Third instar larvae collected about 18 hours before puparium formation and subjected to a single heat treatment at 37oC for 30 minutes (to induce expression of EcRdsRNA.hs.PL) followed by recovery at 25oC, all arrest development at the larval-prepupal transition, as stationary untanned elongated prepupae with everted anterior spiracles.
Heat-shock induced expression of EcRdsRNA.hs.PL results in a high degree of lethality. Two sequential heat treatments, at about 18 and 12 hours before puparium formation generates the most severe phenotype. 81% of these animals arrest development as stationary late third instar larvae. They also fail to shorten their body to form the characteristic shape of a prepupa and die several days later. About 13% attempt to pupariate but form long prepupae that occasionally fail to tan and dies 1-2 days later. 6% of animals die as pupae with defects in leg elongation. Dissection of prepupae reveals normal larval midguts in newly formed prepupae but the midguts fail to progress beyond the stage normally seen in prepupae that are 2 hours old. The midgut fails to contract and undergo cell death, resulting in persistence of the gastric caeca and proventriculus. In addition the adult midgut does not appear to form, and the salivary glands are still present 24 hours after puparium formation.