The occurrence of argyrophilic and argentaffin cells in the gut of Ciona intestinalis L

Immunocytochemical localization of serotonin in embryos, larvae and adults of the lancelet, Branchiostoma floridae

Serotonin (5-hydroxytryptamine) is a biogenic amine distributed throughout the metazoans and has an old evolutionary history. It is involved as a developmental signal in the early morphogenesis of both invertebrates and vertebrates, whereas in adults it acts mainly as a neurotransmitter and gastrointestinal hormone. In vertebrates, serotonin regulates the morphogenesis of the central nervous system and the specification of serotonergic as well as dopaminergic neurons. The present study uses, as an experimental model, an invertebrate chordate, the lancelet Branchiostomafloridae, characterized by its remarkable homologies with vertebrates that allows the 'bauplan' of the probable ancestor of vertebrates to be outlined. In particular, the involvement of serotonin as a developmental signal in embryos and larvae, as well as a neurotransmitter and gastrointestinal hormone in adult specimens of Branchiostoma floridae, gives further support to a common origin of cephalocordates and vertebrates.

Localization of immunoreactive gastrin-like cells in the alimentary tract of the ascidian Styela plicata

The occurrence of a gastrin-like immunoreactivity in the alimentary tract of the ascidian Styela plicata has been investigated using immunocytochemical methods. Gastrin-like cells are present only in the gastric epithelium among the cell types responsible for digestion and absorption of food. The physiological role played by the ascidian gastrin-like peptides is discussed together with the evolutionary history of peptides of the gastrin/cholecystokinin family.