The rise of a shape-shifting animal revealed

An international group of scientists have determined how some of the first large organisms were able to change their body shape and size.

Known as rangeomorphs, the organisms could grow up to two metres in height by extracting nutrients from their environments, at a time when many other lifeforms were microscopic. Exhibiting the geometric shape of a fractal, they existed in oceans 635 to 541 million years ago in what is known as the Ediacaran period.

Dr Jennifer Hoyal Cuthill from the University of Cambridge and lead author of the study, said: “What we wanted to know is why these large organisms appeared at this particular point in Earth's history. They show up in the fossil record with a bang, at very large size. We wondered, was this simply a coincidence or a direct result of changes in ocean chemistry?”

The researchers used a wide array of mathematical and computer models, micro-CT scanning and photographic measurements to examine rangeomorph fossils from Canada, Australia and the UK. The analysis provides the earliest evidence for nutrient dependent growth – called ecophenotypic plasticity.

Dr Cuthill and her team suggest that rangeomorphs not only show a strong degree of this plasticity but that this provided a crucial advantage in a rapidly changing environment. An example would be rangeomorphs rapidly changing to become longer and tapered, to adjust to elevated levels of oxygen above them. Dr Cuthill said: “It's probably too early to conclude exactly which geochemical changes in the Ediacaran oceans were responsible for the shift to large body sizes, but there are strong contenders, especially increased oxygen, which animals need for respiration.” These results could help explain how organisms such as dinosaurs and blue whales could ultimately evolve.

The researchers believe the sudden appearance of large rangeomorphs could have been a direct result of major changes in climate and ocean chemistry. Late in the Ediacaran period, there seems to have been large-scale changes in the Earth’s oceans following an ice age known as the Gaskiers glaciation.

During this study, researchers from the University of Cambridge worked alongside scientists from the Tokyo Institute of Technology. It was published in Nature Ecology and Evolution.

https://www.youtube.com/watch?v=F48yZkdDV60