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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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How predation risk affects the growth and development of dragonfly larvae?
PEROUTKA, Miroslav
Predation and prey responses to predators in aquatic environment are reviewed with emphasis on non-lethal effect of predators on prey life history, antipredator behavior and related mechanisms. The review focuses on dragonfly larvae and other groups of prey with complex life histories, mainly anurans. The review is complemented by laboratory experiments examining the effects of varied food availability and predation risk on a selected species of dragonfly, Sympetrum vulgatum.
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Aggregations as an antipredator strategy in common toad tadpoles (\kur{Bufo bufo}).
BODNÁR, Tomáš
Tadpoles of many anuran species use a huge number of behavioral modifications to avoid predators. Reduced activity in presence of predators is favorite strategy for common toad tadpoles (Bufo bufo). Responses against predator cues by tadpoles of Bufo bufo in the presence of another cue of larger tadpole aggregation were tested in this study. We observed that these tadpoles responded differently to predator chemical cues than tadpoles in a small group.
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Circadian activity of tadpoles of Phyllobates vittatus.
DOSTÁLOVÁ, Michaela
Tadpoles are known to behaviorally respond to visual, auditory or chemical cues. I examined the influence of group size and light conditions on the activity of Phyllobates vittatus. I performed laboratory experiments to measure locomotor activity. Activity levels of tadpoles were higher in the groups. Light conditions did not influence activity level of tadpoles. My results suggest that the group size is one of the main factors influencing tadpole locomotor activity of Phyllobates vittatus.
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