Abstract
Animals have evolved cognitive abilities whose impairment can incur dramatic fitness costs. While malnutrition is known to impact brain development and cognitive functions in vertebrates, little is known in insects whose small brain appears particularly vulnerable to environmental stressors. Here, we investigated the influence of diet quality on learning and memory in the parasitoid wasp Venturia canescens. Newly emerged adults were exposed for 24 h to either honey, 20% sucrose solution, 10% sucrose solution, or water, before being conditioned in an olfactory associative learning task in which an odor was associated to a host larvae (reward). Honey fed wasps showed 3.5 times higher learning performances and 1.5 times longer memory retention than wasps fed sucrose solutions or water. Poor diets also reduced longevity and fecundity. Our results demonstrate the importance of early adult nutrition for optimal cognitive function in these parasitoid wasps that must quickly develop long-term olfactory memories for searching suitable hosts for their progeny.
Highlights
We tested whether diet quality during early adulthood affect the cognitive performances of V. canescens wasps, a thelytokous, koinobiont and solitary endoparasitoid of lepidopterous larvae[28,37,38]
Recent studies showed that a lack of specific n utrients[21,22] or an unbalanced ratio of these n utrients[20] in food can result in impaired cognitive abilities in model insect species, such as honey bees and fruit flies
We found that olfactory learning performances and memory retention times of V. canescens wasps were considerably affected by a poor diet soon after adult emergence
Summary
We tested whether diet quality during early adulthood affect the cognitive performances of V. canescens wasps, a thelytokous (i.e. a type of parthenogenesis in which unfertilized eggs produce females), koinobiont (i.e. the host continues to feed and grow after parasitization) and solitary endoparasitoid of lepidopterous larvae[28,37,38]. We experimentally exposed emerging females to one of four nutritional conditions of decreasing quality in terms of nutrient concentration, nutrient diversity, and energy content: honey (see composition in Table 1), sucrose 20%, sucrose 10%, and water. We tested the impact of diet on cognition in a conditioning assay in which wasps had to associate an odor to a host reward (larvae of Ephestia kuehniella) in a flight tunnel.
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