SHORT-TERM AND LONG-TERM EFFECTS OF ENVIRONMENTAL UREA ON FECUNDITY IN DROSOPHILA-MELANOGASTER

Previous studies have shown that exposure to urea-supplemented food in hibited fecundity in Drosophila females, and that this inhibition was not expressed when females were given a choice between regular and ure a-supplemented food as an oviposition substrate. We assayed fecundity, on both regular food and urea-supplemented food, at 5, 15 and 25 days post eclosion on females from ten laboratory populations of Drosophil a melanogaster. The females assayed came from one of two treatments; t hey were maintained as adults on either regular or urea-supplemented f ood. We found that exposure to urea-supplemented food inhibited fecund ity, relative to the levels exhibited on regular food, regardless of w hether the urea was present in the assay medium, or in the medium on w hich the flies were maintained over the course of the experiment, ther eby suggesting that urea has both a long-term (possibly physiological) as well as a short-term (possibly behavioural) inhibitory effect on f ecundity of Drosophila females. We also tested and ruled out the hypot hesis that prior yeasting could ameliorate the inhibitory effect of ur ea in the assay medium on fecundity, as this was a possible explanatio n of why flies given a choice between regular and urea-supplemented fo od did not exhibit a preference for regular food in a previous study.