At the onset of dorsal closure, the alignment of cardial cells in embryos expressing prc^{IR.dsRNA.Scer\UAS} under the control of Scer\GAL4^prc.4.5 appears regular, as in wild-type embryos. However, as dorsal closure progresses, the cardial epithelium becomes disorganised. In many places the alignment of the cardial cells is interrupted by holes from which they are absent and clusters of cardioblasts are seen. Disorganisation of the pericardial cells also results in interruptions in the dorsal vessel and repeated clustering of the cells.