In the complex network of biological interactions that define the rhythm of nature, researchers from the National Research Institute for Agriculture, Food and the Environment (INRAE), in France, bring to light discoveries about how sociosexual interactions can profoundly influence the circadian rhythm in animals . This paves the way for new strategies in agricultural pest control and advances in understanding the underlying biological mechanisms.
The study focused on Spodoptera littoralis, a solitary insect by nature, but whose sociosexual interactions play a crucial role in its reproduction. This insect is known to be a significant agricultural pest, with its larvae attacking corn and legume crops. The intriguing thing is that males, who only live 7 to 8 days, dedicate themselves entirely to procreation, making interactions with females an absolute priority.
Researchers observed that, in the presence of females, the circadian rhythm of males S. littoralis is changed significantly. Females can remotely modulate the circadian rhythm of males through pheromones, specifically the compound (Z,E)-9,11-tetradecadienyl acetate (Z9E11-14Ac), ensuring that both sexes are in sync during the mating period . According to the researchers, the discovery is pioneering, marking the first time that a sociosexual interaction has been shown to affect the circadian clock in a solitary species, even surpassing the influence of light in the process.
The applicability of these findings to biocontrol practice is particularly promising. Researchers are exploring ways to use the modulation of the circadian rhythm of males to desynchronize the reproductive cycles of the sexes, interfering with the meeting between males and females and, consequently, the reproduction of the pest. Such an approach could offer a more sustainable pest control strategy that is less dependent on chemical pesticides.
The article published by the researchers has the following summary:
"To derive any adaptive benefit, the circadian clock needs to be synchronized with the 24-hour day-night cycles. We investigated whether it is a general property of the brain's circadian clock to recognize social interactions as external generators of time. Sociosexual interactions with the opposite sex are universal, prevalent even in the lives of solitary animals.
The moth's lonely adult life Spodoptera littoralis is singularly dedicated to sex, offering an ideal context for exploring the impact of sociosexual cues on circadian timing. We identify specific olfactory cues responsible for social entrainment, revealing a surprisingly strong influence of remote pheromone-mediated sociosexual interactions on circadian rhythms. The free-running rhythms of males are induced and synchronized by the sex pheromone that the female releases rhythmically, highlighting a hierarchical relationship between female and male circadian oscillators. Even a single pulse of the sex pheromone altered the expression of the clock gene in the male brain, overcoming the effect of light on the clock.
Our finding of a long-lasting, day-dependent impact of pheromone on male courtship effectiveness indicates that circadian timing in moths is a feature of sexual selection. We identified specific components of the sex pheromone mixture that do not possess mate-attracting properties but have powerful circadian effects, providing justification for their continued retention by the female. We show that such volatiles, when shared between sympatric moth species, can trigger communal synchronization. Our results suggest that the sex pheromone released by female moths follows the rhythm of male behavioral activity to ensure mating synchrony."
More information at doi.org/10.1016/j.cub.2024.02.042
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