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Primary mouth formation in basal fishes
Psutková, Viktorie ; Černý, Robert (advisor) ; Šindelka, Radek (referee)
The mouth is a crucial structure for every organism since it forms an important connection between internal and external environments. The primary mouth develops from the ectodermal-endodermal region at the anteriormost part of the forming head during early embryogenesis. In the majority of vertebrates the primary mouth develops through the stomodeal invagination, establishment of the oral membrane, and by its rupture the mouth gets opened. However, the mouth development significantly differs in several groups of vertebrates and the three main modes of the mouth development were recognized according to ectoderm-endoderm interactions. The most common is "stomodeal invagination", the "stomodeal collar" is in salamanders and lungfishes, and "stomodeal wedge" in teleosts. Here, I analyse the development of the oral region in embryos of basal actinopterygian fishes, bichir (Polypterus senegalus), sturgeon (Acipenser ruthenus) and gar (Atractosteus tropicus), which could give us better understanding of the evolution and morphogenesis of the primary mouth in vertebrates. In bichir embryos, the mouth development generally resembles development of the stomodeal wedge in teleost fishes, with some morphogenetic differences. In sturgeons, the mouth forms via modified stomodeal collar, whereas in gars the mouth...
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The embryonic formation of the primary mouth in vertebrates
Psutková, Viktorie ; Černý, Robert (advisor) ; Soukup, Vladimír (referee)
The primary mouth develops during early embryogenesis at the anterior end of the forming head and it is created from the ectoderm and the endoderm that directly juxtapose. The primary mouth is the first connection of the digestive system with the outside, which is undoubtedly a crucial step for further development of an organism. In most vertebrates, the primary mouth is getting opened by perforation of a thin septum, the oral membrane. The oral membrane is formed from the ectoderm and the endoderm, when the ectoderm pushes against endoderm. Surprisingly, developmental formation of the primary mouth is not identical in all vertebrates and we can commonly recognize three main developmental modes. In the most vertebrates clades, the primary mouth forms via the so called stomodeal invagination, which is often exemplified in the frog Xenopus leavis. The primary mouth of salamanders and lungfishes forms via the so called stomodeal collar and the primary mouth of teleost fishes forms via the so called stomodeal wedge. Moreover, in the hagfishes, the development of the primary mouth seems similar to the stomodeal invagination, but with some substantial differences in later formation. The particular mode of the primary mouth formation probably depends on the course of embryonic development and spatial...
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