Effect of Gamma Radiation on Tissues of the Tobacco Budworm, Heliothis virescens1,2

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Abstract
Fifth stage larvae and 6-day-old pupae of H. virescens (F.) were irradiated with a cobalt-60 source. Damage to various organs was studied. Testes and wing pads appeared to be the most sensitive tissue in both larvae and pupae. Radiation caused some of the epidermal cells of the developing wing pads to enlarge causing an irregular adult cuticle to be produced. Radiation also caused the production of bridges of cuticle between the upper and lower lamellae of the wing pads which prevented the expansion of the adult wing. Death in the pupal stage was often due to failure of the adult to free its wings from the pupal case. Larvae stopped feeding following irradiation, the midgut cells enlarged and later disintegrated. Midgutcell replacement was curtailed. The peritrophic membrane was reduced or absent possibly because of damage to the secretory cells. Fat body cells appeared to be depleted of their stored nutrients. The cuticle failed to separate from the epidermal cells. This failure may have been due to radiation affecting the production of hormones in the endocrine system or enzymes involved indigestion of the old cuticle. Death of larvae following irradiation appeared to be due to failure to molt at higher doses and to energy depletion which may also account for the reduced adult life span. Irradiation effects on testes were noted, and chromosomal bridging was observed in the germ cells.

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