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Males and females are evolutionarily programmed differently in terms of sex

Regardless of sharing a very similar genome and nervous system, males and females vary significantly in reproductive investments. They require different behavioral, morphological, and physiological adaptions, suggests a new study from Oxford, which found sex-specific signals affect behavior.

As the study suggested, Males and females behave differently in terms of sex, but the reality is both are evolutionarily programmed to do so. They both have evolved profoundly different adaptations to suit their own reproductive needs.

In their study, scientists uncovered a novel circuit architecture principle that permits deployment of entirely behavioral repertoires in males and females, with minimal circuit changes.

Scientists found that the nervous system of vinegar flies, Drosophila melanogaster, produced differences in behavior by delivering different information to the sexes.

In the vinegar fly, males compete for a mate through courtship displays; thus, the ability to chase other flies is adaptive to males but of little use. A female’s investment is focused on the success of their offspring; thus, choosing the best sites to lay eggs is adaptive to females.

While discovering the different roles of only four neurons clustered in pairs in each hemisphere of the central brain of both male and female flies, scientists detected sex differences in their neuronal connectivity. This neuronal connectivity reconfigures circuit logic in a sex-specific manner.

In essence, males received visual inputs and females received primarily olfactory (odor) inputs. Notably, the team demonstrated that this dimorphism leads to sex-specific behavioral roles for these neurons: visually guided courtship pursuit in males and communal egg-laying in females.

Scientists noted, “Ultimately, these circuit reconfigurations lead to the same result—an increase in reproductive success.”

“Our findings suggest a flexible strategy used to structure the nervous system, where relatively minor modifications in neuronal networks allow each sex to react to their surroundings in a sex-appropriate manner.”

Professor Stephen Goodwin from the Department of Physiology, Anatomy, and Genetics said, “Previous high-profile papers in the field have suggested that sex-specific differences in higher-order processing of sensory information could lead to sex-specific behaviors; however, those experiments remained exclusively at the level of differences in neuroanatomy and physiology without any demonstrable link to behavior. I think we have gone further as we have linked higher-order sexually dimorphic anatomical inputs, with sex-specific physiology and sex-specific behavioral roles.”

Scientists noted, “In this study, we have shown how a sex-specific switch between visual and olfactory inputs underlies adaptive sex differences in behavior and provides insight on how similar mechanisms may be implemented in the brains of other sexually-dimorphic species.”

Journal Reference:
  1. Tetsuya Nojima et al. A sex-specific switch between visual and olfactory inputs underlies adaptive sex differences in behavior. DOI: 10.1016/j.cub.2020.12.047

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