Evidence of conditioned food aversion in Japanese fire-bellied newts (Cynops pyrrhogaster)

Paradis and Cabanac (2004) reported that amphibians, such as toads and newts, do not exhibit a decrease in consumption of a food conditioned stimulus (CS) after being paired with an injection of LiCl. Although they described the food CS as completely novel to the animals, we hypothesized that prior experience with other foods may have generalized to the food CS, leading to stimulus generalization of latent inhibition and impairing the acquisition of a conditioned food aversion. Our aim was to examine conditioned food aversion in Japanese fire-bellied newts (Cynops pyrrhogaster) using a food CS that was expected to be novel in flavor to the subjects. We used kamaboko, a Japanese processed food made from pureed fish with added salt and other ingredients. Newts in the experimental groups received an injection of either 190 mg/kg or 285 mg/kg of 0.15 M LiCl immediately after presentation of the food CS, while the control group received an injection of the same dose of saline. Compared to the control group, both experimental groups exhibited a significant reduction in consumption of the food CS during the test. In contrast, in an additional test conducted on the day following the CS presentation test, no significant differences were found among the groups in their consumption of the familiar food pellets that they had been consuming prior to the experiment. These results suggest that Japanese fire-bellied newts can acquire a conditioned food aversion.