Cutaneous and gill O2 uptake in the European eel (Anguilla anguilla L.) in relation to ambient PO2, 10-400 Torr.

The partition of O2 uptake between gills and skin was examined in the freshwater eel (Anguilla anguilla L.) at ambient PO2 ranging from hyperoxia (PO2 = 400 Torr) to severe hypoxia (PO2 = 10 Torr), using a technique of open-flow respirometry. All the expired water was collected, and the ventilatory flow and the mixed expired water PO2 were directly measured. The ventilatory water flow decreased moderately in hyperoxia, increased markedly between normoxia and 40 Torr, and below 40 Torr, hyperventilation was gradually reduced. Between PO2 400 and 70 Torr, the total O2 uptake was constant and the skin O2 uptake was lower than gill O2 uptake (32% of total uptake in normoxia). Between 70 and 10 Torr, the skin contribution to the total O2 uptake progressively increased, and was higher than gill O2 uptake in severe hypoxia. A possible facilitation of cutaneous O2 uptake in hypoxia is discussed from estimates of the O2 diffusing capacity of the skin.