The oxygen consumption of Potamopyrgus jenkinsi (Smith)

Summary

• 1. The oxygen consumption ofPotamopyrgus jenkinsi from one brackish- and two fresh water localities (Fig. 1) during starvation has been investigated. For two localities there is an increase in oxygen consumption during the first 25 hours of starvation. Thereupon the oxygen consumption keeps at a constant level as with the third locality until about 90 hours of starvation, after which the oxygen consumption falls steadily for all the three localities. Measurement of the oxygen consumption has taken place up to 170 hours of starvation.

• 2. The oxygen consumption atP. jenkinsi from brackish- and fresh water has been examined (Fig. 2.). It was shown that the animals from one of the fresh water localities have a smaller oxygen consumption than animals from brackish water, which is connected with reduced growth of the freshwater animals. From another fresh water locality the oxygen consumption is, on the other hand, a little bigger than the oxygen consumption for the brackish water animals. This may be related to the fact that the animals appear to thrive better in this fresh water locality and so have been able to increase their metabolism in relation to the osmotic conditions.

• 3. Quantitative collections ofP. jenkinsi from one brackish water-and two fresh water localities have been made for 13 months, (Figs. 4 and 5). From one fresh water locality, Kolstrup marlpit N., big numbers of individuals appear, while large animals are never seen. From the other fresh water locality and from the brackish water locality such big numbers of individuals never appear, but very big animals are found.