ABSTRACT
The digestive system of ophiuroids is undoubtedly the simplest among echinoderms. Ophiuroids have blind guts with the mouth always situated mid-ventrally and more or less hidden by a jaw apparatus located just below. Published data pertain mainly to species belonging to the order Ophiurida. The stomach consists of a relatively flat central area and ten peripheral pouches. The digestive wall consists basically of three tissue layers: the digestive epithelium, a connective tissue layer, and a muscular mesothelium. A basi-epithelial nerve plexus is associated with the digestive epithelium and is conspicuous mainly in the esophagus. Peripheral tissues are welldeveloped in the esophageal wall, but are remarkably thin in the stomach wall where they have a total thickness of times less than that of the digestive epithelium. The main secretory areas are the entrances to the interradial pouches where granular secretory cells and mucus cells are present in great number. The gut of ophiuroids is poorly investigated and comparative data are lacking.
