ABSTRACT
The pond snail, Lymnaea stagnalis, is a model molluscan system used in many laboratories to study a wide range of biological problems. The snails are widely distributed throughout Europe, the Northern parts of the United States and parts of Asia in freshwater ponds, lakes, and rivers with rich vegetation. Multidisciplinary endocrinological, electrophysiological, and molecular approaches on Lymnaea have led to a deep understanding of peptide-mediated neurohormonal and neuromodulatory mechanisms underlying physiology and behavior. Peptidergic control of heartbeat is the best-understood example of the modulatory control of a rhythmically active muscular organ by extrinsic peptide-containing neurons. The range of general roles that peptides play as transmitters and co-transmitters are exemplified by results from the heart control system. The end of these courtship behaviors and the start of the copulation phase are characterized by the intromission of the penis into the female gonopore.
