Behavioural and central nervous responses to plant volatiles in Agrotis ipsilon males are mating-independent in contrast to sex pheromone responses.

5. GADENNE C, BARROZO RB, JARRIAULT D, ANTON S.

Congreso; 25th International Society of Chemical Ecology; 2009

We previously showed that male moths of Agrotis ipsilon (Lepidoptera: Noctuidae) are no longer attracted to the female sex pheromone following mating(1). This behavioural plasticity is accompanied by a change in the sensitivity of central olfactory neurons in the macroglomerular complex of the antennal lobe (AL). The loss of sensitivity after mating is restored during the next day(1). This transient neuronal plasticity serves as an energy-saving strategy by switching off the olfactory system and therefore preventing males from mating unsuccessfully. As we previously showed that the central nervous processing of plant odours (in the ordinary glomeruli of the AL) is, contrary to sex pheromone, independent of age (2), we investigated whether the effect of mating on the olfactory system might also be restricted to pheromone processing neurons. We analyzed the behavioural and central nervous responses of virgin and newly mated A. ipsilon males to the sex pheromone blend and a plant odour (linden flower extract/heptanal). By means of wind tunnel experiments, we show that, independently of the dose, the behavioural response to sex pheromone was inhibited after mating. Using intracellular recordings of AL neurons, we show that the sex pheromone starts to be detected above a specific threshold (1ng), which is much higher than in virgin males. On the contrary, both the behavioural and central nervous responses of post-mated males to the plant odour were not different from that of virgin males. By analyzing different parameters of the neuron responses (3), we show that mating changes the central processing of pheromonal information, but not that of plant volatiles. This mating-dependent neuronal plasticity is therefore restricted to the sex-specific pheromonal system and does not affect the responses to general odours such as plant-volatiles.   1. Gadenne et al.  2001. Proceedings Royal Society London B. 268:1631-5. 2. Greiner et al. 2002. Chemical Senses 27:45-48. 3. Jarriault et al. 2009. Journal of Experimental Biology 212:1191-1201.