Gamma radiation effects on the reproduction of the alfalfa weevil: I. response of age and sex

Abstract

When 2-, 3-, 4-, and 5-week-old male alfalfa weevils, Hypera postica (Gyllenhal), were irradiated with doses of 2,500 to 4,500 R via a Cobalt-60 source after mating with unairradiated females, doses higher than 3,500 R were shown to induce complete sterility in 3- and 4-week-old males over a 3-month period. In contrast, females irradiated at 3 and 4 weeks of age were resistant to sterilization compared with similarly aged males. These females showed 32 and 15 percent fertility, respectively, after treatment with 3,500 R and mating with unairradiated males. A dose of 4,500 R was required to completely sterilize the females.

The mating combinations most effective in reducing fertility were those in which the males were irradiated, that is, irradiated males mated with normal females (NxI8) or with irradiated females (IxI8) produced greater sterility than the INở pairs.

The irradiated females were less fertile than the non-irradiated ones. Doses above 4,500 R caused almost a complete cessation of egg production. Only 5 percent of the eggs laid by females irradiated with 3,000 R and mated with normal males developed to adulthood. No eggs laid by females irradiated with 3,500 R and similarly mated developed to adults

The survival of irradiated males 2 to 5 weeks old was unaffected by doses up to 4,500 R. Females, however, were unaffected for 90 days after irradiation, except at 4,500 R applied to 3-week-old females, which showed 100 percent mortality