THE INFLUENCE OF ABIOTIC FACTORS ON PHOTOTROPISM OF GASTROPODS <i>LYMNAEA LAGOTIS </i>SCHRANK AND <i>SEGMENTINA MONTGAZONIANA </i>BORGUIGNAT
Four types of experiments have been carried out to reveal the influence of abiotic factors on phototropism of two species of gastropods: (1) under the normal conditions, (2) under the preliminary light adaptation, (3) under the increasing of light intensity and (4) under the decrease of water temperature. Lymnaea lagotis preferred the more illuminated areas in all the mentioned types of experiments. They also moved to the light source under the water temperature decrease. Segmentina montgazoniana actively moved to and from the light source, with negative phototaxis prevailing. The most pronounced negative phototaxis appeared under the water temperature decreasing.