MOFFETT, S.B.*; MARTUS, J.M.; GELPERIN, A.: Ablation of a slug’s procerebral lobe blocks its ability to discriminate water sources that are dangerous for rehydration.

Limax maximus, the common garden slug, can experience dramatic reduction in body water and then is highly motivated to find a source of moisture for rehydration through the body surface (Matanock and Welsford,1995). In nature, appropriate sources of moisture often have odors associated with them. Slugs sense odors primarily with their major tentacles, from which information projects into a lobe of the brain called the procerebral lobe. The procerebral lobe has been implicated in odor learning (Teyke and Gelperin,1999). In this experiment, we tested the hypothesis that slugs could be trained to associate odors with water that was unsafe for rehydrating and that this behavior might be missing in slugs that lacked tentacles or the procerebral lobe. We dehydrated slugs and used three trials, spaced over 24 hours, to force them into contact with the dangerous (NaCl- and quinine-added), odor-laden (e.g., orange, cherry, pineapple) water for 2 min. After each dehydration and training exposure, we rehydrated them in an odor free container. In the test situation, 14 of 21 trained control slugs choose to rehydrate on a water source paired with a novel odor rather than in water paired with the odor previously associated with dangerous water. Slugs with the procerebral lobe ablated on one side and the tentacle cut off on the other side behave as if they cannot smell. Of 11 such operated slugs, trained and tested as described above, 7 chose to rehydrate on the water source previously paired with the dangerous water. These data and our behavioral observations suggest that the combination of the unilateral procerebral lobe operation and contralateral sensory ablation can prevent the slugs from learning, perhaps by producing anosmia.