LLove makes you blind, as we all know. Blind to the reality of the loved one, that is. We would almost apologize for making such a clarification. However, a study published on Wednesday, August 28 in the journal Nature invites us to consider the expression in a completely different way. In an experiment carried out on fruit flies, a team from the University of Birmingham has just shown that during courtship males become insensitive to visual cues of the presence of a predator.
It must be said that among animals, staying alive and reproducing, two of the very goals of their existence, often prove to be contradictory. From hamsters forced to leave their burrows to find a partner to birds overflowing with shimmering colors to seduce their beloved, at the risk in both cases of being spotted by their predator, the trade-off between threat and gain is imposed on many species. Humans included. “But how does the brain evaluate danger and reward to make the best possible decision? We know little about it.”says Carolina Rezaval, a neurogeneticist at the University of Birmingham and coordinator of the study.
To address this general question, British researchers looked at the fruit fly, or drosophila, a favorite of the lab for decades. Every corner of its genome has been explored. Males also have the advantage of practicing a particularly stereotypical seduction ritual: the courtier first turns toward the object of his desire, pursues it, taps its abdomen to detect pheromones, then begins a serenade by vibrating its wings. Finally, as the last stage before acting, he folds his abdomen. Could this sequence have set the rhythm for the perception of danger in young Don Juans?
Action of dopamine
The Birmingham team therefore designed an artificial threat, a sort of predator made of shadow and light. “Normally, fruit flies react by fleeing or remaining immobile.”describes Carolina Rezaval. In the brain, One of the main messengers is serotonin. Sometimes called the “happiness hormone” in humans, it controls specific neurons associated with stress and fear in flies. This has been verified and detailed using optogenetics, a technique that allows a neuron to be activated or inhibited by a flash of light.
It was still necessary to be able to follow the phenomenon throughout the entire duration of the courtship. By opening a tiny window in the males’ cranium, the scientists were able to observe in real time, under a microscope, the reaction of the neurons to the presentation of the threatening shadow. With a spectacular result: during the first stages, the male remains receptive to danger. But, once he folds his abdomen, nothing else matters. “His brain is so focused on reproduction that it overrides the survival instinct, insists Carolina Rezaval. The strength with which dopamine then blocks the perception of danger really surprised us.”
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