Carbohydrate Use in the Flight Muscles of Manduca Sexta During Pre-Flight Warm-Up

Abstract

ABSTRACT Although fat is the principal fuel for flight in moths and butterflies, some use of carbohydrate fuels during activity would be predicted on energetic and biochemical grounds, particularly in nectivores. The present study evaluates the use of carbohydrate fuels during pre-flight warm-up in the endothermic sphinx moth Manduca sexta (L.). Carbohydrate content of moths was measured at intermediate points during the pre-flight warm-up cycle and at take-off. Muscle glycogen content declined during the initial phases of warm-up, whereas glucose and trehalose concentrations were unchanged. Abdominal carbohydrates were not mobilized during warm-up. Energy budget analysis suggests that glycogen oxidation supplies about 39% of the energy needed for the initial phase of warm-up and about 6% of the total cost of warm-up. Glycogen use during warm-up may be correlated with the capacity for endothermic warm-up at low ambient temperatures. Carbohydrates appear to be more important as fuels for activity in some lepidopterans than has been previously reported for other members of this diverse Order.