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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #183477
Title: GUSTATORY RESPONSE AND APPETITIVE LEARNING IN MICROPLITIS CROCEIPES IN RELATION TO SUGAR TYPE AND CONCENTRATION

Author
item WACKERS, FELIX - NETHERLANDS INST ECOLOGY
item BONIFAY, CLAIRE - UNIVERSITY OF GEORGIA
item VET, LOUISE - NETHERLANDS INST ECOLOGY
item Lewis, Wallace

Submitted to: Animal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2005
Publication Date: 3/31/2006
Citation: Wackers, F., Bonifay, C., Vet, L., Lewis, J. 2006. Gustatory response and appetitive learning in Microplitis croceipes in relation to sugar type and concentration. Animal Biology. 56(2):193-203.

Interpretive Summary: A better understanding and use of natural enemies of agricultural pests is important to developing effective alternatives to the economic costs and environmental hazards of conventional pesticides. ARS scientists at Tifton, GA together with their cooperators, are studying how plants provide nectar resources to optimize the host/ pest-finding efficiency of parasitic wasps such as Microplitis croceipes, a natural enemy of the bollworm/ corn earworm. Earlier studies have shown that when the wasps feed on nectar or other sugar sources while smelling an odor(s), they associative link the odor(s) to the sugar taste and subsequently respond to those odor(s). This study showed how the taste of some sugars are more effective in eliciting this learning link. Thus, plants with nectar of the proper sugar quality will be more effective in recruiting and sustaining the foraging efficacy of their natural enemy allies. This knowledge of how plant nectar and other mechanisms mediate interactions with parasitic wasps is an important step in developing improved strategies for biologically-based pest management of agricultural crops.

Technical Abstract: The parasitoid Microplitis croceipes can be conditioned to respond to odours through associative learning. Learning efficacy is known to depend on the type of the conditioned stimulus. Here we investigate to what extent appetitive conditioning is also affected by characteristics of the unconditioned stimulus. We tested 1M solutions of eight sugars naturally occurring in nectar and honeydew with respect to their effect on parasitoid gustatory response and their suitability as an unconditioned stimulus in the process of associative odor learning. To test for concentration effects, a separate experiment compared parasitoid performance with 1M and 1/4M of sucrose respectively. Only exposure to glucose, fructose, sucrose and melezitose enhanced feeding relative to control individuals provided water. Raffinose, mannose, galactose and melibiose did not increase or decrease consumption, indicating that these sugars are neither phagostimulants nor phagodeterrents. In the conditioning experiments, parasitoids that had been trained with the stimulatory sugars showed a clear conditioned response to the cineole. Conditioning with galactose, mannose and melibiose, on the other hand, did not lead to successful odor acquisition. Conditioning with raffinose increased the parasitoid's tendency to exhibit a conditioned response, even though this response was significantly shorter than the response following training with stimulatory sugars. Learning was not significantly influenced by the concentration of a sucrose solution, even though the feeding response was significantly lower in the case of the 1/4M concentration. Our findings indicate that appetitive learning primarily involves gustatory reception. The results with raffinose indicate that post-ingestive feedback may be involved in food associative learning as well.