Sensory Enrichment and Deprivation During Development: Limited Effects on the Volumes of CNS Neuropils in Two Spiders With Different Ecology.

Neuroplasticity is a core property of animal nervous systems, enabling structural changes in the brain in response to environmental stimuli or internal processes such as learning. Among spiders-a diverse group of predators-neuroanatomy varies with hunting strategy: stationary species that build capture webs differ from cursorial species that hunt without webs, reflecting reliance on distinct sensory modalities. While neuroplasticity has been documented in cursorial jumping spiders, its direct drivers remain unclear. In this study, we tested how sensory input influences the central nervous system (CNS) and whether stationary and cursorial hunters differ in their plastic responses. Using sensory deprivation and enrichment, we reared spiders under four treatments: control (CON), vibratory enrichment (VIB), visual enrichment (VIS), and combined enrichment (VISVIB). We examined the stationary hunter Parasteatoda tepidariorum and the cursorial hunter Marpissa muscosa. We predicted that enrichment would enlarge neuropil volumes in modality-specific brain regions, with stronger vibratory effects in P. tepidariorum and stronger visual effects in M. muscosa. Contrary to our expectations, sensory enrichment did not increase the volume of the corresponding CNS neuropils in either species. Although certain neuropils showed significant differences in specific groups, no clear causal link to sensory input emerged. Instead, a substantial proportion of the variation in neuropil volume was explained by family effects (shared maternal origin). We discuss these findings in the context of potential mechanisms underlying environmental plasticity in the spider brain.