[The localization and functional status of serotonin-producing structures in the gastrointestinal tract of chum salmon fry].

The data obtained shows that serotoninergic structures of the juvenile Siberian salmon gastrointestinal tract involve individual goblet cells of the mucose epithelium, serotoninergic cells as the components of the stomach cardiac glands, fibre-like structures in subepithelial and muscular layers related, probably, to a neural plexus. The serotoninergic structures decrease in their number towards the distal portion of the tract.