The role of neuropeptides in regulating ecdysis and reproduction in the hemimetabolous insect Rhodnius prolixus

In ecdysozoan animals, moulting entails the production of a new exoskeleton and the shedding of the old one during ecdysis. It is induced by a pulse of ecdysone that regulates the expression of different hormonal receptors and activates a peptide-mediated signalling cascade. In Holometabola, the peptidergic cascade regulating ecdysis has been well described. However, very little functional information regarding the neuroendocrine regulation of ecdysis is available for Hemimetabola, which displays an incomplete metamorphosis.

Here, we studied neuropeptides related to ecdysis regulation in the hemi-metabolous insect Rhodnius prolixus. The RNA interference-mediated reduction of ETH expression in fourth instar nymphs resulted in lethality at the expected time of ecdysis, thereby showing its crucial role in this process. Furthermore, the results revealed the involvement of ETH in the regulation of reproductive fitness. Different from holometabolous, the knockdown of ETH in adult females led to failures in egg hatching without affecting the oviposition. Most of the first instar nymphs hatched from the eggs laid by females injected with dsEH, dsCCAP and dsOKA died at the expected time of ecdysis, indicating the crucial involvement of these genes for post-embryonic development. No phenotypes were observed upon CZ knockdown in nymphs or adult females. The conservation of the role of these neuropeptides in regulating ecdysis and reproduction throughout the class Insecta is discussed.