How Volvox got its groove

February 19, 2009
The colonial alga Volvox tertius has about 2,000 cells and a complete division of labor: cells either swim or reproduce, but not both. The few large cells within these colonies are the reproductive cells, while the many tiny cells do the swimming. Copyright 2009 Matthew Herron.

Some algae have been hanging together rather than going it alone much longer than previously thought, according to new research.

Ancestors of Volvox algae made the transition from being a single-celled organism to becoming a multicellular colony at least 200 million years ago, during the Triassic Period.

At that time, Earth was a hot-house world whose inhabitants included tree ferns, dinosaurs and early mammals. Previous estimates had suggested Volvox's ancestors arose only 50 million years ago.

The algae switched to a communal lifestyle in only 35 million years -- "a geological eyeblink," said lead researcher Matthew D. Herron of The University of Arizona in Tucson.

Pleodorina starrii has an incomplete division of labor. Although the 12 small cells near the top of this colony only swim, the 20 larger cells both swim and reproduce. Copyright 2008 Matthew Herron

Figuring out how algae made the leap can provide clues to how multicellular organisms such as plants and animals evolved from single cells.

Cooperating successfully is the key, Herron said.

"All the macroscopic organisms we see around us trace back to unicellular ancestors," said Herron, a doctoral candidate in the UA's department of ecology and evolutionary biology. "Each of those groups had to go through a transition like this one.

"We think the early changes in this process were related to cooperation among cells and conflicts among cells -- and finally to the resolution of those conflicts," he said.

The researchers used DNA sequences from about 45 different species of Volvox and related species to reconstruct the group's family tree and determine how long ago the first colonial ancestor arose.

The team's article "Triassic origin and early radiation of multicellular volvocine algae," is in this week's online Early Edition of the Proceedings of the National Academy of Sciences.

Herron's co-authors Jeremiah D. Hackett and Richard E. Michod are members of the UA's department of ecology and evolutionary biology. Co-author Frank O. Aylward was at the UA when the research was conducted and is now at the University of Wisconsin in Madison. The Society of Systematic Biologists and Sigma Xi helped fund the research.

Volvox and its relatives live in freshwater ponds all over the world. Some of the species are unicellular, while others live in colonies of up to 50,000 cells.

Many of the colonial algae species are visible to the eye and appear to be little green spheres rolling through the water. The most complex species have a division of labor -- some cells do the swimming, others do the reproducing.

Although an earlier estimate suggested the algae's ancestors banded together 50 million years ago, Herron wanted to check the estimate using 21st-century genetic and molecular techniques.

In addition to constructing the Volvox family tree, the team determined how long ago the group's oldest common ancestor lived by comparing the amount of genetic differences between species.

One of the earliest traits to evolve is the clear jelly-like substance visible between the cells of the spherical Volvox colonies, Herron said. "We think that stuff is what held the earliest multicellular colonies together."

Banding together in a larger mass can provide protection from predators, he said. "Some things can't eat you if you're bigger."

But producing the goo, called extracellular matrix, takes resources and is one of the costs of cooperation.

"So now there's a temptation to cheat," Herron said. "Let's say I'm in a four-cell colony. I'm going to let the other three guys make the extracellular matrix, and I'm going to focus on growing and reproducing. That's the conflict."

Overcoming that conflict is essential to becoming a multicellular organism, he said. The benefits of cheating have to be reduced for the cells to cooperate successfully.

Some traits the team studied are genetic traits that mediate conflict.

Genetic control of cell number is one of those, he said. "If my number of offspring is fixed at four, now there's no reason for me to cheat. I can't have eight offspring when everyone else is having only four."

Herron is now studying whether the size of the colony affects the degree to which there are different types of cells within the colony.

Source: University of Arizona

Explore further: Researchers build bacteria's photosynthetic engine

Related Stories

Researchers build bacteria's photosynthetic engine

July 29, 2015

Nearly all life on Earth depends on photosynthesis, the conversion of light energy into chemical energy. Oxygen-producing plants and cyanobacteria perfected this process 2.7 billion years ago. But the first photosynthetic ...

Plant light sensors came from ancient algae

July 28, 2015

The light-sensing molecules that tell plants whether to germinate, when to flower and which direction to grow were inherited millions of years ago from ancient algae, finds a new study from Duke University.

An algorithm to investigate unwelcome plankton

July 8, 2015

Computer scientists at Columbia University will work with oceanographers to understand what has caused an unusual plankton-like species to rapidly invade the Arabian Sea food chain, threatening fisheries that sustain more ...

A new timetable of eukaryotic evolution

June 2, 2015

Contaminated samples have evidently created some confusion in the timetable of life. On the basis of ultra-clean analyses, an international team, including scientists from the Max Planck Institute for Biogeochemistry, has ...

Spike in water toxins blamed for hundreds of turtle deaths

May 31, 2015

Hundreds of small turtles have washed up dead on the eastern end of Long Island in the last month, a die-off scientists blame on waterborne toxins that have reached unprecedented levels for reasons that aren't entirely clear.

Recommended for you

For 2-D boron, it's all about that base

September 2, 2015

Rice University scientists have theoretically determined that the properties of atom-thick sheets of boron depend on where those atoms land.

At Saturn, one of these rings is not like the others

September 2, 2015

When the sun set on Saturn's rings in August 2009, scientists on NASA's Cassini mission were watching closely. It was the equinox—one of two times in the Saturnian year when the sun illuminates the planet's enormous ring ...

10 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Velanarris
5 / 5 (1) Feb 19, 2009
NeilF is gonna be mad. Algae stole his company name.
nano999
not rated yet Feb 19, 2009
Haha! That's what I was thinkin'! Is that guy for real or what?
earls
1 / 5 (1) Feb 19, 2009
"what"
el_gramador
1 / 5 (1) Feb 19, 2009
You guys do realize that it's Vulvox, not Volvox right? I may not care about the site too much, but at the very least I know they sound different.
Velanarris
not rated yet Feb 20, 2009
You guys do realize that it's Vulvox, not Volvox right? I may not care about the site too much, but at the very least I know they sound different.

It's a joke made at the expense of a con artist who can't scratch together the $4 a year it costs for a proper domain registration. Comedic liberty.
Roach
not rated yet Feb 20, 2009
What is the deal with people on here taking all the jokes too seriously, first someone gets angry at me over praising our Hamster overlords, now a pun? I can't imagine how much fun these guys are over a beer.
Velanarris
1 / 5 (1) Feb 20, 2009
What is the deal with people on here taking all the jokes too seriously, first someone gets angry at me over praising our Hamster overlords, now a pun? I can't imagine how much fun these guys are over a beer.
They don't drink beer due to it's excessive CO2 outgassing when opened.
Birger
not rated yet Feb 21, 2009
Maybe simple algae living in clusters like this will be more tractable tools for genetic engineering ?
-Say you want an organism that absorbs pollutants, big plants have more complex genomes, making GM harder, and single unicellular algae are more vulnerable.
el_gramador
not rated yet Feb 23, 2009
I should've probably said this earlier but, what are we two-year olds? Snickering over a difference in spelling?
Velanarris
5 / 5 (1) Feb 24, 2009
I should've probably said this earlier but, what are we two-year olds? Snickering over a difference in spelling?
So how is working for Neil?

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.