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The effect of incubation temperature on cognition and brain cellular composition in geckos Paroedura picta
Polonyiová, Alexandra ; Němec, Pavel (advisor) ; Sedláček, František (referee)
The effect of incubation temperature on different morphological, physiological, cognitive and behavioral characteristics in reptiles is a well-studied topic, although the underlying mechanism leading to the differences between individuals incubated at different temperatures remains largely unknown. In this thesis I studied the effect of incubation temperature on cognitive abilities and the number of neurons and non-neuronal cells in the gecko Paroedura picta incubated at two different temperatures, 24řC and 30řC. The geckos were tested in two cognitive tasks with simulated predatory attack. 14-day-old hatchlings were tested in a Y-maze, while 6-months-old geckos were tested in an arena with shelters of different colors. After testing, the number of neurons and non- neuronal cells in several parts of the brain were estimated using the isotropic fractionator in selected individuals. Although incubation temperature did not affect the success in the cognitive task in hatchlings, it did affect the total time needed to find the shelter. This difference remained significant also in adult geckos. The number of neurons, which was used as a proxy for the information processing capacity of the brain, did not affect success in the cognitive tasks. However, absolute brain size correlated with success in 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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