Presence and possible function of root effect hemoglobins in fishes lacking functional swim bladders

The adult hemoglobins of 15 species of teleost and the midgestation fetal hemoglobin of the seaperch Embiotoca lateralis show a pronounced decrease in oxygen-carrying capacity at low pH, a Root effect. All of these fishes lack a functional swim bladder, which is generally thought to be the likely site of Root effect hemoglobin function. All of the teleosts examined, including the fetal sea perch, however, have a choroid rete, a structure that is proposed to be involved in oxygen secretion to the eye. The data are inconsistent with the generalization that only fishes with swim bladders possess Root effect hemoglobins, and that the only function of Root effect hemoglobins is in the secretion of oxygen to a swim bladder. The data for the fishes examined in this study suggests that a better correlation may exist between Root effect hemoglobins and the presence of a choroid rete. This is consistent with the hypothesis that Root effect hemoglobins may be involved in the physiology of the eye in many fishes.