[
International Worm Meeting,
2021]
Sexually dimorphic traits stemming from distinct processing of environmental cues bring about the holistic survival of the species and are mostly driven by sexual selection. However, the underlying mechanisms driving sex-dependent complex decisions remain largely unknown. Previous studies have shown that C. elegans hermaphrodites are able to shift their preference from attraction to aversiveness to a specific pathogenic bacterium Pseudomonas aeruginosa (PA14), after certain hours of exposure (Zhang et al, 2005). Using a modified version of this learned avoidance behavior, we show that C. elegans makes sexually dimorphic choices based on short past experiences. The hermaphrodites learn efficiently, as was previously shown. However, males do not learn to avoid PA14, even after training, thus retaining their initial preference. Using a blind testing paradigm, we show that larval stages of both sexes are unable to shift the preference, suggesting that maturation of nervous system is necessary for short term experience-based plasticity. By performing fast killing assays, we show that the lethality kinetics toward PA14 toxins is similar in the sexes, thus ruling out dimorphic susceptibility. To understand tissue specificity in developing a learned response, tissue specific sex-reversal experiments were performed and the importance of the nervous system was unraveled. In the same vein, we show that short term exposure does not involve signaling from the gut. Previous work has shown the importance of the interneuron AIY within several learning circuits (Ha et al, 2010; Jin et al, 2016). By analyzing AIY synaptic activity using fluorescently labelled RAB-3, we show that, upon short-term exposure, there is a decrease in synaptic activity, specifically, in an axonal region that forms connections with the interneuron RIA (Colon-Ramos et al, 2007). While this trend was prevalent in both the sexes, close examination of Ca2+ fluxes in the same region, using calcium indicators, reveal dimorphic responses to the odor of PA14. These results suggest that downstream encoding of short-term learning is sex-dependent and thus, its neuronal connectivity. To summarize, we present a model in which dimorphic processing of environmental cues, in a sex-specific manner, evokes diverse behavioral phenotypes that help shape the fitness of the species.