Interaction between radiation effects, gravity and other environmental factors in Tribolium confusum

Multicellular organisms possess homeostatic control systems, which, in responding to changes of the external environment, modify the internal milieu of the organism accordingly, in order to make survival and normal physiological processes possible. This group has studied effects on physiological processes of single and combined environmental factors in the flour beetle, Tribolium confusum. Studies included low- and high-LET radiation, gravity compensation, near-weightlessness in space flight, ambient temperature, atmospheric composition, and magnetic field effects on the growth and development of Tribolium. For somatic effects, there appears to be a "normal physiological range" for each of these environmental variables; moreover, their effects seem independent of each other. When one of the listed environmental factors is near the limits of normal physiological tolerance, however, marked synergism has been observed between the effects of this factor and other environmental stresses. Fertilized Tribolium eggs showed a differential radiosensitivity to external irradiation, and a linear, dose-effect relationship was obtained, as accelerated heavy nitrogen and oxygen ions were used. Synergism was found when Tribolium were irradiated with ionizing radiation and subsequently exposed to temperature either below or above their normal physiological range. Gravity compensation or near-weightlessness in space flight have adverse effects on the development of Tribolium when an ambient temperature is near the higher or lower limit of tolerance. Similar results were observed when pupae were exposed to a combination of oxygen, temperature and magnetic field stresses.