Marine plants can flee to avoid predators, researchers say

September 28, 2012

Scientists at the University of Rhode Island's Graduate School of Oceanography have made the first observation of a predator avoidance behavior by a species of phytoplankton, a microscopic marine plant. Susanne Menden-Deuer, associate professor of oceanography, and doctoral student Elizabeth Harvey made the unexpected observation while studying the interactions between phytoplankton and zooplankton.

Their discovery will be published in the September 28 issue of the journal .

"It has been well observed that can control their movements in the water and move toward light and ," Menden-Deuer said. "What hasn't been known is that they respond to predators by swimming away from them. We don't know of any other plants that do this."

While imaging 3-dimensional predator-prey interactions, the researchers noted that the phytoplankton Heterosigma akashiwo swam differently in the presence of predators, and groups of them shifted their distribution away from the predators.

In a series of , Menden-Deuer and Harvey found that the phytoplankton not only flee when in the presence of the predatory , but they also flee when in water that had previously contained the predators. They found only a minimal effect when the phytoplankton were exposed to predators that do not feed on phytoplankton.

"The phytoplankton can clearly sense the predator is there. They flee even from the chemical scent of the predator but are most agitated when sensing a feeding predator," said Menden-Deuer.

When the scientists provided the phytoplankton with a refuge to avoid the predator – an area of low salinity water that the predators cannot tolerate – the phytoplankton moved to the refuge.

The important question these observations raise, according to Menden-Deuer, is how these interactions affect the survival of the .

Measuring survival in the same experiments, the researchers found that fleeing helps the alga survive. Given a chance, the predators will eat all of the phytoplankton in one day if the algae have no safe place in which to escape, but they double every 48 hours if they have a refuge available to flee from predators. Fleeing makes the difference between life and death for this species, said Menden-Deuer.

"One of the puzzling things about some phytoplankton blooms is that they suddenly appear," she said. "Growth and nutrient availability don't always explain the formation of blooms. Our observation of algal fleeing from predators is another mechanism for how blooms could form. Amazingly, looking at individual microscopic behaviors can help to explain a macroscopic phenomenon."

The researchers say there is no way of knowing how common this behavior is or how many other species of phytoplankton also flee from , since this is the first observation of such a behavior.

"If it is common among phytoplankton, then it would be a very important process," Menden-Deuer said. "I wouldn't be surprised if other species had that capacity. It would be very beneficial to them."

In future studies, she hopes to observe these behaviors in the ocean and couple it with genetic investigations.

Explore further: Variable light illuminates the distribution of picophytoplankton

More information: dx.plos.org/10.1371/journal.pone.0046438

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3 comments

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Telekinetic
1 / 5 (8) Sep 28, 2012
"The researchers say there is no way of knowing how common this behavior is or how many other species of phytoplankton also flee from predators, since this is the first observation of such a behavior."- article
Ah, so these researchers were the first to observe this behavior finally after hundreds of thousands of years of underwater swimming by humans. Also, what this article reinforces, not discovers, is that plants have consciousness. I am not saying that they have emotions as we know them, but a survival response that had been documented years ago.
unknownorgin
1 / 5 (1) Sep 29, 2012
If it moves by choice on its own power how can it be a plant? A plantimal maybe?
ValeriaT
not rated yet Sep 29, 2012
You see, even these microscopic cells can feel a fear like the higher animals.. Heterosigma itself can be dangerous for aquatic cultures and it kills the farmed fish.

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