Lymnaea: A genus of dextrally coiled freshwater snails that includes some species of importance as intermediate hosts of parasitic flukes.FMRFamide: A molluscan neuroactive peptide which induces a fast excitatory depolarizing response due to direct activation of amiloride-sensitive SODIUM CHANNELS. (From Nature 1995; 378(6558): 730-3)Snails: Marine, freshwater, or terrestrial mollusks of the class Gastropoda. Most have an enclosing spiral shell, and several genera harbor parasites pathogenic to man.Memory, Long-Term: Remembrance of information from 3 or more years previously.Ganglia, Invertebrate: Clusters of neuronal cell bodies in invertebrates. Invertebrate ganglia may also contain neuronal processes and non-neuronal supporting cells. Many invertebrate ganglia are favorable subjects for research because they have small numbers of functional neuronal types which can be identified from one animal to another.Molluscacides: Agents destructive to snails and other mollusks.Invertebrate Hormones: Hormones produced by invertebrates, usually insects, mollusks, annelids, and helminths.Respiratory Physiological Processes: Biological actions and events that support the functions of the RESPIRATORY SYSTEM.Fasciola hepatica: A species of helminth commonly called the sheep liver fluke. It occurs in the biliary passages, liver, and gallbladder during various stages of development. Snails and aquatic vegetation are the intermediate hosts. Occasionally seen in man, it is most common in sheep and cattle.Paramphistomatidae: A family of flukes of the class Trematoda found in the intestinal tract and liver of animals and man. Some of the genera are Homalagaster, Gastrodiscus, Paramphistomum, Watsonius, Nilocotyle, Gigantocotyle, Gastrothylax, Macropotrema, Ceylonocotyle, Zygocotyle, Cotylophoron, and Calicophoron.Fascioliasis: Liver disease caused by infections with parasitic flukes of the genus FASCIOLA, such as FASCIOLA HEPATICA.Fasciola: A genus of trematode liver flukes of the family Fasciolidae. Two species of this genus are F. hepatica and F. gigantica. The parasites are found in the liver and gallbladder and associated ducts in mammals and occasionally man. F. gigantica occurs rarely in man.