New Results Concerning Gravitaxis of Paramecium.

Kurzfassung

Gravitaxis of Paramecium was investigated by observing and analyzing the behavior of the cells in a vertical cuvette. The degree of negative gravitaxis strongly depends on the oxygen concentration within the medium: At low O2 the negative gravitaxis is very precise, while with increasing oxygen concentrations a more random distribution occurs. Under optimal oxygen conditions Paramecium swims slower than in a low-oxic environment. If the cells are in low-oxic conditions for a longer period, the initial relation between degree of orientation and swimming velocity does no longer exist: Though the swimming velocity of the cells gradually decreases, the precision of their taxis even persists after one day. Another essential observation is that the cells swim faster upwards than downwards.These facts give strong evidence that gravitaxis of Paramecium is an actively regulated reaction of the cell.