Immunohistochemical localization of bioactive substances in the epidermis of the earthworm, Lumbricus terrestris (Annelida, oligochaeta)

Serotonin (5HT), endothelin-big (ET-big) and neuron-specific enolase (NSE) are present in some epithelial paraneuronal cells of vertebrates. In the in vertebrates, we show for the first time, by immunofluorescence and immunope roxidase methods, the immunoreactions to antibodies raised to ET, 5-HT and NSE in the epidermis of the Lumbricus terrestris. It is assumed that the re active cells are small granular cells that may have a paracrine action in t he mechanisms of cell proliferation and secretory processes. The function o f these bioactive substances in the epidermis of the earthworm awaits inves tigation. Phylogenetically it is very interesting that paraneuronal-like ty pe of cells appear in such an ancient species of invertebrate which uses th e epidermis for various functional activities.