Can sharks taste bitter substances?

Researchers have discovered a receptor for bitter taste in twelve different cartilaginous fish (sharks and rays). The receptor belongs to the so-called taste receptors type 2 (T2R), which also makes humans perceive bitter and potentially toxic foods. Until now, it was assumed that such receptors only occur in bony vertebrates. Twelve out of 17 cartilaginous fish genomes studied contained genes for the taste receptors type 2, with only one T2R gene present in each species (Proceedings of the National Academy of Sciences). The researchers named this single gene T2R1. The fact that only a single T2R gene was found suggests that it is the original form of these bitter taste receptors, which was not altered by gene duplication and subsequent different specialisation of the resulting receptors. The results showed that both bamboo shark and the catshark can taste bitter substances also perceived by humans, such as colchicine or bile acid. A screening of ninety-four human bitter substances identified eleven substances that could also activate the sharks’ receptors.