Effects of partial sugar deprivation on lifespan and carbohydrate mobilization in the parasitoid Macrocentrus grandii (Hymenoptera: Braconidae)

We compared the lifespan of Macrocentrus grandii (Goidanich) adults fed a 50% sucrose solution at various intervals throughout their lives. Treatments included starvation, continuous feeding, feeding on the first day of life only, and feeding every second, third, or fourth day of life. Life expectancy for starved males and females was less than 3 d, and providing sugar during the first day of life increased life expectancy by 2 d for males and 4 d for females. Life expectancy was highest when adults were fed continuously (14 d for males and 21 d for females) or every 2 d (17 d for males and 23 d for females). The life expectancy of adults that were fed either every 3 or every 4 d ranged between 9 and 16 d. Together, these results demonstrate that a constant supply of sugars is not necessary to achieve maximum survivorship, and limited sugar availability may suffice to increase substantially the lifespan of M. grandii over starvation values. A series of anthrone tests was used to determine levels of gut sugars, simple storage sugars ('body sugars'; primarily trehalose), and glycogen over the first 6 d of life of female and male M. grandii that were either fed 50% sucrose continuously, the first day of life only, or not at all. A single day of sugar feeding led to apparently maximum levels of gut sugars, body sugars, and glycogen, and parasitoids fed only on the first day of life maintained high levels of these nutrients for 1 d postfeeding. After this time, glycogen and gut sugars decreased substantially, but body sugar levels remained essentially constant. This pattern suggests a strategy in which gut sugars and glycogen are mobilized to maintain high levels of body sugars in starving parasitoids.