A STUDY OF SOME EFFECTS OF GAMMA RADIATION ON THE ADULTS AND EGGS OF AEDES AEGYPTI

¹ Naval Medical Research Institute, Bethesda 14, Maryland

1. It has been shown that when normal A. aegypti females are mated and given a blood meal 24 hours after exposure of the males to gamma radiation in doses up to 30,000 r, egg production is not significantly affected. If, however, mating is delayed 8 or 15 days following irradiation of the males, egg production decreases and the period of oviposition increases apparently because fewer males are able to copulate even though they still contain motile spermatozoa.

2. Although eggs continue to be produced in some quantity whether mating is immediate or delayed, fewer larvae hatch from eggs produced by females mated to males exposed to 2500 r, while a very few larvae hatch from eggs produced from matings in which the males received 10,000 r. However, it was possible to grow larvae successfully to fertile adults capable of mating and producing viable eggs only from matings in which the males had received a maximum of 7500 r.

3. It has been shown, too, that the egg production of female mosquitoes, exposed first to gamma radiation and mated 24 hours later to normal males, is significantly reduced among those receiving 2500 r, and almost entirely eliminated among those exposed to 10,000 r. However, larvae which could be grown to fertile adults were obtained only from eggs produced by females exposed to a maximum of 5000 r. When mating was delayed, no eggs were produced by females exposed to doses in excess of 3500 r, although viable larvae hatched from eggs of females exposed to 3500 r.

4. Females inseminated prior to being exposed to radiation produced approximately the same number of eggs at the various dosage levels as females inseminated subsequent to exposure. However, significantly fewer larvae hatched from these eggs than from the eggs laid by females inseminated subsequent to exposure.

5. To determine the effects of radiation during the cycle of egg development which occurs in A. aegypti following a blood meal, inseminated females were exposed to gamma radiation at various intervals following engorgement. It was found that egg production was almost entirely inhibited in females exposed to 10,000 r 4 hours after the blood meal, whereas it required in excess of 100,000 r to inhibit egg production in females in which exposure had been delayed 42 hours after the blood meal. On the other hand, although it required higher and higher doses of radiation to inhibit egg production the longer irradiation was delayed, nevertheless, the eggs became more and more sensitive to radiation as they matured within the body. Thus, whereas viable larvae resulting in fertile adults developed from eggs produced by females exposed to 5000 r 4 or 24 hours after the blood meal, viable larvae could be obtained from the eggs of females exposed to only 3500 r when exposure was delayed 42 hours.

6. Finally, it has been shown that although the dosage required to inhibit hatching of the eggs of A. aegypti exposed to gamma radiation varied enormously according to the age of the egg, nevertheless, eggs exposed to doses in excess of 2000 r, regardless of age, could not be grown to adults. Again, however, as in the experiments in which either males or females were exposed to radiation, whenever larvae could be grown successfully to adults, the resulting adults proved to be fertile and capable of producing viable eggs if they were physically capable of mating.