Physiological significance of Root effect hemoglobins in trout

Root effect hemoglobins are found in trout and salmon. These functionally unique hemoglobins are believed to be intricately involved in oxygen secretion to the swimbladders of many fishes. This has also been proposed as their primary physiological role in trout; however, such an oxygen secretory function is unlikely in these fish. Trout swimbladders characteristically contain very high concentrations of nitrogen and the anatomical structures associated with swimbladder gas secretion are absent from trout. Also, trout appear to fill their swimbladders by physical deposition of gas, with the following of surface air, rather than by chemical secretion, thus obviating a role of Root effect hemoglobins at the swimbladder. A chemical secretion of gas is likely involved in oxygen secretion to the eye. The eyes of trout, as those of many fishes, contain very high concentrations of oxygen which exceed those found in the blood or ambient water. Data are consistent with a physiological role of trout Root effect hemoglobins in oxygen secretion to the eye; they are not consistent with a role in any gaseous secretion to the swimbladder.