Aerotaxis by the freshwater oligochaete Tubifex sp.

1. The influence of oxygen on the direction of movement (aerotaxis) by the freshwater oligochaete, Tubifex sp., was investigated by monitoring the behaviour of adult animals in different oxygen gradients. 2. The results show that Tubifex expresses negative aerotaxis, i.e. moves away from oxygen, with preference for anoxia. 3. The time course of Tubifex movements in oxygen gradients shows that the mechanism of aerotaxis is both sensitive and fast. This suggests that Tubifex possesses some kind of oxygen sensor by means of which it is able to recognize even small oxygen gradients.