Carbon dioxide narcosis modifies the patch leaving decision of foraging parasitoids

Gleaning information is a way for foragers to adjust their behavior in order to maximize their fitness. Information decreases the uncertainty about the environment and could help foragers to accurately estimate environmental characteristics. In a patchy resource, information sampled during previous patch visits is efficient only if it is retained in the memory and retrieved upon arrival in a new patch. In this study, we tested whether the braconid Asobara tabida, a parasitoid of Drosophila larvae, retains information gleaned on patch quality in the memory and adjusts its foraging behavior accordingly. Females were anesthetized with CO₂ after leaving a first patch containing a different number of hosts and were allowed to visit a second patch containing only kairomones. CO₂ is known to erase unconsolidated information from the memory. We show that in the absence of a short CO₂ narcosis, females responded according to their previous experience, whereas anesthetized females did not. The anesthetized females stayed a given time in the second patch irrespective of what they encountered before. CO₂ narcosis had no effect on the residence time of the non-experienced females in a patch containing hosts or only kairomones in comparison with the non-anesthetized females that had a previous foraging experience. We conclude that CO₂ narcosis erases the effect of the previous patch quality, perhaps due to a memory disruption. Direct information processing is likely to be involved in parasitoid decision making through retention of the information on the previous patch quality into a CO₂ sensitive memory.