a1 Joint FAO/IAEA Division of Isotope and Radiation Applications of Atomic Energy for Food and Agricultural Development, International Atomic Energy Agency, Vienna, Austria
The effects of gamma irradiation from a 60Co-source on Glossina palpalis palpalis (Robineau-Desvoidy) were established in laboratory tests. Dose-response data indicated that fecundity was reduced by about 95% following exposure of late stage puparia or young adults to 11–13 krad in air and 15–18 krad in a nitrogen atmosphere. None of the treatments had a detectable influence on the viability, mating behaviour, inseminating capability or competitiveness of the adult males.
When irradiated males were combined in varying ratios with untreated males and females, increasing numbers of sterile males resulted in a considerable reduction in pregnancy stages beyond the egg stage, an increasing proportion of parous females with an empty uterus due to expulsion of a dead embryo after embryonic arrest or due to ovary blockage and an increasing percentage of females with a degenerating egg in utero.
Remating of inseminated females with fertile males during the period when most of them had emptied their uterus (day 14–20) after embryonic arrest, had no noticeable effect on the sterility rate.
A most important consequence of recurring embryonic death was a detectable imbalance between intra-uterine and ovarian development. Some aberrations can be used as additional criteria for monitoring the effectiveness of sterile males released in the field.
Females irradiated in the pupal or adult stage displayed a normal receptivity and insemination rate and survived distinctly longer than untreated controls. Moreover, they built up abnormally abundant fat bodies and showed multiple mating scars (restricted to the palpalis group species) and completely atrophied ovaries.
It is postulated that the release-recapture and examination of the reproductive tract of irradiated females during an advanced stage of sterile release vector control operations would give evidence of mating that could expose the existence of relic wild populations, particularly when the natural tsetse population has been reduced to, levels below the threshold detectable by conventional techniques.
(Received November 10 1983)
(Revised March 29 1984)