Hormones involved in the regulation of metamorphosis

Abstract The most important hormones in the regulation of insect metamorphosis are the molting hormone, which is produced by the prothoracic gland (PG) and induces molting, and the juvenile hormone (JH), which is produced in the corpora allata (CA) and represses metamorphosis. The molting hormone is an ecdysteroid, whereas the JH is an acyclic sesquiterpenoid. The most important factors stimulating the production of ecdysteroids in the PG are the prothoracicotropic hormone and the insulin-like peptides. Moreover, other peptides stimulate or inhibit ecdysone production. The best characterized are three prothoracicostatic factors: prothoracicostatic peptide, bommo-myosuppressin, and bommo-FMRF-amide-related peptides, and the prothoracicotropic activity of the pigment-dispersing factor. JH can also inhibit ecdysone production in certain conditions, and biogenic amines have also been involved in the regulation of PG activity. JH production is regulated by neuropeptides that stimulate (allatotropins) or inhibit (allatostatins) the CA activity. The ecdysis, or shedding off the exuviae during molting, requires a complex behavior regulated by peptides produced in Inka cells and the central nervous system. The most important are the ecdysis triggering hormone, the crustacean cardioactive peptide, the eclosion hormone, and corazonin. Then, in the tanning process that follows the ecdysis, an important player is the peptide bursicon.