Respiratory properties of the blood of a lungless and gill-less salamander, Desmognathus fuscus

Abstract

Plethodontid salamanders have neither lungs nor gills and depend upon cutaneous gas exchange to satisfy metabolic requirements. We have examined some respiratory properties of the blood of Desmognathus fuscus (Plethodontidae, Urodela) to determine whether special properties exist in this species which facilitate the transport of gases between the skin and tissues. Hemoglobin concentration, hematocrit, and O 2 capacity were 7.5 g%, 28% and 9.8 vol% respectively. The O 2 hemoglobin dissociation curve is slightly sigmoid in shape (n = 2.64) with a P 50 of 27 torr at in vivo P co 2 and 13 °C. The buffer value for whole blood was 13.2 mmol · 1 −1 · pH −1. The pH of systemic arterial blood was low (7.51) even though the P CO 2 was 6.2 torr. Bicarbonate concentration was 9.15 mmol/1. Even though there was complete mixing of oxygenated and non-oxygenated blood, the P O 2 in systemic arterial blood was 40 torr, corresponding to an O 2 saturation of 70%. Cutaneous respiration may be viewed as freeing plethodontid salamanders from ventilation limitations, being suited for gas exchange in both water and air.