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 stadium larval Lacanobia oleracea had no significant effect on larval growth, development or food consumption, compared to control injected insects. In contrast, injection of M. sexta allatostatin (Manse-AS) into fifth stadium larvae resulted in a retardation of growth, reduction in feeding and increased 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) synthesis to produce the observed effects, but most likely by its myoinhibiting action on the foregut. Inhibition of foregut peristalsis by Manse-AS in vivo appears to suppress feeding, resulting in increased mortality. Foregut peristalsis may be inhibited by the intact peptide or a deletion peptide produced by cleavage of Manse-AS by haemolymph enzymes, because Manse-AS (5-15) also inhibits muscle contractions in the foregut in vitro.