Researchers used the Mississippi alligator to investigate how fluctuations in the oxygen content of the Earth's atmosphere could have affected dinosaurs.
The lower the oxygen content of the air, the smaller the Dino? To these findings, American researchers have come through experiments with alligators. Background of the investigation: While the dinosaurs inhabited the earth, the oxygen content of the atmosphere fluctuated again and again. So he was at the first appearance of dinosaurs with twelve percent extremely low. The scientists therefore wondered how the giants developed under these circumstances, and resorted to a trick: They set eggs of alligators, descended from the same ancestors as the giant lizards, an extremely low oxygen content. The hatched pups were smaller and grew slower, while the heart and lungs were greatly enlarged. Similarly, the dinosaurs are likely to have adapted, the researchers report Tomasz Owerkowicz from the University of California in Irvine. Over the past 540 million years, the oxygen content of the Earth's atmosphere has fluctuated again and again until it levels off at the current 21 percent. To check how the fluctuating numbers impacted the dinosaurs, scientists focused on alligators. Like the dinosaurs, these "living fossils" belong to the group of archosaurs and are regarded as the closest living relatives besides the birds.

The researchers collected eggs from the Mississippi alligator (Alligator mississippiensis) and distributed them to three incubators. The oxygen content in the boxes was twelve, twenty-one, or thirty percent. The hatched pups differed massively from each other in body size and weight: The higher the oxygen content in the incubator, the bigger and heavier were the small lizards? a trend that continued during the further rearing under the same conditions.

The alligators, who had only twelve percent oxygen available, also had an enormously swollen yolk sac, an organ that feeds embryos of egg-laying vertebrates in the first few weeks. Due to this yolk sac, the animals only started eating a good week later than the other lizards.

The internal organs of the alligators had also adapted to the different oxygen levels: Little oxygen allowed the heart and lungs to grow so that the animals could absorb as much of the rare element as possible. Nevertheless, these alligators needed to breathe significantly more often to meet their oxygen needs. The liver and stomach, on the other hand, were smaller in these lizards. This allowed them to eat less, which is why they also showed the lowest metabolic rate. Conversely, the researchers measured the lowest respiratory and the highest metabolic rate in the lizards, which had thirty percent oxygen available. display

Tomasz Owerkowicz (University of California, Irvine) et al .: The Journal of Experimental Biology, Vol. 212, p. 1237, doi: 10.1242 / jeb.023945 ddp / science.de? Masha's shaft

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