Early-stage complex organisms fed by osmosis

Research at Virginia Tech has shown that the oldest complex forms of life - living in nutrient-rich seas over 540 million years ago - can be eaten by osmosis.

Scientists studied two groups of Edicara organisms, fern-shaped rangeomorphs and erniettomorphs that are air-shaped. These organisms, usually several inches in size, have absorbed nutrients through the outer membrane, like modern bacteria now, according to the number of days in the Proceedings of the National Academy of Sciences (PNAS) article (PNAS). August 25, 2009, "Osmotrophy in modular Edicara organisms," by Marc Laflamme, Shuhai Xiao, and Michal Kowalewski. Laflamme, now a postdoctoral researcher in the Department of Geophysics and Geology, yale University, conducted research in Xiao's lab at Virginia Tech. Xiao and Kowalewski are life professors at the College of Science, Virginia Tech University.

Rangeomorphs have a continuous branching system like fern leaves and erniettomorphs have a folded surface like an air cushion to create tubular modules. Laflamme said: 'These creatures are unlike any life form that has ever been known, and therefore understanding them is still very limited'.

The way they eat is a controversial topic, with hypotheses from parasite to symbiosis and even photosynthesis. "Many hypotheses can be eliminated because this organism has no structure to eat, such as tentacles or mouths, and most of them live in deep sea where there is no light for photosynthesis," Xiao said. '.

Charnia masoni, a rangeomorph species.(Photos: Wikipedia)

The researchers decided to simulate changes in the overall structure of the organism to test whether it is possible to achieve a 'surface area to volume' ratio similar to the current bacteria. Great feeding by osmosis. The theoretical models were developed to understand the effects of length, width, thickness, number of modules and the appearance of small internal niches for the surface area of ​​the pre-Cambrian fossil. Kowalewski said: 'The model-building efforts show that the small inner cavities - those that contain fluids or other biological materials - are an effective way to increase the ratio of' surface area to quantity '. 'of macro and complex organisms'.

They found that the two groups developed and built their bodies in different ways, but both groups tried to maximize the rate of 'surface area on quantity' in their own way. Laflamme said: 'Erniettomorphs gain size by adding tubular modules, while the rangemorphs achieve this by branching and flattening the module. A continuous branching system in the rangeomorphs is necessary to achieve a high 'surface area to volume' ratio, necessary for osmotic feeding mechanism '.

Today, only microbes appear to be effective in osmosis, although some animals, such as sponges and corals, use osmosis as an alternative food source. During Ediacaran, 635 to 541 million years ago, with a nutrient-rich ocean, the strategy of absorbing nutrients by diffusion seemed more effective.

Laflamme said: 'We believe that Ediacaran's creatures feed on decomposed organic carbon in many forms. It represents organic material derived from plants, fungi, and animals that break down into fats and proteins during natural organic decay. There is growing evidence that during Ediacaran's period, due to the absence of animals with the intestinal system capable of 'packing' organic matter into pellets, the amount of organic nutrients decomposed richly and densely. especially in deeper areas. There is no 'packaging' process, organic substances break down into fats and proteins that dissolve into seawater. We believe that these compounds are absorbed through the 'skin' of Ediacaran organism due to the 'high surface area' quantity '.

The article in PNAS concludes that today 'giant sulfur bacteria, such as Thiomargarita, live in coastal areas of Namibia, where access to more biodegradable organic nutrients and carbon. Such nutrient-rich areas may be typical of the Ediacaran period ocean, suggesting that it is not entirely coincidental that the first rangeomorphs appear in decomposing organic carbon-rich deep water. '

The study was conducted by Canada's Council for Natural Science and Technology Research (NSERC), and Laflamme's Bateman Foundation, NASA's Extraterrestrial Biology and Evolutionary Biology Program, and the Sediment and Ancient Geological Program. Biology National Science Foundation.

Refer:

Marc Laflamme, Shuhai Xiao, Michał Kowalewski.Osmotrophy in Ediacara organisms modular.Proceedings of the National Academy of Sciences, 2009;DOI: 10.1073 / pnas.0904836106