I previously introduced the worm Ceanorabditis elegans (C. elegans) (« Une histoire de ver et d’ultrasons »), underlining the fact that every connexions and cells of its nervous system were known…Well, every statement in science is susceptible to change. A study published in Nature revealed the existence of two extra neurons in C. elegans. Interestingly, they are only observed in male nematode worms… Here starts the story.
C. elegans is a sexually dimorphic species with hermaphrodites and males. The first can self-fertilize whereas the second can only cross-fertilize hermaphrodites. There is a marked dimorphism of behaviours between hermaphrodites and males, both reproductive and non-reproductive. Only males perform sexual conditioning : they need to learn how to optimally locate mating partners. This is a form of associative learning whereby males use sodium chloride as a cue for hermaphrodite location. Both males and hermaphrodites normally avoid sodium chloride after associative conditioning with salt and starvation. However, males become attracted to sodium chloride after conditioning with salt and starvation if hermaphrodites are present during conditioning. This contrasting behaviour of male and hermaphrodite is linked to differences in brain development and structure in areas involved in higher order processing.
The authors of the study lead by Dr Arantza Barrios, from University College London, discovered a previously unknown pair of neurons in the head of males, which they have called MCMs (for mystery cells of the male). They proved that these two cells, which they identified as interneurons arising from glial cells, are specifically required for a male-specific switch in chemosensitory behaviour induced by sexual conditioning. “We’ve shown how genetic and developmental differences between the two sexes lead to structural changes in the brain of male worms during sexual maturation. These changes make male brains work differently, allowing males to remember previous sexual encounters and prioritise sex in future situations.”
According to Arantza Barrios: “Areas of the brain involved in learning display sex differences in many animals, including humans, but how these differences directly affect behaviour is not clear. » It is tricky to extrapolate these results to other species. But it’s a foundation stone in building the understanding of these mechanisms.
Glia-derived neurons are required for sex-specific learning in C. elegans. Sammut M. et al, Nature 15 october 2015.
http://www.nature.com/nature/journal/v526/n7573/full/nature15700.html
http://www.ucl.ac.uk/cdb/academics/arantza_barrios
https://www.ucl.ac.uk/biosciences/biosciences-news-publication/poole_barrios
Ricochets 
Il semble que les suggestions du Pr Barrios et autres chercheurs permettent d’affirmer l’existence de MCM (mysterious cells of the male) dans l’espèce particulière étudiée. Ceci ouvre un espace de recherches intéressant sur les possibilités de penser que, en dehors du champ restreint des vers Caenorhabiditis ‘(C.) elegans, il pourrait y avoir, dans d’autres espèces plus complexes, des explications dues à la présence de neurones différents suivant les sexes intervenant pour définir une attitude, des préférences, des aptitudes voire des jugements. Les études ne négligent pas le côté incertain de l’expérience et gardent la possibilité d’expliquer en partie les faveurs accordées par chaque sexe à telle ou telle priorité ou attitude par une donnée comportementale.Les données scientifiques étant par nature elles susceptibles de change pour pouvoir changement nous attendons d’autres études notamment sur la différence biologique ou comportementale enter l’individu non attiré par la mobilité et la personne susceptible de favoriser celle-ci dans ses choix comportementaux. Bien entendu le croisement de cette donnée avec des variables dues à l’heure de l’exercice, au jour de celui-ci ou à l’origine socio-économique des éléments de la cohorte devront être croisés avec les premiers résultats.
Ch. P