Palatability of Bile Substances for Fish

Abstract

Palatability of sodium cholate (10^–1 M), sodium taurocholate (10^–1 M), and dehydrocholic acid (0.5 × 10^–3 M) for Mexican cavefish Astyanax fasciatus (blind form), silver dollar Metynnis argenteus, Nile tilapia Oreochromis niloticus, green swordtail Xiphophorus hellerii, and roach Rutilus rutilus was assessed. All substances have a significant taste effect, but the reaction of fishes to their taste is different and the responses to the same substance were different. Taste attractiveness for bile substances (sodium taurocholate, dehydrocholic acid) was found only in Mexican cavefish, which allows it to feed on specific food (bat guano) available in cave reservoirs where other food resources are extremely insignificant. For the rest of the fishes, bile substances had an inert or aversive taste, which can prevent coprophagy and contribute to long-term preservation of feces in the environment, which are an important source of odor signals for fish. It has been proposed to consider bile substances as important chemical regulators of fish relationships in aquatic communities.