CARBOHYDRATE-METABOLISM DURING THE PUPAL MOLT OF THE TOBACCO HORNWORM, MANDUCA-SEXTA

During the pupal molt of the tobacco hornworm, Manduca sexta, the perc entage of active fat body glycogen phosphorylase increased from 5-10 t o 20%, but only for a period of 5 h prior to the moll. From the time o f the appearance of two sclerotized dorsal bars to the time of the mol t, the concentration of total hemolymph carbohydrates doubled to 100 m M trehalose. Initially, the glucose level was high (16 mM) when compar ed with feeding larvae (approximately 1 mM) but decreased to zero just prior to the molt. The amount of cuticular chitosan decreased from ap proximately 100 mg to 10 mg al pupation; the exuvia contained approxim ately 7 mg. While the levels of total lipids in hemolymph were not aff ected, the lipid content of the fat body decreased significantly prior to the molt but increased sharply thereafter. Fat body glycogen phosp horylase in pharate pupae and pupae of M. sexta was substantially acti vated by the Manduca adipokinetic peptide hormone, which in pharate pu pae, produced the same response al 2 and 20 pmol per insect as in liga ted larval abdomens. In pupae the response was clearly reduced. Using chilling to stimulate glycogen phosphorylase, it was found that the en zyme in pharate pupae and pupae responded both in vivo and in vitro as in ligated abdomens of larvae. Thus, a transition to the adult respon se seems to occur during the pupal and pharate adult development. (C) 1995 Wiley-Liss, Inc.