The taste system of small fish species.

Small fish species such as the zebrafish (Danio rerio) and medaka fish (Oryzias latipes) are advantageous animal models and have been used as model organisms in many research areas. However, they have not been utilized for studying the taste system, primarily because of a dearth of molecular biological knowledge. Quantitative methods for analyzing the taste preferences of fish species have also been lacking. Recent progress of the fish genome project has enabled the elucidation of the molecular mechanisms of taste sensation. Taste receptors and a number of signal transduction molecules have been identified. Additionally, the development of quantitative methods of feeding using fluorescently labeled artificial foods has demonstrated taste preferences in small fish species. Comparisons between these results in fish and reports on mammals have proposed a general logic and evolution of vertebrate taste systems. Analysis on the transsynaptic tracer-expressing transgenic medaka fish also suggests the usefulness of small fish in the research of neural circuits for taste.