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Phytoplankton change form to escape predators with different feeding habits
June 16 : Marine phytoplankton change form to protect themselves against attack from predators who have very different feeding habits, according to a new study published online in this week’s Proceedings of the National Academy of Science (PNAS).
They either enhance or suppress the formation of their colonies depending on whether the predator prefers eating large or small particles.
“Based on chemical signals from attacked neighbours, Phaeocystis globosa enhances colony formation if that’s the best thing to do for survival, or it suppresses the formation of colonies in favour 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 make nearly a 100-fold difference in the algae’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,” he said.
Phaeocystis has two primary predators: small grazers such as ciliates, which prefer to eat small solitary cells that are four to six microns in diameter, and the larger shrimp-like copepods, which prefer to eat large, ball-shaped colonies.
When copepods are attacking the phytoplankton, the best survival strategy of Phaeocystis is to form solitary cells. When ciliates are attacking, they form colonies that are too large for those predators to consume.
According to Prof. Hay, the change in size difference of the colonies as a result of the chemical change can be dramatic.
“When one of these cells changes to the biggest colony form, although it takes a while, it’s like changing from a mosquito to 76 blue whales or 3,000 bull elephants. That’s a pretty dramatic difference,” he said. (ANI)
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