The role of blood pigments in the delivery of oxygen to tissues

Abstract

1. The detailed manner in which the blood respiratory pigments of many invertebrates function is not well understood. 2. The hemocyanins of the cephalopods studied appear to function in gas transport much like the hemoglobins of the vertebrates although these hemocyanins possess a much larger Bohr effect. 3. The properties of the hemocyanins of the crustacea are fairly uniform but those of the mollusca vary considerably. 4. The hemocyanins of the chitons have relatively high half-saturation oxygen pressures. They may show a normal or reverse Bohr effect, or none at all. Regardless of the direction of the effect, however, these hemocyanins are relatively insensitive to small changes of pH. 5. The hemocyanins of marine snails studied have lower half-saturation pressures and all exhibited a reverse Bohr effect. 6. It is suggested that:(a) the properties of the hemocyanins are related to metabolic rate, accessibility and effectiveness of the gills, and the nature of the circulatory system;(b) an important function of many invertebrate blood pigments is to maintain a large oxygen diffusion gradient across the respiratory surface;(c) the reverse Bohr effect may aid in the internal distribution of oxygen to more rapidly metabolizing snail tissues when circulation is slowed or stopped. 7. A possible functional evolution of blood respiratory pigments is described.