Learned olfactory discrimination versus innate taste responses to amino acids in channel catfish (Ictalurus punctatus).

Intact channel catfish conditioned to the L-amino acids, proline, arginine, alanine, and lysine, discriminated these stimuli from all other amino acids tested. Behavioral structure-activity tests indicated that L-pipecolate was the only effective agonist of the L-proline conditioned response. For channel catfish in which one of the paired olfactory organs was surgically removed, the number of turns to the conditioned stimulus was 40% fewer than those of intact catfish; however, these semiosmic channel catfish discriminated the conditioned from nonconditioned stimuli, as evidenced by their responding to the conditioned amino acid, with a two- to threefold greater number of turns than to the nonconditioned amino acids. Irrespective of the number of conditioning trials attempted, catfish with both olfactory organs removed were unable to discriminate the conditioned from the nonconditioned stimuli.