Fig. 3. Effect of expression of tetanus toxin (TNT) in the Gyc-89Da and Gyc-89Db neurons on survival during development. Flies expressing GAL4 under the control of the Gyc-89Da and Gyc-89Db promoters (p89Da-GAL4 and p89Db-GAL4, respectively) were crossed with flies expressing the active (TNTa) and inactive (TNTi) forms of the light chain of tetanus toxin (TNT) under the control of the UAS promoter (UAS-TNTa and UAS-TNTi, respectively) and the survival of the progeny determined at the stages shown. Survival rates for progeny of UAS-TNTa flies are shown with solid lines and those for progeny from UAS-TNTi flies with broken lines; those from p89Da-GAL4 flies are shown by filled symbols and those from p89Db-GAL4 flies by open symbols. The data represent the percentage survival calculated from the number of eggs laid and are the mean ± s.e.m. of at least three trials using up to 300 progeny per trial. For each developmental stage the experimental and control groups were compared statistically using Student's paired t-tests and asterisks indicate P<0.05.