How single-celled organisms navigate to oxygen

December 2, 2016, University of Cambridge
How single-celled organisms navigate to oxygen
Colonies of choannaflagellates. Credit: Raymond Goldstein

A team of researchers has discovered that tiny clusters of single-celled organisms that inhabit the world's oceans and lakes, are capable of navigating their way to oxygen. Writing in e-Life scientists at the University of Cambridge describe how choanaflagellates, the closest relatives of animals, form small colonies that can sense a large range of concentrations of oxygen in the water. The research offers clues as to how these organisms evolved into multi-cellular ones.

Although the single-celled ancestors of animals are extinct, the choanoflagellates, which evolved from a and which have remained single-celled since the Cambrian period around 500 million years ago, are common in the Earth's oceans and lakes. Certain choanoflagellate species form small swimming and these colonies are thought to resemble the early multicellular organisms that later evolved into animals. Oxygen levels on the planet started rising in the pre-Cambrian period and it's likely this played a major influence on the emergence of these multicellular life forms.

The researchers observed choanoflagellate colonies swimming under controlled conditions and varied the concentration in the water over time. They found the colonies navigate based on the logarithm of the , similar to the way humans sense sound and light. This increases their sensing capabilities in low-oxygen environments where navigation becomes crucial for survival.

One of the authors on the paper, Professor Raymond E. Goldstein, of the University's Department of Applied Mathematics and Theoretical Physics, says:

"Our work provides the first evidence that choanoflagellates can sense, and move towards, oxygen. 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 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."

Many organisms find their way to favourable areas by using different strategies. Bacteria bias their tumbling to navigate towards food and algae can turn and move directly towards light. While choanaflagellates require oxygen, it wasn't known if they could successfully navigate towards it. But the research showed both single cells and swimming colonies were able to find it.

While animals require enormous amounts of coordination between their cells in order to navigate, this research reveals such coordination isn't needed for simple multicellular life forms. In addition, microorganisms' search for food is rendered more difficult by the presence of thermal noise. Being so small, microorganisms are constantly being buffeted by vibrations in the waters that surround them, and their search strategy needs to be robust to counter this.

Explore further: Researchers find bacteria causes a single celled organism to form colonies

More information: Julius B Kirkegaard et al. Aerotaxis in the closest relatives of animals, eLife (2016). DOI: 10.7554/eLife.18109

Related Stories

A short jump from single-celled ancestors to animals

October 13, 2016

The first animals evolved from their single-celled ancestors around 800 million years ago, but new evidence suggests that this leap to multi-celled organisms in the tree of life may not have been quite as dramatic as scientists ...

Recommended for you

How birds and insects reacted to the solar eclipse

November 14, 2018

A team of researchers with Cornell University and the University of Oxford has found that birds and insects reacted in some surprising ways to the 2017 U.S. total solar eclipse. In their paper published in the journal Biology ...

Symbiosis a driver of truffle diversity

November 14, 2018

While the sight of black or white truffle being shaved over on pasta is generally considered a sign of dining extravagance, they play an important role in soil ecosystem services. Truffles are the fruiting bodies of the ectomycorrhizal ...

Gene-edited food is coming, but will shoppers buy?

November 14, 2018

The next generation of biotech food is headed for the grocery aisles, and first up may be salad dressings or granola bars made with soybean oil genetically tweaked to be good for your heart.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.