Response ofDrosophila tocis‐ andtrans‐22‐dehydrocholesterol II. Ability of sterols other than cholesterol to overcome the toxicity of thetrans isomer

Four species ofDrosophila were tested, for two generations, for viability on media containing 13 different C27, C28 and C29 sterols with and withouttrans‐22‐dehydrocholesterol. Only cholesterol was effective for overcoming the toxic effect of therans derivative for all 4 species. The species varied in their ability to use the 13 sterols for growth, maturation and reproduction for 2 generations. The most tolerant species.D. pseudoobscura, could use 11 of the 13 sterols for structural and hormonal functions, whereas the most sensitive species,D. mettleri, could survive adequately on only 4 and less than adequately on another 3 of the 13 compounds. Desmosterol could not be used by any species, even for 1 generation.