Immunofluorescent localisation of somatostatin-like cells in the esophagus of a protochordate

By means of the indirect immunofluorescence method, somatostatin-like immunoreactive (SLI) cells are detected in the esophagus of the ascidian Styela plicata. They are of the "open" type; they act probably by a paracrine mechanism on the esophageal secretin-like cells. The ascidian SLI cells are negative to all the specific cytochemical methods characteristic of vertebrate somatostatin (D) cells, which were applied in this work. In consequence, special SLI cells are probably present in ascidians.