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Symbiosis as a model for a new biology
Lhotský, Josef ; Markoš, Anton (advisor) ; Černý, Robert (referee)
Contemporary biology belongs among the most diversified sciences; yet one of its most fundamental and controversial questions is surprisingly: "What is life?". The aim of this study is to point out that biology is special among other natural sciences because its need of the notion of meaning. Meaning takes the central position in the biological rea-soning. Compared to other sciences, biology has to reflect the dimension of information and its interpretation: language-like properties, communication and interpretation belong to the basic characteristics of life. In spite of the fact, most contemporary theories of evo-lution deny active participation of living beings on the very process - living being come out of its description as puppets or zombies controlled by external forces. As a remedy from such a situation, biology should start with a new model for living entities. A bene-ficial methapor seems to be that of natural languages, i.e. an analogy between a net of historical interactions and conventional ways of interpretation of meaning in (i) living entities and (ii) in system of natural languages. I consider as the most appropriate biolo-gical systems for modeling of such a network of symbiotic interactions, i. e. the pheno-menon of symbiosis and especially symbiogenesis. Keywords: life,...
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Early craniofacial and dental morphogenesis in bichir, P. senegalus
Kráľovič, Martin ; Buchtová, Marcela (referee) ; Černý, Robert (advisor)
Polypterid fishes are considered the basal-most group of extant actinopterygians and thus may serve as a direct link for understanding the evolution of the first bony fishes. Their embryonic and larval material, however, is extremely scarce what makes it difficult to study their developmental patterns and processes. This work of mine is based on several successful breedings of the bichir Polypterus senegalus that allowed me to analyse development of some 70 specimens at key developmental stages. I have focused my attention to the early morphogenesis of teeth and dentition on several locations within a developmental context of oropharyngeal cavity. Oropharyngeal cavity develops quite differently when compared to other vertebrate species: it arises by means of a schizocoeliclike split of epithelial layers and, moreover, the earliest mouth cavity seems to be strongly constrained by the presence of cement (attachment) glands. Mouth opening proceeds by development of new, enigmatic structures that I have entitled the epithelial bridges (Kralovic et al., 2009) and that might represent the ectoderm-endoderm border often judged to be essential for tooth initiation and patterning. I have described a pronounced delay in initiation of pharyngeal teeth when compared to the oral teeth, probably as a direct consequence...
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Evolution of photoreceptors: insights from amphioxus
Vopálenský, Pavel ; Kozmik, Zbyněk (advisor) ; Černý, Robert (referee) ; Markoš, Anton (referee)
The topic of eye evolutionwas touchedas early as at the very beginningof the evolutionarytheoryitself.In his book'On theOrign of Species'CharlesDarwinexpresses concemsfor theexplanationof theocclurenceof complexeyesby naturalselection.Eventhe simplest'proto-eye'composedof a singlephotoreceptorcellanda shadingpigmentrequires properfrrnctioningof dozensof genesinvolvedin the phototansductioncascade,signal transmissionand pigmentation.Photoreceptorcells can be classifiedaccordingto their morphology as ciliary or rhabdomeric.Primary observationsrevealedthe rhabdomeric photoreceptorsbeing predominantlypresentin the eyes of invertebrates,whereasthe vertebrateandcnidarianseyesemploytheciliary type.Key componentsof thephotoreceptor cells arevisualpigments(opsins)andassociatedGa subunitsresponsiblefor absorptionof photonandthefirst stepof aphotoffansductioncascade.To properlyorchesftatetheassembly of thesestructuralgenesmediatingbiochemicalprocessesinto a functionalorgan,a tight regulationby a dedicatedsetof tanscriptionfactorsis required.Oneof themostremarkable andbeststudiedexamplesof geneswith anevolutionaryconservedrole in eyeorganogenesis is a paired-homeoboxgenePax6.However,availableliteraturepointsto othertranscription factors participatingin photoreceptordevelopmentacrossanimal phyla, for examplea...
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Oral morphogenesis in the Mexican axolotl: developmental origin of tooth germs in evolutionary contexts
Soukup, Vladimír ; Černý, Robert (advisor) ; Slípka, Jaroslav (referee)
Mouth in the majority of vertebrates develops throughout an ectodermal stomodeum which posteriorly contacts the foregut endoderm, together forming an oropharyngeal membrane. This ecto-/ endodermal membrane gradually thins and become eventually perforated, which causes opening of the stomodeal cavity into the pharynx. Teeth are then understood as organs arising within the stomodeal part of the mouth, where the ectodermal epithelium produces tooth enamel and neural crest mesenchymal cells form dentine and tooth pulp. This project was meant to study the dynamics of the ectoderm and endoderm during the formation of mouth and teeth in the Mexican axolotl. By utilizing transplantations of the oral ectoderm from GFP-transgenic embryos and injections of fluorescent tracer DiI into the endoderm, it was possible to follow the fate of both germ-layers during the course of embryonic development into details. By using this approach it was demonstrated that the mouth in the axolotl develops in a different way, i.e. via the stomodeal collar. Teeth were found to arise within the stomodeal collar ectoderm as well as in the more posteriorly situated endodermal areas. Moreover, some tooth germs were generated also directly at the ecto-/ endodermal boundary. Thus, the formation of teeth does not seem to primarily...
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