REACTIONS OF DACE TO LINEAR ACCELERATIONS

It is demonstrated that the rheophilic fish dace (Leuciscus leuciscus) is able to detect the direction of its movements in a water flow by p erceiving and analysing positive and negative accelerations from 15 up to 50 cm s-2, by the use of labyrinth organs. Tests were conducted on fish with 'switched off' mechanoreceptors and labyrinth organs under conditions which eliminated the use of visual orientation. It was also demonstrated that the values of linear accelerations which stimulated dace compensatory movements against water currents were comparable wi th the values of accelerations which could arise in river flows as a r esult of pulsation in current velocity. The results support the hypoth esis that rheophilic fish are able to use inertial stimuli for their s patial orientation.