GENETICS OF LARVAL UREA TOLERANCE IN DROSOPHILA-MELANOGASTER

The genetic control of larval tolerance to urea, a nitrogenous waste-p roduct occurring naturally in crowded Drosophila cultures, was investi gated in a set of five laboratory populations of D. melanogaster that had been successfully subjected to selection for increased larval urea tolerance. Larva to adult survivorship and development time at three different levels of urea were assayed on the five selected populations , their five matched controls and a set of 10 F-1 hybrid populations d erived from reciprocal crosses between pairs of selected and control p opulations. As expected from the results of previous studies, the sele cted populations exhibited greater larval tolerance to the toxic effec ts of urea, relative to their controls. Comparison of the hybrid and p arental populations with respect to both survivorship and development time indicated that the genetic control of urea tolerance in the selec ted populations is largely dominant, and has a significant X-linked co mponent. The data also suggested that females from the selected popula tions exercise a nongenetic maternal effect on the development time of their progeny, regardless of urea level.