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The Lakeland Times | Minocqua, Wisc.

Jim Tait 02/01-02/28/17

home : outdoors : outdoors August 23, 2017

8/11/2017 7:25:00 AM
the lake where you live
Green galaxies
Ted Rulseh
Columnist

It's interesting in nature how simple creatures form complex societies. Ants, for example, cooperate to build elaborate nests in and above the ground. Honey bees fashion combs of hexagonal cells to feed and raise their young, and they do intricate dances to tell their hive-mates where to locate flowers and nectar.

Now, looking to your lake, what would you think of individual green algae cells arranged in a cluster and able to move, synthesize food, and even reproduce as a single organism? That's Volvox, a form of colonial algae (sometimes called globe algae). It might not exist in your lake - it's pretty much confined to bodies of clean water rich in nutrients (eutrophic).

Regardless, it's a fascinating life form. When I see a picture of a magnified Volvox colony (they are tiny, barely visible if at all to the unaided eye), for some reason I'm reminded of the Death Star from Star Wars. A more appropriate analog, though, would be a galaxy of green stars.

A Volvox colony consists of about 500 to several thousand algae cells arranged around the surface of a gelatin-like hollow sphere. Each individual cell has two whip-like structures (flagella) for mobility, several fluid-regulating organs (vacuoles), a chloroplast that makes food by way of photosynthesis, and an eyespot for detecting light.

The cells are connected by strands of cellular material (cytoplasm) so that they can chemically communicate, enabling the colony to "swim" in a coordinated manner, spinning on its way, propelled through the water by the flagella. The colonies are structured so cells with large eyespots are clustered at one side to facilitate movement toward sunlight for food production. Specialized reproductive cells are located on the opposite side.

And reproduce they do - entire colonies, not just individual cells. In fact, Volvox can reproduce sexually and asexually. For asexual reproduction, the colonies contain spherical daughter colonies. These emerge as new colonies when the parent colony dissolves. For sexual reproduction there are, believe it or not, male and female colonies, each with different germ cells. The male colonies have sperm cells, and the females have germ cells that enlarge to form an ovum (egg).

The flagella on the individual cells help the colony locate essential nutrients like phosphorus and nitrogen that can be absorbed to promote growth and reproduction. While creating their own food, Volvox colonies in turn become food for tiny animals (zooplankton) like rotifers and water fleas. In this way they start the food chain that ultimately leads to large predator fish like walleyes, bass and northern pike.

You won't see Volvox in your lake even if it's there; to do so you'd need to take a water sample and search it with a microscope. It's interesting, though to know these algal galaxies are out there, steadily swimming their way toward the light.

Ted Rulseh, who lives on Birch Lake in Harshaw, is the author of "The Lake Where You Live," a blog where readers can learn about the lakes they love - the history, geology, biology, chemistry, physics, magic, charm. Visit lakewhereyoulive.blogspot.com. Ted may be reached at trulseh@tjrcommunications.com.





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