Fig. 3. Learning and memory of snails trained in 50 and 75 µmol l^–1 of H₂S. (A) A cohort of naïve snails (N=24) were trained using the same LTM training procedure as in Fig. 2 while being exposed to H₂S at a concentration of 50 µmol l^–1. This cohort of snails showed both learning and memory (ANOVA F_(23,2)=23.9962 P<0.01; sessions 2 and 3 significantly different from session 1, P<0.01). (B) Another cohort of naïve snails (N=11) was subjected to the same LTM training procedure as in A except that these snails were exposed to an H₂S concentration of 75 µmol l^–1. Again both learning and memory occurred (ANOVA F_(10,2)=6.6139, P<0.01; sessions 2 and 3 significantly different from session 1, P<0.05 and P<0.01, respectively).