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Sperm competition in frogs in relation to the reproductive strategy
Malečková, Vendulka ; Šandera, Martin (advisor) ; Hortová, Kateřina (referee)
2 Abstract This bachelor thesis focuses the comparison of the various reproductive strategies of frogs and the degree of sperm competition. Frogs are ecologically important group inhabiting all continents except Antarctica and northern polar regions. Frogs have species-specific reproductive strategies. Most frogs have external fertilization, but there are exceptions (eg. Ascaphidae) with internal fertilization. Before mating occurs, male grips female - this is called amplexus. Amplexus is divided into several types according to the place of gripping the female, and there are exceptions that do not use amplexus. Even for them there is a complex behavior, in which the male directs the female to the eggs laying spot. Mating mostly occurs in water. Frogs are polyandrous, meaning that one female mates with multiple males. Such a system encourages the male-male competition, as well as the sperm-competition. Breeding of frogs can be classified as explosive or prolonged. Clutches of eggs are being laid by females into water or foam nests. In some cases the male takes part in taking care of the clutch, nest building, or they steal other clutches. In conclusion, it is discussed whether there is a connection between specific reproductive strategies and levels of sperm competition. Key words: amplexus, clutch-piracy,...
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Role of tetraspanin network during sperm-egg interaction and fusion
Černá, Pavlína ; Hortová, Kateřina (advisor) ; Petelák, Aleš (referee)
Fusion of sperm and egg is a crucial moment of the fertilization process which is fundamentally urged by tetraspanin superfamily proteins whose interactions allow mutual interaction of gamets and their subsequent fusion. Tetraspanins are 25-50 kD transmembrane proteins whose various kinds are found in most mammalian cells. Four transmembrane domains containing key amino acid residues indicating their function are their specificity. The essential feature of tetraspanins is their ability to form membranes lateral bonds which are reached thanks to large complexes with other proteins that form the so-called tetraspanin network. The interaction with other proteins and tetraspanins is important for a cell adhesion to the extracellular matrix, adhesion to the other cells, and it plays a role in signal transduction. This bachelor thesis describes and summarizes the role of tetraspanin networks during fusion of egg and sperm. A general introduction of tetraspanins, their structure and functions in cellular processes and interactions leading to the formation of tetraspanin networks which are the key point in fertilization, are given. A description of the fertilization process itself, the protein interactions and changes which precede it in included. The latest findings of the topic from the viewpoint of...
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Reproductive and epigenetic parameters in sperm connected to the disruptive development and early embryo loss.
Flintová, Jennifer ; Hortová, Kateřina (advisor) ; Petelák, Aleš (referee)
DNA methylation, histone modifications and regulation by non-coding RNAs are considered to play vital role in embryonal development and gametogenesis. Epigenetic mechanisms are not only inwardly programmed, but are massively affected by numerous exogenous aspects. Environmetal pollution and unhealthy parental lifestyle are two major factors related to impaired fertility status, abberant embryonal development of progeny. Some altered epigenetic marks can be transmitted to offspring generations, however in some cases these aberrations may be reversed by adequate lifestyle interventions. Since epigenetic regulations and genes responsible for spermatogenesis are conserved among vertebrates, studies based on animal models are highly relevant for understanding mechanisms causing impaired fertility and overall health in humans. Key words: Epigenetics, sperm, endocrine disruptors, hypoxia, lifestyle, transgenerational effect.
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