National Repository of Grey Literature 71 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
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
Phylogeny, diversification dynamics and biogeography of Hemidactylus geckos
Janák, Vojtěch ; Šmíd, Jiří (advisor) ; Kratochvíl, Lukáš (referee)
Hemidactylus is the second-most speciose among all gekkotan genera and also accounts very well for most typical characteristics of the group, such as almost worldwide distribution and significant species diversity. Many new species have been described in recent years, doubling the over all species count. Although the amout of knowledge regarding this genus has grown significantly, there is still some confusion in the matter of clade relationships on high as well as low levels of phylogeny. This thesis aims to summarize current knowledge of phylogeny and biogeography of this genus and its subclades.
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...
Cellular scaling rules for brains of gallinaceous birds
Zhang, Yicheng ; Němec, Pavel (advisor) ; Kratochvíl, Lukáš (referee)
Galliform birds (Galliformes) make up together with anseriform birds (Anseriformes) the clade Galloanserae, the sister group of Neoaves and the most basal clade of Neognathae. However, to date no quantitative data on cellular composition of their brains have been available. Here, I used the isotropic fractionator to determine numbers of neurons and non-neuronal cells in specific brain regions of 15 species of galliform birds. I find that cellular scaling rules for galliforms differ starkly from those for songbirds and parrots. When compared to these crown avian lineages, galliform birds feature lower degree of encephalization, a proportionally smaller telencephalon, small telencephalic and dominant cerebellar neuronal fractions, generally lower neuronal densities and larger glia/neuron ratios. Consequently, their brains and especially their forebrains harbor much smaller absolute numbers of neurons than those of equivalently sized songbird and parrots, the fact that undoubtedly constrains cognitive abilities of galliforms. However, this not to say that galliform birds are "bird brains" with low numbers of neurons and a limited ability to learn. Because they have high neuronal densities, their relatively small brains contain about equal numbers of neurons as brains of equivalently sized rodents and...
Evolution of sex determination and sex chromosomes in snakes
Charvát, Tomáš ; Kratochvíl, Lukáš (advisor) ; Šmíd, Jiří (referee)
Snakes form with almost 3700 described species more than one third of all squamate reptiles. The vast majority of snake species belong to the group Caenophidia, which is the best explored group of snakes for sex chromosomes. In contrast, sex chromosomes of the two other groups of snakes - Scolecophidia and Henophidia have so far been paid little attention. All snakes studied so far possess genotypic sex determination. Representatives of all Caenophidian families were observed with a female heterogamety sex determination system (ZZ/ZW) and it was widely accepted that this system was common to all snakes. This claim was recently refuted when a male heterogamety (XX/XY) was confirmed in a python (Python bivittatus) and a boa (Boa imperator), two representatives of Henophidia. In Henophidia, besides the XX/XY system, the ZZ/ZW system was reported in the only known representative of this group with heteromorphic sex chromosomes - A. sp. cf. dumerili. Sex chromosomes or sex determination systems are unknown in Scolecophidia. Caenophidian heteromorphic sex chromosomes have enabled the study of the phenomena associated with the gradual differentiation of sex chromosomes. These include W chromosome degeneration, the accumulation of repetitive elements, the fast Z phenomena, gene dosage compensation, and...
Evolution of sex chromosomes and karyotypes in iguanas (Squamata: Pleurodonta)
Altmanová, Marie ; Kratochvíl, Lukáš (advisor) ; Kejnovský, Eduard (referee) ; Zrzavá, Magda (referee)
Evolution of sex chromosomes and karyotypes in iguanas (Squamata: Pleurodonta) PhD Thesis Marie Altmanová Abstract This PhD thesis is composed of five published articles and one manuscript, and is focused on the evolution of the sex chromosomes and karyotype of the iguanas (Pleurodonta). Based on our primary research of available data, only male heterogamety (XX/XY) with ancestral karyotype 2n = 36 chromosomes was recorded in iguanas. However, in many species sex chromosomes have not been uncovered by classical cytogenetics, probably due to their homomorphy. The partially-known X chromosome content of Anolis carolinensis allowed us to compare the relative gene doses of X-specific genes between male and female of representatives of all iguana families, and to reveal homologous and well-differentiated sex chromosomes across all iguanas, with the exception of basilisks. Thus, due to the comparable age with sex chromosomes of mammals and birds, the results put into question the importance of endothermy for the formation of stable sex chromosomes. The striking feature of the iguanas is the relatively frequent occurrence of multiple sex chromosomes in their karyotypes. Using the ancestral state analysis of the type of sex chromosomes, it has been found that these multiple sex chromosomes developed at least twelve...

National Repository of Grey Literature : 71 records found   1 - 10nextend  jump to record:
See also: similar author names
5 KRATOCHVÍL, Lukáš
1 Kratochvíl, Leoš
2 Kratochvíl, Lubomír
1 Kratochvíl, Lumír
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