Amino acid-induced reflexes and their neural pathways in an opisthobranch mollusc Pleurobranchaea japonica

Certain behavioral acts of Pleurobranchaea japonica may be elicited in resp onse to chemical stimulants applied to the rhinophores, tentacles or oral v eil. These include feeding and escape. Upon treatment with chemical stimula nts, the organs respond directly by extending or withdrawing. Beyond this, aversive responses involved withdrawal of the rhinophores, tentacles and or al veil plus contraction of the whole body. Feeding behavior was elicited b y glycine, phenylalanine, proline, aspartic acid, alanine, asparagine, tryp tophan and glutamine. An aversive response was induced by glutamate. Neural pathways responsible for these chemoreceptive reflexes have been identifie d. In addition to known nerves, a newly identified pair of nerves, the seco nd pedal nerves arise from the pedal ganglion and send branches to the thre e organs. The nerves contain afferent pathways for chemoreception of the or gans and efferent motor pathways for the movements of the organs. The rhino phore ganglion is responsible for the glutamate-induced contraction of the rhinophore. This withdrawal reflex of the rhinophore is under inhibitory co ntrol, exerted by the cerebral ganglion through the rhinophore nerve, and u nder an excitatory influence, emanating from the pedal ganglion through the second pedal nerve.