Fig. 1. The neuropeptide signalling pathway at eclosion. In response to decreasing levels of ecdysone, ecdysis-triggering hormone (ETH) is released, triggering the release of eclosion hormone (EH). These hormones act together in a positive-feedback loop, increasing the release of one another and regulating pre-ecdysis behaviour. EH causes the release of crustacean cardioactive peptide (CCAP), which shuts off pre-ecdysis and turns on the ecdysis motor program. At eclosion, CCAP causes release of bursicon, which binds to its receptor RK, and induces post-eclosion events by elevating levels of cAMP and causing tanning. This figure is modified from Clark et al. (Clark et al., 2004) and McNabb et al. (McNabb et al., 1997).