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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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Social interactions and morphometric analysis of populations of Blue-Tongued Skink (Tiliqua gigas)
Jachnická, Kristýna ; Frynta, Daniel (advisor) ; Rehák, Ivan (referee)
A Blue-tongued skink ( Tiliqua gigas) is a rare exotic species which is very popular between breeders. Nevertheless, the social structure of this charismatic skink remains almost unknown. Because of its high aggressive- ness and difficulties connected with study in its natural habitat, experiments based on the odor discrimination looks like a good alternative for its bet- ter understanding. Our results revealed that the reaction on the odor is generally poor and is very individual. We observed the highest response of interest on odors produced throught dorsal parts of skin. The reaction on conspecific's odor did not lead to escape behavior. Behavioral analysis was complemented by morphological analysis of heads in T. gigas and T.scincoides. These species are divided into separate subspecies, which are formed by geographically distinct populations. We wondered whether it is possible to separate these populations by geometric morphometrics and whether this separation is consistent with phylogenetic studies. We found out that if the populations are united in bigger groups based on their congeniality they seem to be distinct according to the head shape. Our results also revealed the monomorphy in head shape. Unfortu- nately, it is very difficult to distinguish between sexes due to the absence of sexual dimorphism....
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Can birds manipulate sex ratio of their offspring?
Tomiška, Lubomír ; Kratochvíl, Lukáš (advisor) ; Fuchs, Roman (referee)
The aim of this study is a summary of existing knowledge about skewed sex ratio in birds. This controversial topic represents one of the most important questions of evolutionary ecology. We still miss consistence in finding ultimate causes just as proximate mechanisms although there was an expansion of experimental studies already in the last decade of the 20th century which was caused by an invention of the new technology in sex determination. On the other hand, there are many convincing proofs of skewed primary, secondary, tertiary and even quartenary sex ratio so the facultative manipulation or obligatory sex ratio bias is presumable. My Bachelor's thesis compares studies focused on the similar ultimate causes and tries to point out their deficiencies together with contributions to research of this topic. Observation of sex ratio includes many specifics which are mentioned in theoretical introduction. The second part offers potencial proximate mechanisms which could be responsible for sex ratio manipulation. Within the analysis of studies I found sex ratio manipulation of the first egg in clutch as common trend which could fit to selective ovum resorption as a proximate mechanism.
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Evolution of sex chromosomes and karyotypes in geckos (Squamata: Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Choleva, Lukáš (referee)
Gekkota is species-rich and diverse group of squamate reptiles (Reptilia: Squamata) with almost global distribution. There were many hypothesis defined about the phylogeny of this group, traditionally based on morphological data. The essential reversal in phylogenetic relationships occurred with the entry of molecular analysis, whose differ in their conclusions from traditional approach fundamentally, even in positions of mayor lineages. This fact has an essential importance for the karyotype evolution study of this group. The ancestral state is considered as 2n=38 karyotype with all chromosomes acrocentric. In some species is this karyotype kept, in another there is apparent an influence of chromosome changes, mostly Robertsonian fusions and pericentric inversions. Diploid chromosome number is from 16 to 46, but the most common is 2n=38 karyotype of mostly acrocentric chromosomes, gradually decreasing in size. The interesting character of this group is extraordinary variability in sex determining mechanisms. We can find there species with temperature sex determination and also species with genotypic sex determination (both types XX/XY and ZZ/ZW). Sex chromosomes data are documented in only 17 species. Sex chromosomes differ rapidly in their morphology and their homology between sister taxa was not proved...
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Gene mutations affecting the development of human testes
Macháčová, Simona ; Šebková, Nataša (advisor) ; Ševčíková Jonáková, Jana (referee)
Development of mammalian sex organs is remarkable process. Both ovaries and testes rise from the same precursor but then differentiate into morphologically and functionally different structure. The determining factors that decide the fate of undifferentiated structures are not just the genes themselves but also the timing of transcription regulatory genes and specific amount of their products. Development of male and female gonads manages a large set of regulatory genes that interact with each other. Together it forms the gene regulatory network. Crucial role in male sex differentiation plays an SRY gene which regulates the time and quantity of the other factors expression. Even slight errors (mutations) in genes sequences of regulatory genes could change their expression. This leads to disruption of the development of sex organs or even death of the whole organism. Naturally occurring mutations and their phenotype in humans are suitable for studies of gene sex regulatory factors. Thanks to these studies we are able to detect the cause of many birth defects what is a first step toward their eventual treatment.
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Secular trend, inter-population variability and sex estimation with help of variables of human femur.
