( Suppressing colony formation is a us...)Marine phytoplankton changes form to protect itself from different predators

Suppressing colony formation is a useful strategy against copepods because they prefer to eat colonies of phytoplankton. A tiny single-celled organism that plays a key role in the carbon cycle of cold-water oceans may be a lot smarter than scientists had suspected.

In a paper published June 11 in the online version of Proceedings of the National Academy of Sciences, researchers report the first evidence that a common species of saltwater algae – also known as phytoplankton – can change form to protect itself against attack by predators that have very different feeding habits. To boost its survival chances, Phaeocystis globosa will enhance or suppress the formation of colonies based on whether nearby grazers prefer eating large or small particles.

“Based on chemical signals from attacked neighbors, Phaeocystis globosa enhances colony formation if that’s the best thing to do for survival, or it suppresses the formation of colonies in favor of growing as small solitary cells if that’s the best thing to do,” said Mark E. Hay, Teasley Professor of Biology at the Georgia Institute of Technology. “These changes in form made nearly a 100-fold difference in the alga’s susceptibility to being eaten. It’s certainly surprising that a single-celled organism can chemically sense the presence of nearby consumers, identify those consumers and change in opposing ways depending on which consumers are present.”

The behavior could have implications for global climate change because Phaeocystis blooms play a key role in the carbon cycle of cold oceans, accounting for up to 85 percent of local productivity during some time periods. This complex defensive behavior also shows how environmental factors can affect even simple organisms, Hay noted.
Phaeocystis suppresses colony formation in the presence of chemical signals from copepods and remains
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Source:Georgia Institute of Technology Research News