The Withdrawal Response of a Freshwater Snail (Lymnaea Stagnalis L.)

Abstract

1. Electrical stimulation of a variety of nerves towards the brain results in movements of the neck of the snail similar to those associated with the withdrawal response of the intact animal. 2. The columellar and cervical nerves mediate most of the movements being measured. 3. Repetition of the stimuli results in a decline in response amplitude which is complicated by a superimposed incremental process which is itself subject to a decremental process as stimuli are repeated. 4. As stimuli are repeated the response latency increases. 5. Consecutive stimulation of pairs of nerves indicates that the response decrement is specific to the nerve being stimulated. 6. The involvement of the pleuro-pedal connectives in the response has been demonstrated both in a semi-intact preparation stimulated electrically and in a free-roaming animal treated surgically and stimulated visually. 7. Visual stimuli associated with the withdrawal response are detected by photoreceptors on the head and in the mantle.