平特五不中

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Researchers at 平特五不中 published in the journal Nature, turned to a living fish, called Polypterus, to help show what might have happened when fish first attempted to walk out of the water. Polypterus is an African fish that can breathe air, 'walk' on land, and looks much like those ancient fishes that evolved into tetrapods. The team of researchers raised juvenile Polypterus on land for nearly a year, with an aim to revealing how these 'terrestrialized' fish looked and moved differently.
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鈥淪tressful environmental conditions can often reveal otherwise cryptic anatomical and behavioural variation, a form of developmental plasticity鈥�, says Emily Standen, a former 平特五不中 post-doctoral student who led the project, now at the University of Ottawa. 鈥淲e wanted to use this mechanism to see what new anatomies and behaviours we could trigger in these fish and see if they match what we know of the fossil record.鈥�
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Remarkable anatomical changes

The fish showed significant anatomical and behavioural changes.听 The terrestrialized fish walked more effectively by placing their fins closer to their bodies, lifted their heads higher, and kept their fins from slipping as much as fish that were raised in water. 鈥淎natomically, their pectoral skeleton changed to become more elongate with stronger attachments across their chest, possibly to increase support during walking, and a reduced contact with the skull to potentially allow greater head/neck motion,鈥� says Trina Du, a 平特五不中 Ph.D. student and study collaborator.
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鈥淏ecause many of the anatomical changes mirror the fossil record, we can hypothesize that the behavioural changes we see also reflect what may have occurred when fossil fish first walked with their fins on land鈥�, says Hans Larsson, Canada Research Chair in Macroevolution at 平特五不中 and an Associate Professor at the Redpath Museum.
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Unique experiment

The terrestrialized Polypterus experiment is unique and provides new ideas for how fossil fishes may have used their fins in a terrestrial environment and what evolutionary processes were at play.
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Larsson adds, 鈥淭his is the first example we know of that demonstrates developmental plasticity may have facilitated a large-scale evolutionary transition, by first accessing new anatomies and behaviours that could later be genetically fixed by natural selection鈥�.
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The study was conducted by Emily Standen, University of Ottawa, and Hans Larsson, Trina Du at 平特五不中.
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This study was supported by the Canada Research Chairs Program, Natural Sciences and Engineering Research Council of Canada (NSERC) and Tomlinson Post-doctoral fellowship.
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