Švenkrtová, Iva ; Brůžek, Jaroslav (advisor) ; Velemínský, Petr (referee)
Determination sex is one of the most important tasks in the identification of skeletal remains. Previous studies have shown that population differences in size and shape of femora can affect correct sex allocation. This thesis tested the discriminat functions generated from different populations and confirmed population specificity of the femur discriminant functions. Two samples of the identified adult femora for this project was used. First sample originates from the Czech population living in the 1st 20th century (78 males and 81 females) and second sample originates from the Czech population living in the 2nd 20th century (67 males and 35 females). Both samples also help us estimate the influence of secular trend of the femur'variables to the correct sex classification by discriminat functions calculated in the Czech population. The results showed the existence of the secular trend in femora size dimensions. Only the dimensions of the femoral head (vertical head diameter-F18, transverse head diameter-F19 and maximum diameter of the femoral head-MPH) and sagittal subtrochanteric diameter (F10) not chandged significantly during the 20th century. The secular trend has negatively influenced the correct sex classification, always for one subpopulation. Only the dimensions in which the secular trend...
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Sexual size dimorphism in medieval period in Bohemia.
Kaupová, Sylva ; Brůžek, Jaroslav (advisor) ; Dobisíková, Miluše (referee)
Differences in height among human populations or changes in height over time may be associated with different degrees of sexual dimorphism in this feature. This thesis compared the height and sexual size dimorphism (SSD) between two groups of the population of Medieval Bohemia - rural residents and inhabitants of Prague. A sample of 179 adult skeletons from five Prague sites and 175 individuals from four rural sites, dating from the 11th to 14th century, was used. Sex was determined following the principle of primary and secondary sex diagnosis, which enabled the derivation of population-specific discriminant functions using the dimensions of the humerus, femur, tibia and talus. A subsequent analysis of body height did not show statistically significant differences either in height or in SSD between the Prague and the rural part of the population of Medieval Bohemia, despite the major changes which Czech Medieval society went through in the 13th century. Comparing our results with previously published data on the height of the Czech population during the early modern period indicates a statistically significant reduction in the magnitude of sexual size dimorphism in the population of the17th century, particularly associated with a decrease in the height of men. A significantly higher stature of...
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Optimization of DNA isolation method for molecular sexing of birds
DILLINGEROVÁ, Hana
The aim of the bachelor thesis is to work up literary research on various methods suitable for bird sex determination. Furthermore, the experimental section of this work to determine the best suitable bird sex DNA isolation method and verifies the applicability of the isolated DNA for bird sex determination by PCR. The samples for DNA isolation were extracted from collected feathers and buccal swabs of animals kept on the university farm located in České Budějovice and of private animal keepers within the period of year 2015 and 2016.
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Influence of season of nesting on the sex ratio of chicks of parrots genus \kur{Neophema}
PAPAČ, Martin
This bachelor thesis represents complete summary of most of avian sex ratio studies. A very important moment was discovering of PCR analysis in 90's. This method enables to determine sex at molecular level. Older works which lacked PCR could not determine sex reliably and therefore their results can be misleading. PCR can determine sex ratio at primary, secondary and tertiary level. Sex ratio manipulation in birds is probable evolutionary mechanism and there are several hypothesis regarding to that. Many experimental studies have shown possible ultimate and proximate causes which are responsible for sex ratio manipulation. However, low data sample was one of the causes why they have been considered to be doubtful. I have summarized several most important points of this field within my literal review. The main goal of this study is to confirm or disprove some of the hypothesis in my breeding of Scarlet-chested Parrots (Neophema splendida). The research took three years and despite considerable domestication the sex ratio manipulation was proved in this species. Results show that the main factor affecting sex ratio was photoperiod during the breeding season and order of nesting.
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Genetic and epigenetic acpects of sex determination
Janoušek, Bohuslav ; Hodurková, Jaromíra ; Žlůvová, Jitka ; Lengerová, Martina ; Hobza, Roman ; Nix, Tomáš ; Vyskot, Boris
The article concentrates on the latest knowledge concerning the role of epigenetic mechanisms in sex determination in model dioecious species Silene latifolia. Results suggest that the locus suppressing development of female organs in male plants is hypersensitive to the action of agents influencing level of DNA methylation (5-azacytidine) and histone acetylation (trichostatin A). According to the results obtained via inter-specific hybridisation and the ability of the smut Ustilago violacea to activate development of male organs in female plants, it can be deduced that there is a locus suppressing male organ development in standard female plants. Function of this locus is not influenced by the drugs mentioned above.
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