Study: Choanaflagellates navigate to oxygen

CAMBRIDGE, England, Dec. 2 (UPI) -- Single-celled organisms called choanaflagellates, the closest relatives of animals, can sense oxygen levels. The ability allows the organisms, which form small colonies, to navigate to areas richest in oxygen.

Choanoflagellates and animals evolved from a common ancestor some 500 million years ago during the Cambrian period. Animals, of course, went on to spawn a variety of complex life forms, while choanoflagellates remain single-celled.

The recent analysis of the simple single-celled organisms offers insight into how early life survived on Earth.

During a series of lab experiments, researchers at the University of Cambridge exposed choanoflagellate colonies to a variety of chemical conditions -- aqueous settings with varying levels of oxygen. The colonies showed the ability to seek out areas of higher oxygen, suggesting the organisms sense the logarithm of oxygen concentration.

In other words, the organisms have a sliding scale of oxygen levels built into their navigational hard wiring. The ability may explain the organisms' ancient success.

"Our work provides the first evidence that choanoflagellates can sense, and move towards, oxygen," Raymond E. Goldstein, a professor of applied mathematics and theoretical physics at Cambridge, said in a news release. "Since choanoflagellates are now understood to be the closest relatives of animals, this discovery may shed light on the properties of the last common ancestor of the two groups, and in particular its response to the changing oxygen levels in the Precambrian era."

"Perhaps more importantly, the work raises fascinating questions about how the simplest multicellular organisms, lacking any type of central nervous system, sense and respond to their environment," Goldstein added.

Scientists knew choanoflagellates need oxygen but weren't sure if the organisms could successfully seek it out. Choanoflagellates aren't the only single-celled organisms who use biochemical necessities as a navigational beacon. Bacteria travel towards sources of nutrients, while algae move in the direction of light.

Scientists published their choanoflagellates study in the journal eLife.