Epsilon Open Archive

Abstract

In order to respond appropriately to external stimuli, e.g. odours in the environment,insects have to evaluate these stimuli in a context of relevance and need. These decisions are, in turn, based on internal physiological status, such as mating status.
In the cotton leafworm, Spodoptera littoralis, mating induces profound physiological changes that alter the behavioural output to fit with the current needs of the animal. In female S. littoralis, mating switches the behavioural attraction from food sources to oviposition sites and concurrently down- and up-regulates olfactory neuron sensitivity. This switch in olfactory sensitivity is correlated with a transient increase in dopamine levels in the primary olfactory brain centres, the antennal lobes.
In male S. littoralis, mating induces a transient behavioural and olfactory inhibition towards female-emitted sex pheromone as well as to mating site-related odours. However, responses towards food sources remain constant. The shift in olfactory responsiveness is not correlated with changes in dopamine levels, but may be regulated by neuropeptides expressed in the olfactory system. Distribution patterns of 6 of the most abundant neuropeptides reveal distinct differential expressions within the antennal lobe glomerular array, providing the possibility for selective and state-dependent modulation of the olfactory system.