Space environment combined with radiation on Biosatellite II for 42 hours significantly enhanced two radiation effects in the developing flour beetle, Tribolium confusum. A developmental wing abnormality, appearing in adults following pupal irradiation, was increased to 44.8% in flight, compared with control incidence of 29.9%. Similarly, dominant lethals of offspring of females irradiated in space increased significantly to 78% from 27% on the ground. Postflight ground control tests indicate that weightlessness, not acceleration or vibration, was the contributing factor. The duration of the pupal stage was unaffected. All pupae were between 19 and 27 hours old at launch and preirradiated with 1350 R of 180-keV x-rays to place them into their sensitive dose range. Total irradiation received in space, from a${}^{85}{\rm Sr}$ γ-ray source, was approximately 950 R.

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