The differential sensitivity of flour beetles,Tribolium confusum andT. castaneum to x-ray alteration of reproductive abilities, induced dominant lethals, biomass and survival

Some aspects of growth are reported for x-rayed populations of wild-type flour beetles cultured as single- or mixed-species. Irradiation with 250-kv x rays was carried out at 1 kr/min to total doses of 2, 4, or 6 kr. Reproductive abilities, measured as the mean number of F/sub 1/ adults per female, for single- species populations of T. castaneum given 2 hr approached control values after one month, whereas those of T. confusum persisted below controls. Four kr was almost sterilizing, over 90 and 99% sterilizing respectively for T. castaneum and T. confusum, while 6-kr doses induced complete sterility in both species. Dominant lethals induced by 2 kr were approximately twice as abundant in T. confusum as in T. castrneum. Increased fertility with time was considered evidence that undifferentiated gametes were more radioresistant than mature ones. Selective elimination of a flur beetle species (T. confusum) in coexistence was indicated at exposures greater than 4 kr of x rays but less than 6 kr. Interspecies antagonism and 2-kr irradiation, as an environmental stress factor, appeared additive in adversely influencing the reproductive ability of T. confusum. The dose-response curves for reproduction were linear up to 4 kr except for T. confusum. After 4more » kr the dose-response curves departed from linearity for both species. Biomass (standard dry wt) of F/sub 1/ adults decreased with increasing dose; however, the weight of individuals was not altered. Parental mortality was not affected at 2 and 4 kr; 94 to 100% were alive at 10 weeks. In the 6-kr group, 75 and 58% of T. confusum were alive in the single- and mixed-species populations, respectively, indicating that irradiation and coexistence reduced survival. Thus, these 2 organisms of similar biology differed radiologically, as seen by the overall greater radioresistance of T. castaneum compared with that of T. confusum. The one more pair of chromosomes in T. castaneum probably does not satisfy a genetic interpretation of radioinduced damage, but physiologic and cytogenetic factors may be responsible. (BBB)« less