In vivo effects of Manduca sexta allatostatin and allatotropin on larvae of the tomato moth, Lacanobia oleracea

Injection of Manduca sexta allatotropin (Manse-AT) into fifth or sixth stad ium larval Lacanobia oleracea had no significant effect on larval growth, d evelopment or food consumption, compared to control injected insects. In co ntrast, injection of M. sexta allatostatin (Manse-AS) into fifth stadium la rvae resulted in a retardation of growth, reduction in feeding and increase d mortality, compared to control injected insects, but had no effect on non -feeding (day 7) sixth instar larvae. Results suggest that Manse-AS is not acting on the corpora allata (CA) to inhibit Juvenile Hormone (JH) synthesi s to produce the observed effects, but most likely by its myoinhibiting act ion on the foregut. Inhibition of foregut peristalsis by Manse-AS in vivo a ppears to suppress feeding, resulting in increased mortality. Foregut peris talsis may be inhibited by the intact peptide or a deletion peptide produce d by cleavage of Manse-AS by haemolymph enzymes, because Manse-AS (5-15) al so inhibits muscle contractions in the foregut in vitro.