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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...
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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....
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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
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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...
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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...
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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...
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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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The effect of steroid hormones on sexually dimorphic bone growth in geckos
Tureček, Adam ; Kubička, Lukáš (advisor) ; Frýdlová, Petra (referee)
The sexual size dimorphism (SSD) is widespread among animals but proximate mechanisms of its ontogeny are still poorly understood even in important groups of vertebrates such as reptiles. Previous experiments in geckos showed that growth of both sexes slows substantially at their older age. Their SSD develops considerably a long time after sexual maturity, it is associated with earlier growth deceleration in the smaller sex and it is controlled by ovarian rather than testicular steroids. The aim of the thesis was to explore the previous knowledge by studying the ontogenesis of the sexually-dimorphic bone growth of the gecko Paroedura picta, the male- larger species with the most explored proximate mechanisms of SSD among geckos. I was most interested in the ontogeny of the growth plates activity and the epiphyseal ossification of the femur in both sexes and their relationship to age, body length, gonadal activity and levels of sex-specific steroids (estradiol and testosterone). The results show that P. picta has determinate growth and that epiphyseal ossification does not contribute to the SSD. The femoral growth plates close at the same age in both sexes; however, their closure occurs at smaller body length in females than in males. In the context of this and the previous studies, estradiol or other...
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The role of cell size in body size change in animals
Hájková, Věra ; Starostová, Zuzana (advisor) ; Frýdlová, Petra (referee)
Animals are very variable in body size. Differences in body size are visible not only at the interspecific level but also within species, whether they are differences in size during ontogeny or among individuals of the same species exposed to different environmental conditions. The size of the organism depends on the size and number of the basic units from which it is built, i.e. the cells. From this perspective body size can be changed only in three ways: by changing the cell size, by changing the number of cells, or by combining these two mechanisms. It is assumed that during development an individual can be affected by many environmental factors that can alter cell size and/or cell number. The most discussed one is the environmental temperature. Quite often, organisms that live or develop at low temperatures reach larger body sizes, and it was repeatedly found that the body size increase is associated with increase in cell size. In addition to temperature, the size and number of cells, and consequently the body size, can be affected for example by oxygen concentration or by quality of nutrition. Environmental factors can interact with each other and often it cannot be clearly stated that changes in size or number of cells are caused only by one particular factor. Although there is a clear need...
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