The Oxygen Consumption of Ephemerid Nymphs From Flowing and From Still Waters in Relation to the Concentra-Tion of Oxygen in the Water

The data are best summarized by reference to Fig. 1. An extreme contrast is presented by Cloëon dipterum and Baëtis sp. in the relation between oxygen consumption and oxygen concentration in the water. When the oxygen in the water diminishes, the oxygen consumption of Cloëon dipterum does not decrease until the oxygen has fallen below one-fifth air saturation, whereas the oxygen consumption of Baëtis sp. falls immediately the oxygen in the water decreases. Above air saturation, the oxygen consumption of Baëtis sp. rises until it reaches 1½ times its value in nature. The oxygen consumption of Baëtis scambus is almost independent of oxygen in the water, both above and below air saturation. The oxygen consumption of Ephemera vulgata falls soon after the oxygen in the water begins to diminish. Above air saturation it rises slightly. Leptophlebia vespertina somewhat resembles Cloëon dipterum: its oxygen consumption falls slowly until one-third air saturation is reached, below which there is a sudden drop. There is a relation between oxygen consumption and size of animal. The oxygen consumption of the larger species Leptophlebia marginata is lower than that of the smaller species L. vespertina, and the oxygen consumption of the larger Baëtis scambus is lower than that of the smaller Baëtis sp.