Aquaporin (Aqp) 10 water channels in humans allow the free passage of water, glycerol, urea, and boric acid across cells. However, Aqp10.2b in pufferfishes allows only the passage of water and glycerol and not urea and boric acid. Researchers sought to understand the evolutionary timeline that resulted in the variable substrate selection mechanisms among Aqp10s. Their results indicate that Aqp10.2 in ray-finned fishes may have reduced or lost urea and boric acid permeabilities through evolution.