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Is the growth of brown frog's tadpoles influenced in different stages of its development by the presence of red-eared slide?
VODRÁŽKOVÁ, Magda
In the last few decades, the frequency and importance of invasive species has been increasing mainly due to the disproportionate growth of world trade in animals and plants. Predator-prey interactions drive the evolution of many behavioral and morphological traits in aquatic animals. In aquatic environments, chemical cues reliably enable prey to assess and avoid predation risk. The presence of a predator affects prey populations either by direct predation by reducing its abundance and changing its behavior, or by modifying various parts of its life history. The effect induced by the risk of predation can have a stronger impact on populations than the direct effect of mortality. Non-native red-eared sliders (Trachemys scripta elegans) have the potential to disrupt aquatic ecosystems in Central Europe because of their superior competitive abilities and omnivorous diets. I investigated whether continuous predator-borne cues are tied to changes in the hatching time, developmental stage, and body size at hatching of common frog tadpoles (Rana temporaria). Whether the developmental rates, growth rates and sizes at metamorphosis would alter in the presence of a predator and examined the dynamics of the ontogeny of tadpoles under different time patterns of an alien predator presence. The presence of a predator affected all factors examined. I found that in the absence of the slider, the embryos hatched in 12 days, while hatching was accelerated by two days in slider treatment. At the same time, the embryos hatched smaller and at a lower stage of development with the slider than without it. The presence of turtles shortened the time at metamorphosis of tadpoles from 110?11.7 days to 93?13.0 days (mean ? S.D.). The froglets were significantly smaller (12.8?0.99mm) in the presence of the predator than in the control treatment (15.2?1.27mm). The growth rate trajectories were similar between the predator treatment and the control. Thus, predator-induced tadpole defences were evident in higher developmental rates and smaller sizes at metamorphosis without significant changes in growth. I also found out that the tadpoles had a longer larval period and were smaller in size at metamorphosis and lower in body mass when the predator was present in early development than when the tadpoles developed without a predator. The early presence of a predator conspicuously reduced the growth increments of the tadpoles at early development. After the removal of the predator, growth accelerated above the level measured under the conditions of both the late predator and no predator. However, these growth rates did not exceed the growth rates of equally sized tadpoles in the other treatments and therefore were not sufficient to compensate for the growth slowdown in the first part of development. The presence of a predator in late tadpole development influenced neither the time to metamorphosis nor size/body mass at metamorphosis. Results show rather rarely documented types of amphibian prey responses to caged predators. This study extends the range of predators studied, including the effect on different phases of development of potential amphibian prey.
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Is the growth of brown frog`s tadpoles influenced by the presence of red-eared slides?
VODRÁŽKOVÁ, Magda
An increasing amount of attention is devoted to studying the impact of non-native animal species on native species. Among other causes of ecosystem degradation, such as climate change, polution and habitat conversion, biological invasion is considered as one of the main causes of the decrease in biological diversity all over the world. In order to detect possible predation event, tadpoles use not only visual and mechanical stimuli, but also chemical one. The tadpoles respond to the certain chemicals to be a part of predator's secretions. In aquatic systems, chemical cues are a major source of information through which animals are able to assess the current state of their environment to gain information about local predation risk. Prey use chemicals released by predators to mediate a range of behavioural, morphological and life-history antipredator defences. Tadpoles swim significatnly less and also on a less direct trajectory in the presence of chemical cues released by a turtle Trachemys scripta. This article is focused on the influence of mentioned constraints on the dynamics and the time dynamics of the larval growth of Rana temporaria. The influence was judged by the impact on the tadpole's development. We anticipated a behavioral response to the predator, which would lead to various growth reactions during larval growth, the resulting body size after metamorphosis, but also in the development time of larval stage. The results indicate that tadpoles of Rana temporaria changed behaviour in the presence of Trachemys scripta. Tadpoles in the permanent presence of the turtle grew faster, metamorphosed earlier and the resulting size after metamorphosis was smaller than of the tadpoles who developed without presence of the predator. Mentioned reactions may affect the survival and fitness of a metamorphosed individual.
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Toe-clipping in amphibians and its effect on survival
VODRÁŽKOVÁ, Magda
This bachelor´s thesis deals with labelling of amphibians. The most it is focused on the method called toe clipping, applications for individual species of amphibians and their survivability. As well the thesis contains a summary of several technics used at amhibians. It compares advantages and disadvantages and the comparison of this methods as well.
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