Abstract
Parasitic wasps and their larval hosts are intimately connected by an array of behavioral adaptations and counter-adaptations. This co-evolution has led to highly specific, natural variation in learning rates and memory consolidation in parasitoid wasps. Similarly, the hosts of the parasitoids show specific sensory adaptations as well as non-associative learning strategies for parasitoid avoidance. However, these neuronal and behavioral adaptations of both hosts and wasps have so far been studied largely apart from each other. Here we argue that a parallel investigation of the nervous system in wasps and their hosts might lead to novel insights into the evolution of insect behavior and the neurobiology of learning and memory.
Highlights
Primary parasitoids and their larval hosts are intertwined in a constant arms race, which extends from immune responses to different behavioral strategies [1,2]
A first approach When herbivorous insect larvae initiate feeding, the chance of being attacked by a parasitoid or predator increases up to a hundred times as they have to give up their hiding places and because feeding triggers the release of volatiles, which are used by their natural enemy to locate their victims [5,6] (Figure 1.1)
Sensitization as a non-associative form of learning (Box 1) might help the host to avoid parasitoid enemies, but could play a role in the oviposition choice of the adult insect in a phenomenon known as the Hopkins host selection principle [12]; a learning mechanism in which the adult oviposition choice is influenced by larval experiences
Summary
Primary parasitoids and their larval hosts are intertwined in a constant arms race, which extends from immune responses to different behavioral strategies [1,2] Within this evolutionary conflict, the ability to learn is of paramount importance for both sides [3], especially when the behavior of the parasitoid or host changes due to climatic or other man-made influences on natural and agro-ecosystems [4]. If the caterpillars feed initially on the suitable but non-solanaceous cowpea Vigna sinensis, these plants will later on be accepted, solanaceous plants will still be preferred [8] This increased host-plant preference is at least partly due to sensitization of specific taste neurons, which increase their responses to indioside D, an important feeding stimulus present in many solanaceous plants, but absent in cowpea [10]. Most parasitoids are highly specialized on a certain insect host species [13] (Figure 1.1), and have an innate preference for plant odors induced by the feeding of their hosts, so-called herbivore-induced plant www.sciencedirect.com
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