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National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Has UV radiation an impact on tadpoles' movement activity?
 KLAPKA, Vladimír
The increasing level of the UV-B irradiation due to depleting of the ozone layer is considered to be one of the causes of global amphibian declines. The UV-B radiation causes damage to the DNA in the nuclei of the skin cells and their eventual death. In many amphibian species there was found a negative influence of the UV-B radiation on the hatching success of tadpoles and their subsequent viability. It has been assumed that tadpoles are able to actively avoid places with the higher exposure of the UV-B radiation thanks to their locomotion. In this experiment tadpoles could have chosen between a zone with the UV radiation (UV-B and UV-A) and without the UV radiation. The tadpoles have not been exposed to the UV radiation before the measurement started. The location of the tadpoles during the measurement was recorded by CCD camera. A computer program EthoVision then evaluated the time that these tadpoles spent in each of the zones and the total path length these tadpoles has swum in the zones. The measurements were performed for two groups of tadpoles differing in age to determine whether the level of development may affect the tadpoles' preference to the UV radiation. The tadpoles in both groups spent more time in the zone without the UV radiation. The tadpoles in the more advanced development phase have spent 7 times more time in average in the zone without the UV radiation than in the zone with it. The tadpoles from the second group have spent in average 2.5 times more time in the zone without the UV radiation than in the zone with the UV radiation. The total swimming path length of advanced tadpoles was almost 2.5 times longer in the zone without the UV radiation than in the zone with the UV radiation. Conversely, the total path length of younger tadpoles did not significantly differ between the zones. The total time spent in the zones with / without the UV radiation did not differ between the groups of tadpoles. Also the total path length did not differ between the groups in the zone with the UV-B radiation. However, the total path length of tadpoles had differed between groups in the zone without the UV radiation.
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The influence of the presence of invasive map turtle on the activity of brown frog tadpoles.
 KLAPKA, Vladimír
The thesis focuses on the factors that influence locomotor activity of tadpoles. An important factor is the risk of predation. The presence of a predator or its metabolites induced in many species of tadpoles reduced locomotor activity. Another factor that affects the locomotor activity of the tadpoles is the presence in the group of conspecific individuals. A laboratory experiment was created to evaluate the influence of these two factors on the locomotor activity of Rana temporaria tadpoles in the presence of metabolites of invasive turtle Trachemys scripta elegans. In the experiment, the rate of tadpole's locomotor activity was expressed by the length of tadpole's trajectory which was measured by camera and evaluated by EthoVision software. The measurement results show that tadpoles in the presence of metabolites of turtle showed antipredator behavior, reduce their locomotor activity. The presence of the tadpole in group with 5 other conspecific individuals did not affect the locomotor activity. The group could only communicate with chemical signals. Conversely interaction was found between the effect of the presence of metabolites of predator and influence group. Tadpoles in the group in the presence of a predator showed greater locomotor activity than single tadpoles in the presence of these metabolites.
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