animals, thus suggesting some deleterious radiation effects in the germ cell. Heritability of these effects, as shown by reduced fecundity in the immediate offspring of irradiated parents, confirmed the concept of radiation injury to the germ cell being genetic in nature. The offspring of irradiated snails were less affected than their parents. Naturally occurring growth retardation contributed to the increase of sensitivity of the gonadal tissue to radiation.