Earliest complex organisms fed by osmosis more than 540 mln yrs ago

Washington, August 20 (ANI): Scientists at Virginia Tech has shown that the oldest complex life forms, which lived in nutrient-rich oceans more than 540 million years ago, likely fed by osmosis.

The researchers studied two groups of modular Ediacara organisms, the fern-shaped rangeomorphs and the air mattress-shaped erniettomorphs.

These macroscopic organisms, typically several inches in size, absorbed nutrients through their outer membrane, much like modern microscopic bacteria.

The rangeomorphs had a repeatedly branching system like fern leaves and the erniettomorphs had a folded surface like an inflated air mattress to make tubular modules.

"These organisms are unlike any life forms since and so are poorly understood," said Marc Laflamme, who did the research as a postdoc in scientist Shuhai Xiao's lab at Virginia Tech.

The researchers decided to simulate various morphological changes in the overall construction of the organisms to test whether it would have been possible for them to attain surface area to volume ratios on the same order as modern bacteria that feed by osmosis.

"Modeling efforts suggest that internal vacuoles - that is, voids filled with fluids or other biologically inert materials - are a particularly effective way of increasing surface-to-volume ratio of complex, macroscopic organisms," said Michal Kowalewski, professor of geobiology in the College of Science at Virginia Tech.They discovered that the two groups (the repeatedly branching rangeomorphs and the air-mattress like erniettomorphs) grew and constructed their bodies in different ways.

However, both groups attempted to maximize their surface-area to volume ratios in their own way.

"The increase in size was clearly accomplished primarily by addition of modules for the erniettomorphs and repetitive branching and inflation of modules for the rangemorphs," Laflamme said.

"The repeated branching system in rangeomorphs was essential to allow for a high surface-area to volume ratio necessary for proper osmosis-based feeding," he added.

"We believe the Ediacarans were feeding on dissolved organic carbon, which can come in many forms," he said.

According to Laflamme, "There is a growing body of evidence that in Ediacaran times, due mainly to the absence of animals with true guts capable of packaging organic matter into fecal pellets, there was a much greater pool of dissolved organic nutrients, especially in deeper waters."

"Without fecal pellets, organic substances would have remained in suspension and decomposed into fats and proteins capable of dissolution into marine waters," he said.

"We believe these compounds were then absorbed via osmosis through Ediacaran "skin" due to the high surface-area to volume ratios," he added. (ANI)