STRUCTURE OF THE NERVOUS SYSTEM OF THE AURICULARIA LARVA OF PARASTICOPUS CALIFORNICUS

¹ Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 2Y2

The structure and organization of the larval nervous system of the holothurian, Parasticopus californicus, is described using glyoxylic acid-induced fluorescence, indirect immunofluorescence with antibodies against serotonin, and transmission and scanning electron microscopy. Tracts of catecholaminergic axons are located at the base of the ciliary bands and catecholaminergic nerve cell bodies are dispersed along the length of the ciliary bands. Clusters of catecholaminergic cells form a ganglion on the lower lip of the larva and a ganglion of serotonergic cells is located at the anterior tip of the larva. Serotonergic cells are scattered throughout the apical portion of the larva in the epidermis. Axon tracts identified only with TEM are located in the esophagus associated with the circumesophageal muscles. The neuroanatomy of the auricularia shares several features with larval forms of the other classes of echinoderms.