FMRFamide-like Immunoreactivity in the Nervous System of the StarfishAsterias rubens

Abstract

The nervous system of the starfish Asterias rubens was subjected to immunocytochemical investigation using antisera raised against the molluscan neuropeptide FMRFamide. Immunoreactivity was detected in the radial nerve cords and the circumoral nerve ring, as well as in the sub-epithelial nerve plexus of the tube foot system. The hyponeural part of the radial cords contained numerous immunoreactive cell bodies. In the ectoneural tissue, immunoreactive cells were present in the epithelium, with cell bodies especially abundant in the lateral parts of the nerve, close to the site of emergence of the innervation to the tube feet. The sub-epithelial nerve plexus of the tube feet contained immunoreactive fibers that were continuous with an extensive system of ectoneural immunoreactive fibers in the radial nerve cords. Immunoreactive fibers were particularly evident in the regenerating radial nerves of previously sectioned arms.