REGULATION OF CRUSTACEAN MOLTING - A MULTI-HORMONAL SYSTEM

In order to increase in size, arthropods must first molt (shed) their confining exoskeleton. This molting process is under the immediate control of the steroid molting hormone 20-hydroxyecdysone (20-HE). Both the initial rise in circulating hormone concentration and a coordinated decline are necessary for successful molting. Synthesis and/or release of ecdysone, the precursor to 20-HE, is regulated by the neuropeptide molt-inhibiting hormone (MIH). We have determined the primary amino acid sequence of MIH in the lobster, Homarus americanus. This peptide has a high degree of identity with the lobster hyperglycemic hormone. Another endocrine factor that appears to be involved in molting is the juvenile hormone-like terpenoid methyl farnesoate (MF). We have characterized hemolymph MF binding proteins during the molt cycle. In addition, recent data indicate that MF may stimulate the secretion of 20-HE in vivo and in vitro.