The Physiology of Taste in Fish: Potential Implications for Feeding Stimulation and Gut Chemical Sensing

Recent advances in understanding the molecular basis of taste physiology in fish could open new opportunities to optimize feeding performance in aquaculture. This is particularly relevant at a time when alternative ingredients are being increasingly used, often reducing the digestibility and acceptability of fish diets, even if they are nutritionally balanced. The molecular characterization of fish taste receptors T1Rs and T2Rs revealed common taste discrimination mechanisms among vertebrates. In addition, data so far appear to indicate that taste signaling elements are conserved from fish to mammals. Nevertheless, fundamental differences between ligand specificities of taste receptors, and the presence of multiple T1R2s in fish species, underlines evolutionary adaptations of the T1R2 receptor to sense metabolically important nutrients, with a shift from sugars in mammals to amino acids in teleosts. This fits well with electrophysiological and behavioral studies on ligand specificities and taste preferences in several fish species. On the other hand, synergistic responses between different attractants could result from additive effects of independent receptor sites and response mechanisms, and this knowledge can be of practical interest to specifically design stimulant mixtures to modulate feed intake in aquaculture. Mammalian taste receptors and signaling elements have also been identified in the gastrointestinal tract, where they trigger multiple endocrine and neuronal pathways regulating digestion, nutrient absorption, feeding, and metabolism. Evidence for the existence of these receptors and signaling pathways in fish guts have recently been uncovered, suggesting that sensory properties of the diet might also have functional effects beyond oral taste sensations and palatability.