Influence of sex and time of day on learning and memory in the crab Neohelice granulata.

Fundamental processes for survival, like learning and memory, can be modulated by diverse factors including sex and circadian rhythm. Understanding how these factors shape cognitive processes, and whether their effects are conserved across taxa, represents an important area of research in comparative neuroscience. The crab Neohelice granulata is an established model for unveiling the mechanisms involved in cognitive processes. So far, studies have focused only on males, except for a preliminary study suggesting that females express long-term memory (LTM) but may not retain short-term memory (STM). Recently, we described circadian activity/rest rhythms in this species, showing high locomotor spontaneous activity during night and crepuscular hours, and a prolonged resting phase at midday/afternoon. This project aims to integrate the effect of circadian rhythmicity and sex on learning and memory in N. granulata. Using a well-established Contextual Pavlovian Conditioning protocol, involving repeated spaced presentations of a visual danger stimulus, we studied learning and memory in male and female crabs trained at either active (early morning) or resting (early afternoon) phases of the day. Our analysis includes comparisons between groups regarding exploratory activity, initial stimulus response, acquisition rate, and either STM (4 h) or LTM (24 h) retention. This approach contributes to identifying sources of variation in learning and memory processes in N. granulata.