THE RESPIRATORY FUNCTION OF THE BLOOD OF MARINE FISHES

Abstract

Determinations were made of the O capacities, O dissociation curves, and CO2 absorption curves of the blood of marine fishes. The effect of CO2 on O capacity was also investigated, as well as buffering capacities. Opsanus tau, Prionotus carolinus, and Scomber scombrus furnished most of the results. The sluggish 0. tau has a blood of very low 0 capacity, whereas the active S. scombrus has a blood of relatively high O capacity. All bloods are very sensitive to CO2, the O dissociation curves being remarkably flattened in its presence. The O capacity of the bloods also drops markedly in the presence of CO2. These observations have prompted the suggestion that more than a simple Bohr effect is produced, that, perhaps, certain of the prosthetic groups in hemoglobin are inactivated. A differential buffering ability, as well as CO2 combining power, is shown by these bloods. This appears to be correlated with hemoglobin concentration. On the whole, marine fish blood has low CO2 combining power and poor buffering capacity. The general results indicate an adjustment on the part of marine fish blood to a seawater environment. At the same time comparisons made between marine fish blood and the blood of other vertebrates point to the conclusion that the differences present can be accounted for on the basis of the peculiar morphological, physiological, and ecological differences that concern each type of vertebrate.