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. displayTomasz 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