National Repository of Grey Literature 23 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Evolution of prey-catching behaviour in poikilothermic vertebrates and its relationship with predator's visual perception
Košinárová, Lucie ; Frýdlová, Petra (advisor) ; Robovská, Pavla (referee)
Both the topics of prey-catching mechanism and visual perception are closely connected, affecting each other in many complex situations. The main subjects of this thesis were amphibians and reptiles and the many effects that impact their hunting abilities. We studied their hunting patterns in a few species of frogs and the leopard gecko (Eublepharis macularius) in an arena. We did not find any universal hunting pattern for neither of those groups, moreover even the quantity of individual sequences differed among them. However, hunting in nature is often engaged in habitats that are far from the flat calm arena. Often the animals have to adapt to different conditions, for example an unsteady surface underneath them. In such conditions they need to compensate for the passive movement with their heads and eyes to stabilize the image on their retina. The ability to compensate while hunting in frogs is affecting their behaviour and the success rate of their prey-catching. Another aspect that is influencing frog's hunting efficiency are their protrusible tongues that are commonly divided into three categories: mechanical, inertial and hydrostatic. The last goal of this thesis was looking for the evolution of this trait in frog's phylogenesis and their different effects on hunting movements.
Self-assessment and mutual-assessment ability in squamate reptiles
Čekal, Jakub ; Frýdlová, Petra (advisor) ; Kubička, Lukáš (referee)
Agonistic interactions throughout the animal kingdom can inflict various costs upon involved animals (decreased fitness, higher risk of predation etc.). To prevent such losses, many species have developed different morphological and behavioural adaptations to display their fighting ability. These adaptations allow animals better assessment of different costs and benefits associated with fighting. Assessment can be divided into two main categories based on the amount of information, that opponents take into account. Self-assessment assumes that rivals consider only their competitive ability and the potential benefits of winning a fight. During mutual-assessment competitors are also capable of considering possible differences in their apabilities and either escalate the fight or back down. My thesis is literary research of this topic in squamate reptiles. The assessment was characterized in several families of Squamata. Additionally, it evaluates the most important traits, that determine a potential winner and introduces different behavioural models of assessment. Used literature suggests that the most reliable predictor of fighting success within these families is the body size, and that mutual-assessment seems to be more prevalent. Keywords: assessment, RHP, aggression, agonistic interactions,...
Ecological Effects of Climate Change on Snakes
Veverková, Barbora ; Sedláček, Ondřej (advisor) ; Frýdlová, Petra (referee)
Climate change is currently one of the biggest threats that animal species must face. Increasing temperatures cause declines in wildlife populations all around the world. Ectothermic animals might be amongst the most threatened organisms by climate change due to their ecology that makes them dependent on ambient temperature. As ectotherms, snakes will most likely need to adapt to new climatic conditions, or they become extinct. To escape raising temperatures and decreasing precipitation, snakes might shift their ranges and move into more suitable areas. However, snakes have a low dispersal ability, which might lead to range reduction and in some populations even extinction. Climatic changes might affect health and behaviour of snake species as well. Increased temperatures can alter incubation period and embryonic development. Alterations in embryonic development and reduction of incubation period can cause different kinds of malformations, especially in oviparous snakes. These malformations can negatively impact fitness, depending on their severity. Some snake species might also benefit from climate change. Elevated temperatures allow snakes to be more active and, in some cases, even shorten hibernation duration. Snakes are also able to better escape predators in high temperatures than in low...
Evaluation of hybridization effect on fitness of eyelid geckos (Eublepharis, Gekkota) by performance tests
Kohoutová, Tereza ; Frýdlová, Petra (advisor) ; Sedláček, František (referee)
An interspecies hybridization is usually viewed from two sides - either as mistakes in a reproduction resulting in decrease of a hybrids fitness (e. g. loss or decrease of viability and fertility) or as a mechanism helping animals adaptively respond to environmental changes resulting in higher fitness. Fitness is usually represented as a set of correlates. One of the correlates is an organism performance which is represented by a set of maximal values from measured physical activities. This thesis focuses on the evaluation of the endurance and the bite force for gecko species E. macularius and E. angramayniu, their interspecies hybrids and intraspecies hybrids to determine their performance. The results show differences in the bite force among each of the tested groups. E. macularius has the lowest bite force, while the highest bite force was measured in E. angramayniu. The bite force of interspecies hybrids is intermediate in comparison to the parent species. Nevertheless, intraspecies hybrids of large form and white form of E. macularius exceeds their parents in measured bite force. The variability in bite force suggests a positive effect of hybridization on fitness. The bite force differences between the large form and the white form of E. macularius support the hypothesis that there exist more...
Ontogeny and evolution of body size and sexual size dimorphism in reptiles
Frýdlová, Petra
Monitor lizards (Varanidae) are morphologically very uniform in body shape, but much diversified in body size along both phylogenetic and ontogenetic axes. A striking sexual size dimorphism exists in monitor lizards; they are capable of fast growth, metabolism and sexual maturation. I collected the data concerning body size of particular species and verified the validity of Rench's rule, which said that there is bigger difference in body size of a conspecific male and females growing with larger body size of the species. Males are markedly bigger than females. In the next step, I focused on the model species of monitor lizards, Varanus indicus. I monitored its ontogeny very carefully. I found that this monitor lizard has pronounced sexual size dimorphism, but there are only small differences in body shape. It is capable of rapid growth and sexual maturation. The sexual dimorphism in body shape is only poor, but still measurable right in those places where the selection pressures were expected. Blood sampling monitored biochemical and haematological parameters. The concentrations of the biochemical parameters revealed the economy of resources of particular sexes partially, the costs of body growth and reproduction. Although both sexes produce the same amount of biomass (the body growth of males vs....
