Effects of Manduca diuresin on neonates of the tobacco hornworm, Manduca sexta

Manduca diuresin (MD), a 30 amino acid peptide, was isolated and identified from the type IIb median neurosecretory cells in the brain of adult Manduc a sexta (Blackburn et al., Biochem. Biophys. Res. Commun., 181, 927-932, 19 91). The synthetic hormone stimulates water loss in the adult moth both in vitro using isolated Malphigian tubule preparations and in vivo using decap itated adult moths as bioassay animals (Blackburn and Ma, Arch. Insect Bioc hem. Physiol., 27, 3-10, 1994). In the present study MD was shown to have a dverse physiological effects on neonates of Manduca sexta when fed syntheti c hormone-treated leaf discs. With a sustained diet of MD-treated discs, ne onates exhibited symptoms of reduced food consumption and marginal weight i ncreases. In addition to slowed growth and reduced developmental rates, a h igh percentage of these neonates failed to molt into second instar larvae a nd death usually followed shortly thereafter. This is a first report that a synthetic insect neuropeptide has shown detrimental effect on insect larva e by ingestion. The possibility of utilizing this peptide in plant protecti on is discussed. (C) 2000 Academic Press.