Olfactory learning in a parasitic wasp

Durrant, Lisa F (2007) Olfactory learning in a parasitic wasp. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

In numerous past studies, parasitic hymenoptera species have demonstrated sophisticated learning abilities particularly when associating chemical odours with a reward (e.g. Lewis and Takasu, 1990; Turlings et al., 1993a). This type oflearning is termed associative learning and can be defined as "The process by which animals learn about casual relationships between events and behave appropriately as a result" (Dickinson, 1980). The parasitic wasp Cotesia plutellae is part of a tritrophic system in which it utilises chemical cues from the food plant of its host, Plutella xylostella, in order to locate this host more effectively. This study investigates how behaviour changes as a response to the learning of these volatile chemicals. Initial experiments determine whether learning of chemical odours from the Chinese cabbage occurs and how learning modifies preference for a particular odour. The study then focuses on which particular chemicals in the profile are important for learning and whether chemicals outside the insect's natural foraging range can be learnt. The results suggest that learning does occur in this species and that actively released plant volatiles playa particularly important in role. The sesquiterpene (E)-B-caryophyllene may be a key component in learning, although it is likely that a combination of chemicals are more effective. Cotesia plutellae appears to learn a novel chemical vanillin, which does not normally occur in its foraging range. Bioassays showed that as well as spending more time in the appropriate odour field, experienced parasitoids may decrease their velocity and increase meander. Applications of this research are discussed.

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