Radiation sterilization of Glossina tachinoides Westw. pupae. II. The combined effects of chilling and gamma irradiation

Abstract

Female and male Glossina tachinoides Westwood were exposed as 5-day-old pupae to 15°C for 9 to 21 days. Female pupal development was delayed at 10.4 and 18.4 days and male pupal development at 9.9 and 18.4 days for pupae incubated for 9 and 21 days respectively. Pupal eclosion was only affected by chilling periods exceeding 15 days. Mating response, insemination capacity and fertility of males exposed as pupae to a 9-day chilling period were not affected, but their survival was significantly reduced from 52.1 ± 26.2 days to 35.3 ± 18.8 days. Survival of adult females was reduced when exposed as pupae to chilling periods exceeding 12 days. After 9 days at 15°C, however, females produced 11 % less offspring than untreated females. Pupae, incubated for 9 days at 15°C when 5 or 10 days old, were irradiated with 10 and 20 Gy in air or nitrogen 1 h, 7 h, 1,3 and 5 days after the incubation treatment. In general, the eclosion rate, male fertility and average male survival were increased when the radiation treatment was given in nitrogen and when chilling and irradiation treatments occurred later in pupal life. Only males chilled for 9 days as 5-day-old pupae and irradiated with 10 Gy in air on day 20 PL (post larviposition) had a residual fertility below 5 % and lived on average longer than 20 days. Survival of all experimental female flies was reduced as compared with the control. Their receptivity to mating remained however normal in most cases. Complete sterility was induced in females, incubated at 15°C for 9 days as 5- day-old pupae and irradiated with 10 Gy in air on day 15 - 20 post larviposition and in females, incubated at 15°C for 9 days as 10-day- old pupae and treated with 10 Gy in air on days 20 or 21 of pupal life.