Context-dependent effects of social isolation and behavioural recovery in two populations of Lymnaea stagnalis.

Social context is a key modulator of behaviour and cognition across taxa, yet the effects of social isolation (SI) and subsequent recovery remain poorly characterised in invertebrate systems. Here, we developed a longitudinal behavioural procedure to examine how SI and social reintroduction (SR) influence feeding, exploration, and operant conditioning behavioural assays in the pond snail Lymnaea stagnalis. To capture biologically relevant variation, we compared two populations with differing environmental backgrounds: a long-established laboratory strain (W) and a "wild" population (TC1). Isolation was associated with reproducible changes across multiple behavioural domains, including reduced feeding and impaired memory performance in an operant conditioning assay. These effects emerged more rapidly in laboratory-inbred snails, whereas the "wild" ones required a longer isolation period to exhibit comparable behavioural alterations, indicating differences in response dynamics between populations with distinct environmental backgrounds. Following SR, behavioural recovery was modulated by social context. In W snails, social reintroduction with familiar conspecifics was associated with substantial recovery, whereas social reintroduction with unfamiliar conspecifics produced more limited improvement. In contrast, TC1 snails showed a delayed onset of behavioural disruption and less complete recovery after social reintroduction within the tested Timeframe, irrespective of conspecific familiarity. Together, these findings demonstrate that responses to social isolation in L. stagnalis are strongly influenced by population background and the social environment during recovery. By integrating laboratory-reared and "wild" populations within a multi-behavioural approach, this study establishes a tractable framework for future investigations linking social context to the neural and molecular mechanisms underlying behaviour and learning.