Developmental plasticity in reptiles
Peš, Tomáš ; Kratochvíl, Lukáš (advisor) ; Frýdlová, Petra (referee)
The environment during incubation can have significant influence upon phenotype of reptile hatchlings. Temperature is one of the main environmental factors affecting developing embryos. The response to variability in the environment can be diverse: short, long-lasting and potentially also sex-specific. A large number of studies focused on this phenomenon but only a small portion of them studied the persistence of the phenotypic effects. I summarized studies on the influence of environmental factors on the phenotype of reptiles in species with both temperature or genotypic sex determination. These studies were evaluated in terms of duration of these effects and if these are sex specific. I also assessed how much they correspond with the predictions of the adaptive model suggested by Charnov & Bull which explains the origin and maintenance of temperature sex determination. Key words: phenotypic plasticity, environment, development, behaviour, morphology, sex determination, phenotype
Energetic costs of tail autotomy and regeneration in reptiles
Píchová, Veronika ; Starostová, Zuzana (advisor) ; Frýdlová, Petra (referee)
Most reptile species have the ability to voluntarily cast off their tail, known as autotomy, followed by tail regeneration, which is used as an antipredatory mechanism. In spite of this being a successful ecological adaptation, the individual with its tail cast off is often influenced negatively, which includes increased probability of predation, lower locomotion capabilities, lower immunity or a change in its social standing. Last but not least, casting off the tail and the following regeneration may distinctively influence the energy of the individual, either directly through the loss of fat reserve, usually located in the tail itself, or because the regeneration of lost tissue demands a lot of energy and often requires relocation of energy at the expense of other processes. Autotomy and regeneration of the tail may thus influence important traits of physiological processes such as body growth or body mass, reproductive capabilities or metabolism intensity. The influence of autotomy on these aspects of an individual's life has been a studies topic in the last few years, but conclusions vary. The goal of this thesis is a brief summary of information about the mechanism of caudal autotomy and regeneration and also summarize contemporary knowledge about energy costs connected to autotomy and...
Assisted reproductive technology in reptiles
Kánská, Barbora ; Kratochvíl, Lukáš (advisor) ; Frýdlová, Petra (referee)
The thesis deals with assisted reproduction techniques in reptiles. The class of reptiles (Reptilia), as is classically described, is paraphyletic taxa. That is the reason why birds (Aves) are included for completeness of this thesis. For the sake of clarity, the term "reptiles" is used in the thesis within the meaning of traditional reptile orders (squamates, tuataras, chelonians and crocodilians), which together with birds form the monophyletic class Sauropsida. The development of assisted reproduction techniques has been mainly focused on mammals so far. However, given the numbers of endangered species of reptiles and birds, it is clear that more attention should be paid to them, as assisted reproduction techniques can represent one of the ways to prevent their extinction. This thesis deals with those methods. Semen collection and its subsequent storage represent the first step to successful artificial insemination or in vitro fertilization. Cryopreservation and following transplantation of ovarian and testicular tissues (already successful in birds) is a promising method for conservation programs in endangered animal species. Furthermore, captive animal breeding is briefly mentioned, which is not an assisted reproduction technique in the true sense of the word, but offers an example of saving...
Hunting mechanism and visual perception of prey in amphibians
Košinárová, Lucie ; Frýdlová, Petra (advisor) ; Černý, Rudolf (referee)
Visual perception holds the dominant position among other senses in amphibians. It provides vital information about any potential prey or predators in the surrounding area. Any information, gained through optical sensors, is then directly evaluated in brain, activating different behavioral reactions: prey catching or predator avoidance behaviour. Decision is based on individual parameters of stimuli. In case of identifying a prey stimulus an innate behavior pattern is activated. There are many prey catching strategies in amphibians. Their selecting may vary due to many aspects including food preferences, mechanical constraints or a phylogenetic position of the species. Habitat may also have an influence over hunting strategy or even morphological characters of species, mostly regarding their oral system. Tongue plays an important role in almost every prey catching movement in terrestrial and also in some aquatic amphibians. There are different types of tongue elongation in amphibians that are divided into several categories, which can affect the hunting strategy for each species. Apart from creating a summary about visual perception and hunting mechanisms, this thesis includes a mapping of different types of tongue elongation on a phylogenetic tree of amphibians. The main goal of this task is to find a...
Perception of the human disturbance by ungulates in the wild and in the captivity
Šťastná, Tereza ; Komárková, Martina (advisor) ; Frýdlová, Petra (referee)
The relationship between ungulates and humans has been evolving ever since the first predator's interaction with the prey, leading to the current domestication. The behavior of ungulates differs based on the human disturbance. The goal of this thesis was to compare the reactivity to humans of selected species in nature vs. in captivity and determine its correlation, inter or intraspecific. The thesis indicates reactivity to humans of specific species of ungulates (donkeys, horses, reindeers and goats). Following reactions were chosen for comparison: vigilance, alert distance, flight and avoidance distance. There are several acting factors like previous experience with humans, habituation, group size or season. With group size, the vigilance decreased, which was proven with donkeys, reindeers and goats. The behavior differed based on the season by resources availability, offspring's presence in herd (higher vigilance) or rut (lower vigilance). In captivity, there were less human contact avoidance, while the experimenter was known. Based on researches, ungulates tend to avoid humans more in nature, than in captivity. Sources claim, that among chosen ungulates, the most vigilant in both nature and captivity are reindeers. Further researches could later consider the human perception according to the...

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