In 15 °C air P. ochraceus was able to maintain oxygen consumption at levels similar to those in seawater, and thuscoelomic PO2 remained unchanged during emersion. In 25 °C air there was a slower increase in oxygen consumption, reachingmaximal levels after 4 h of aerial exposure. The rapid decline in coelomic PO2 despite the increase in oxygen consumption suggests that the gas transfer rate may have not been sufficient to meet the increased tissue demands. In addition the warming of the fluid would have reduced the solubility ofoxygen in the coelomic fluid. Interestingly there was a transient increase in PO2 when the starfish were exposed to 5 °C air, the decrease in body temperature could have slowed metabolism reducing tissue oxygen demand, while the lower temperature would lead to an increase the solubility of oxygen in the coelomic fluid. The fact that the animals were able to maintain and/or modulate oxygen consumption rates in air, suggests for this, as in other intertidal species, little anaerobic respiration takes place