A Neuroplastic Network Underlying Behaviour and Seasonal Change in Lymnaea stagnalis: A Neuroecological Standpoint

The gastropod mollusc Lymnaea stagnalis (L.) is an advantageous model system for neureothological studies and is a suitable model for studying Neuroecology. Here we describe its well organised nervous system many of whose ganglia have been mapped, both electrophysiologically and morphologically, to characterise individual giant neurons and neuronal clusters. This has allowed us to speculate on the evolution and reorganisation of the brain in relation to torsion and detorsion and to show that many behavioural networks remain virtually intact during these processes, but reflect the evolutionary changes that the nervous system has undergone in adaptation of the animal to its environment. We also describe the Lymnaea behavioural hierarchy in which the defensive whole body withdrawal reflex takes precedence over all other behaviours, all of which appear to be organised on a multiganglionic basis and underlain by a complex neural network in which several central pattern generators (CPGs) are embedded. The interactions of the CPGs with one another and with a number of wide-acting synaptic inputs are discussed with particular reference to the locomotor and respiratory systems of the animal. Knowledge of these cellular interactions has allowed us to demonstrate seasonal changes within the respiratory CPG (RCPG) of Lymnaea with a loss of connectivity as winter approaches and a restoration of synaptic connectivity and the behavioural programme during the spring. With its flexible and adaptable behavioural repertoire Lymnaea is well adapted to its freshwater environment. We suggest that it will prove to be a useful and sensitive model for studying the neuroecological effects of climate change with particular respect to invasive freshwater species (IFS) such as predators, freshwater plans or microbial species.