Phosphatized multicellular algae in the Neoproterozoic Doushantuo Formation, China, and the early evolution of florideophyte red algae
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Abstract:
Phosphatic sediments of the Late Neoproterozoic (ca. 600 million years old [Myr]) Doushantuo Formation at Weng'an, South China, contain fossils of multicellular algae preserved in anatomical detail. As revealed by light microscopy and scanning electron microscopy, these fossils include both simple pseudoparenchymatous thalli with apical growth but no cortex-medulla differentiation and more complex thalli characterized by cortex-medulla differentiation and structures interpretable as carposporophytes, suggesting a multiphasic life cycle. Simple pseudoparenchymatous thalli, represented by Wengania, Gremiphyca, and Thallophycoides, are interpreted as stem group florideophytes. In contrast, complex pseudoparenchymatous thalli, such as Thallophyca and Paramecia, compare more closely to fossil and living corallinaleans than to other florideophyte orders, although they also differ in some important aspects (e.g., lack of biocalcification). These more complex thalli are interpreted as early stem group corallinaleans that diverged before Paleozoic stem groups such as Arenigiphyllum, Petrophyton, Graticula, and Archaeolithophyllum. This phylogenetic interpretation implies that (1) the phylogenetic divergence between the Florideophyceae and its sister group, the Bangiales, must have taken place before Doushantuo time-an inference supported by the occurrence of bangialean fossils in Mesoproterozoic rocks; (2) the initial diversification of the florideophytes occurred no later than the Doushantuo time; and (3) the corallinalean clade had a "soft" (uncalcified) evolutionary history in the Neoproterozoic before evolving biocalcification in the Paleozoic and undergoing crown group diversification in the Mesozoic.Keywords:
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In order to provide the proof in molecular biology for the mosaic thalli of Porphyra yezoensis,the individual thallus is analyzed by the codominance of SSR.Sixty-five individuals of the thalli of P.yezoensis were analyzed with 5 microsatellite primers by PAGE electrophoresis.The results show that heterozygous individuals and pure individuals are both found with 41.5% are heterozygous,58.5% are pure.It increases the knowledge of mosaic thalli with cells of different genetic basis in P.yezoensis.During the extraction of DNA from the thalli of P.yezoensis,5M KAc was used to eliminate the remaining polysaccharides.The extracted DNA was of high quality and suitable for molecular analyses.
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Abstract The Structural Heterogeneity of Plants with a Thallus. Plants that evolved in aquatic environments developed a thallus, that is a multicellular body without structures deputed to the mass transportation of water along great distances. The structural organisations of thalli shows a number of different solution to reach the coordination necessary to the expression of differentiation in the multicellular thalli. Some of these structures are comparatively esamined, pointing out their peculiarities. The diversity observed among plants evolved in aquatic environments is expressed not only by the taxa that can be recognized, but also by a great number of solutions developed to express the differentiation of parts in a complex multicellular body. Key Words: flagellatesnanoplanktonMediterranean Sea
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Abstract The red seaweed Pyropia yezoensis is a marine crop of important economic value and is widely cultivated in the coastal areas of northern China. The current seedling-raising system relies on the germination of conchospores, a process not fast enough to meet the increasing demand from farmers. In this study, we developed a monospore-dependent seedling method based on the asexual reproduction of the Pyropia thallus. The Pyropia thallus was physically sectioned into small pieces (microthalli) that were cultivated at 15 °C. The algal cells in the microthalli became morphologically condensed, underwent cell division, and then developed into monospores on the 5th day. The monospores were able to attach to the seeding rope in 24 h and germinated into healthy thalli. To optimize the efficiency of monospore release, we tested the effect of temperature and the size and original positions of the microthalli as well as the age of the mother thallus. Microthalli with a size of 30–50 cells from the middle and apex of 21-day-old thalli cultivated at 15 ° C yielded the optimum production of monospores. Theoretically, in this thallus-to-thallus seeding strategy, 0.1 g of thallus could produce at least 10 7 monospores, with the same number of offspring thallus seedlings. Taking all of these advantages together, including the high efficiency, short time, low cost and easy operation, this physical sectioning method could serve as a promising seed source especially for new cultivars with superior traits in Pyropia farming and rapid replenishment of seedlings when thalli undergo disastrous diseases.
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