Microscopic plankton are at the center of the ocean’s food chain, providing food for much larger animals like whales. However, little is known about how single-celled phytoplankton, most of which lack swimming appendages, migrate. They travel from the darkest and coldest depths of the ocean to the surface, only to drift away again. A type of bioluminescent phytoplankton called Pyrocystis noctiluca This is accomplished by inflating it to six times its normal size. This expansion allows plankton, typically just a few hundred microns wide, to rise about 656 feet toward the ocean’s surface, capturing sunlight and making food. For more information on this unique strategy for ocean travel, The study was published Oct. 17 in the journal Cell Press current biology.
“In this paper, we discovered that P. noctiluca “Cells are like little submarines, and we can control their density very precisely, so we can choose where we want to be in the water column,” said study co-author, a marine biologist and bioengineer at Stanford University. says Manu Prakash. said in a statement.
[Related: NASA’s PACE satellite takes off to monitor phytoplankton—from space.]
On average, phytoplankton 5-10% heavier than seawater. This means they have to contend with gravity if they want to stay at sea surface for photosynthesis.
Prakash and study co-author Adam Larson, a postdoctoral fellow at Stanford University, witnessed Adam Larson bloom while on a research vessel off the coast of Hawaii. P. noctiluca. To their surprise, the net contained two types of plankton of different sizes.
“It took us a while to figure out why until we videotaped the cells undergoing this massive expansion.” Larson said in a statement:. “It can happen very suddenly, so if you’re asleep next to the microscope for 10 minutes, you might miss it.”
in studythey tested how this rapid growth affects plankton. To do this, they developed a tool called the gravity machine.
“Using gravity machines, we can see single cells in an infinite water column at subcellular resolution,” says Prakash. “It’s a bit like a Ferris wheel for gerbils or rats, but with just one cell. It’s about the size of a dinner plate and spins, so the cell knows it’s not rising or sinking within its own frame of reference. I don’t know.
Change the pressure and density of water in a gravity machine Creates a virtual reality environment that mimics the deep ocean. Using this machine, the researchers found that the expanded cells were less dense than the surrounding seawater. This allows it to escape the downward pull of gravity and float toward a virtual surface.
a look closely showed that this expansion occurs as a natural part of the planktonic cell cycle. After single-celled plankton split into two, internal structures called vacuoles filter through fresh water. This will significantly increase the size of the two new cells. The two daughter cells swell with light fresh water and sail upward.
of Pyrocystis Cell cycle. Part 1 shows the life cycle of Pyrocystis. Part 2 shows how the cell wall breaks down. Part 3 shows how the cell expands. Part 4 details the dynamics that occur within the cytoplasm after division. Credit: Larson et al./Current Biology
video: Pyrocystis Cell cycle. Part 1 shows the life cycle of Pyrocystis. Part 2 shows the destruction of the cell wall. Part 3 shows how the cell expands. Part 4 details the dynamics that occur within the cytoplasm after division. Credit: Larson et al./Current Biology
“What we realized is that this is a very clever way to essentially play slingshot in the ocean during cell division,” Prakash said. “So, what happens in normal times? We produce a lot of protein, we get a lot of sunlight, and we produce a lot of biomass until our bodies become so heavy that we sink. Next, we go to the deep sea and undergo cell division. and uses expansion to return to its mother’s size.
this The entire cell cycle takes about 7 days And that coincides with the time when plankton begin to ascend in search of sunlight and nutrients. According to PrakashThis may be the first clear evidence that this cell cycle is controlled by ecological parameters.
“All cells experience the downward pull of gravity, and unless they and their descendants fight back, they’ll fall into a gravitational trap and sink to the bottom of the ocean forever,” said study co-author and Stanford University professor. said postdoctoral researcher Rahul Chajwa. stated in a statement.
The research team used gravity machine results and ecological and physiological observations to developed a mathematical framework It may apply to all plankton in the ocean. The researchers hope to use biochemistry to further unravel the hidden mysteries of the large number of ipanctons, which can move up and down the water column by regulating their density.
