Mechanical analysis of a heat-shock induced developmental defect

Embryonic development in~\textit{Drosophila}~is a complex process involving coordinated movements of mechanically interacting tissues. Perturbing this system with a transient heat shock can result in a number of developmental defects. In particular, a heat shock applied during the earliest morphogenetic movements of gastrulation can lead to apparent recovery, but then subsequent~morphogenetic failure 5-6 hours later during~germ band retraction. The process of germ band retraction requires an intact amnioserosa -- a single layered extra-embryonic epithelial tissue -- and heat shock at gastrulation can induce the later opening of~holes in the amnioserosa. These holes are highly correlated with failures of germ band retraction. These holes could be caused by a combination of~mechanical weakness in the amnioserosa~or~local increases in mechanical~stress.~ Here, we assess the role of mechanical stress using confocal imaging to compare cell and tissue morphology in the amnioserosa of normal and heat-shocked embryos and laser hole drilling to map the stress field around the times and locations at which heat-shock induced holes open.~