The influence of host site experience on subsequent flight behaviour in Microplitis croceipes (Cresson) (Hymenoptera: Braconidae)

The effect of selected experiences on subsequent flight behavior by the parasitoid Microplitis croceipes, after its arrival at a potential host site, was examined in a flight tunnel. Exposing M. croceipes to host frass from Helicoverpa zea (Boddie) larvae fed fresh cowpea leaves reinforced its sustained flight response to a hexane extract of that same frass, while an exposure to host frass followed by an oviposition reduced subsequent sustained flight responses to the hexane extract. When oviposition experience was given to M. croceipes outside its target area, or when host site appearance was changed after oviposition, no reduction in sustained flight responses was found. Our results suggest that M. croceipes is able to associatively learn the site of oviposition by linking oviposition experiences to spatial information, thereby reducing the frequency of revisitation and self-superparasitism. The ecological significance of these results is discussed.

A learning-related variation in electroantennogram responses of a parasitic wasp

Odour responses of parasitic insects, in search of their hosts, can change due to experience. Leptopilina heterotoma (Thomson) (Hymenoptera; Eucoilidae), a parasitic wasp of drosophilid larvae, is known to alter its preference for odours emanating from host food substrates through learning. These kinds of behavioural modifications in insects are assumed to be the result of complex processes in the brain. The results presented in this report, however, suggest that this learning-related behavioural variation is not restricted to brain processes but that it involves changes in sensitivity of olfactory receptor neurones.

No association between striatal dopamine transporter binding and body mass index: A multi-center European study in healthy volunteers

INTRODUCTION: Dopamine is one among several neurotransmitters that regulate food intake and overeating. Thus, it has been linked to the pathophysiology of obesity and high body mass index (BMI). Striatal dopamine D(2) receptor availability is lower in obesity and there are indications that striatal dopamine transporter (DAT) availability is also decreased. In this study, we tested whether BMI and striatal DAT availability are associated. METHODS: The study included 123 healthy individuals from a large European multi-center database. They had a BMI range of 18.2-41.1 kg/m(2) and were scanned using [(123)I]FP-CIT SPECT imaging. Scans were analyzed with both region-of-interest and voxel-based analysis to determine the binding potential for DAT availability in the caudate nucleus and putamen. A direct relation between BMI and DAT availability was assessed and groups with high and low BMI were compared for DAT availability. RESULTS: No association between BMI and striatal DAT availability was found. CONCLUSION: The lack of an association between BMI and striatal DAT availability suggests that the regulation of striatal synaptic dopamine levels by DAT plays no or a limited role in the pathophysiology of overweight and obesity