Nutritional ecology of a parasitic wasp: food source affects gustatory response, metabolic utilization, and survivorship

Authors: Williams, Livy; ROANE, TIMBERLEY - UNIV. COLORADO AT DENVER

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2007
Publication Date: 10/31/2007
Citation: Williams III, L.H., Roane, T.M. 2007. Nutritional ecology of a parasitic wasp: Food source affects gustatory response, metabolic utilization, and survivorship. Journal of Insect Physiology. 53:1262-1275.

Interpretive Summary: Plant bugs are serious pests of many crops, including cotton and soybean, in the United States. Beneficial insects are useful in killing plant bugs, but may require food sources, such as nectar, to maximize their potential. Thus, a better understanding of the nutritional requirements of beneficial insects has important implications for plant bug control. We conducted experiments to evaluate the suitability of naturally occurring sugars and a commercial food source for a beneficial insect that attacks plant bugs. Our results indicate that the beneficial insect fed on all 15 of the sugars. Sucrose, glucose, maltose, melezitose, fructose, trehalulose, and erlose led to the strongest feeding response. Eliminade™, a commercial food supplement, was also readily accepted by the insect. Digestion of sucrose, a common nectar sugar, was faster than that of melezitose, a sugar common in aphid honeydew, indicating specificity in the enzymatic machinery of A. iole. Lifespan was greater at 68°F than at 81°F, and at both temperatures survival was generally greatest for wasps provisioned with sucrose, glucose, and fructose. Honeydew sugars were highly variable in their effect on survival. Glucose, fructose, and several sugars composed of these smaller sugars appear to be more suitable for the beneficial insect than other sugars tested. Our findings suggest that benefits afforded by food sources are important for the insect to maximize its attack of pestiferous plant bugs.

Technical Abstract: The success of biological control is largely mediated by the longevity and reproductive success of beneficial insects. Nectar and honeydew can improve the nutrition of parasitic insects, and thereby increase their longevity and realized fecundity. Development of effective conservation biological control depends on knowledge of the insect’s nutritional physiology and ecology. We conducted experiments to examine the nutritional ecology of an egg parasitoid when provided with naturally-occurring sugars and a commercial food supplement. Anaphes iole showed strong gustatory perception of trehalulose, a carbohydrate found in homopteran honeydew. Enzymatic hydrolysis of sucrose, a common nectar sugar, was faster than that of melezitose, a sugar common in aphid honeydew, indicating specificity in the enzymatic machinery of A. iole. Longevity was greater at 20°C than at 27°C, and at both temperatures survival was generally greatest for wasps provisioned with the three major nectar sugars, sucrose, glucose, and fructose. Honeydew sugars were highly variable in their effect on survival. Comparison of survival with previously reported gustatory response data showed a positive correlation for most sugars. Glucose, fructose, and several oligosaccharides composed of these monosaccharide units appear to be more suitable for A. iole than other sugars tested. Evidence suggests that individual fitness benefits afforded by food sources are important for A. iole, a time-limited parasitoid.