Kj. Siegert et al., CARBOHYDRATE AND LIPID-METABOLISM DURING THE LAST LARVAL MOLT OF THE TOBACCO HORNWORM, MANDUCA-SEXTA, Physiological entomology, 18(4), 1993, pp. 404-408
At 25-degrees-C and with a light regime of 17 h light and 7 h dark, th
e last larval moult of the tobacco hornworm, Manduca sexta, lasts appr
oximately 32 h, during which profound changes of metabolism were obser
ved. At the onset of the moult, which coincides with the cessation of
feeding, the proportion of active fat body glycogen phosphorylase incr
eased from 10 (-2 h) to 25-30% (0 h). A biphasic pattern with peak act
ivities of 45-50% after t = 12 h and again just prior to the shedding
of the cuticle (32 h) was subsequently observed. Haemolymph trehalose
concentration decreased significantly from c. 35 (0h) to 20 mm (8h), b
ut then recovered to an intermediate level (30 mm; 12 h). After comple
tion of the moult, the trehalose concentration was 35-40 mm. The haemo
lymph glucose level in feeding fourth instar larvae was 4-5 mm, but de
creased sharply before the onset of the moult to c. 1 mm, followed by
a slow 6-fold increase over the next 20 h. Prior to the shedding of th
e cuticle, the glucose level dropped again dramatically. The haemolymp
h lipid level increased slowly from an initial level of 1.2-1.4 mg/ml
during the early part of the moult, reaching a maximum of 1.8 mg/ml af
ter t = 16 h. Afterwards, a decrease of c. 50% was observed until ecdy
sis occurred. Oxygen consumption per animal decreased steadily from 30
-35 mul/min pre-moult by approximately 70% to c. 10 mul/min but starte
d to increase about 5 h before the animals resumed feeding.