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Growth and ontogeny of sexual size dimorphism in Cetoniinae (Coleoptera: Scarabaeidae)
Vendl, Tomáš ; Šípek, Petr (advisor) ; Saska, Pavel (referee)
6 Abstract Due to its effect on fitness and many biological processes is body size one of the most important attribute of organisms. Body size is positively correlated with fecundity in insects and other ectotherms. Growth, which determine body size, is therefore crucial feature of animals. Study of growth can elucidate some aspects of body size evolution. Unfortunatelly, many insects life-history studies do not consider its complexity, especially the existence of distinct larval instars. Inaccurate record of growth trajectory may result also in biased differences in growth between sexually dimorphic sexes. Aim of this thesis is to record growth trajectories of two flower beetle species (Coleoptera: Scarabaeidae: Cetoniinae). These growth trajectories enable to define proximate mechanisms of growth with regard to individual instars. Determination of developmental mechanisms of sexual size dimorphism is another goal of this study. The growth is clearly divided in three distinct periods. In each individual period (i.e. instar) is described by asymptotic curve. The instars are not independent on each other - the growth in following instar is influenced by growth in previous. There are no differences in growth characteristics between sexes. Sexual size dimorphism is caused by differences in growth rate between...
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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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Growth and ontogeny of sexual size dimorphism in Cetoniinae (Coleoptera: Scarabaeidae)
Vendl, Tomáš ; Šípek, Petr (advisor) ; Saska, Pavel (referee)
6 Abstract Due to its effect on fitness and many biological processes is body size one of the most important attribute of organisms. Body size is positively correlated with fecundity in insects and other ectotherms. Growth, which determine body size, is therefore crucial feature of animals. Study of growth can elucidate some aspects of body size evolution. Unfortunatelly, many insects life-history studies do not consider its complexity, especially the existence of distinct larval instars. Inaccurate record of growth trajectory may result also in biased differences in growth between sexually dimorphic sexes. Aim of this thesis is to record growth trajectories of two flower beetle species (Coleoptera: Scarabaeidae: Cetoniinae). These growth trajectories enable to define proximate mechanisms of growth with regard to individual instars. Determination of developmental mechanisms of sexual size dimorphism is another goal of this study. The growth is clearly divided in three distinct periods. In each individual period (i.e. instar) is described by asymptotic curve. The instars are not independent on each other - the growth in following instar is influenced by growth in previous. There are no differences in growth characteristics between sexes. Sexual size dimorphism is caused by differences in growth rate between...
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