Intensity of the positive phototropism in some hydrobionts under the natural conditions

The phototropism of the fresh-water hydrobionts has been studied under the natural conditions. The new approach to the study of the phototropism in water invertebrates with an aid of light-traps is developed. The direction and intensity of the reaction of the phototropism are quite variable. The phototropism of hydrobionts is adaptive and linked with the peculiarities of their biology. The closest relation with the habitat and the way of breathing is revealed. This shows, that the light plays a signal function as an indicator of both water surface and the open water.