Effects of Gamma Radiation on a Spider Mite, Tetranychus arabicus. 1. Irradiation of Eggs1

Abstract

Eggs of Tetranychus arabicus Attiah of 2 different ages were exposed to gamma rays from cobalt-60, and hatchability depended on age at treatment. Eggs irradiated at an early stage of embryonic development (1 day old) were considerably more susceptible than those exposed at the later stage (4 days old). Dosages of 9052 and 70,000 rad prevented egg hatching in 1- and 4-day-old eggs, respectively. Unfertilized eggs were more sensitive to radiation injury than fertilized eggs. Retardation in embryonic and postembryonic growth was noticeable. Mortality was high in larvae and in nymphs that hatched from irradiated eggs. Many emerged adults were malformed and showed a fusion of tarsal segments. Sublethal doses of 3224 and 14,086 rad significantly reduced fecundity and fertility of adults which emerged from 1- and 4-day-old irradiated eggs, respectively. Irradiation of 4-day-old eggs at 35,000 rad resulted in non-ovipositing females. Adult longevity was affected adversely. Males were more sensitive to radiation damage than females. Dosage of 3224 and 14,086 rad inhibited emergence of males from irradiated 1- and 4-day-old eggs, respectively.