For instance, how and why did multicellular life arise? To help answer that, Roper has been studying an organism in a family known as the choanoflagellates the closest single-celled cousins of multicellular animals. Scientists believe that something remarkable must have happened following the divergence of choanoflagellates from the multicellular animals to create conditions favoring complex multicellular life.
Interestingly, it was recently discovered that one species of the single-celled choanoflagellates Salpingoeca rosetta, which lives in muddy coastal areas and feeds on bacteria can form colonies ranging from two cells to a couple dozen. The discovery surprised Roper.
"It's like watching a fish walk onto land seeing evolution in action," he said. "If we can understand the conditions that make this transition occur, maybe we can understand why multicellularity arose among animals in the first place."
Is there any advantage to S. rosetta being mutlicellular? Roper found an answer in fluid dynamics. In research published recently in the journal Physical Review Letters, he and his colleagues report that multicellular S. rosetta colonies generate collective fluid flows that improve the cells' ability to feed.
A single cell's tail, or flagellum, allows the cell to swim and helps bring toward the cell fluid containing the bacteria on which it feeds. Generally, multicellular organisms can swim faster and therefore encounter more food.
But multicellular S. rosetta colonies seem, at first glance, to be less adept at these activities, Roper said. The colonies swim more slowly and poorly than single cells. The flagella of the cells extend in various directions, like a rowboat whose passengers steer their oars in different directions. So is there any benefit at all for these colonies?
Although this "multiple oars" chaos does hinder the colony's ability to
|Contact: Stuart Wolpert|
University of California - Los Angeles