Effects of hypoxia on oxygen uptake and surfacing behavior in the giant aquatic salamander Siren lacertina

Abstract

The greater siren (Siren lacertina) can acquire oxygen from both air and water (bimodal breathing). Currently, only physiological measurements have been made on bimodal breathing, with little work being done on the unique surfacing behaviors associated with this process. Flow-through respirometry was used to measure O2 uptake in increasingly hypoxic water. In addition, video recordings were made to capture and quantify the surfacing behavior of greater sirens in response to progressive hypoxia. Greater sirens showed an increase in aerial O2 uptake, a decrease in aquatic O2 uptake, and no change in total O2 uptake as the aquatic O2 tension decreased. Also, greater sirens shifted only the number of surfacing trips they made as the aquatic O2 tension decreased; all other surfacing behaviors remained unchanged. Greater sirens appear to maintain their metabolic rate despite the aquatic O2 tension solely by modifying the number of trips they take to the surface.