‘Gatling Gun’ Plankton Reveals Violent Microbial World

New research gives us the first hi-res videos of a bizarre, microscopic arms race.

Is the bizarre blob in this video animal, vegetable, or mineral?

Actually, it's none of the above—these single-celled organisms are dinoflagellates, a type of protist that seems to bear more resemblance to aliens than to Earthly life forms.

“Looking at these cells under the microscope...they're like spaceships scudding around with armor-plated exteriors,” says Greg Gavelis, a biologist who researched these creatures while at the University of British Columbia. “They'll bump into each other, shoot little volleys of missiles at each other.”

WATCH PLANKTON "HARPOON" THEIR PREY

In fact, these oceanic plankton are engaged in a heated arms race. Gavelis and his colleagues recently published a paper describing the especially warlike adaptations of two particular genera of dinoflagellates, Polykrikos and Nematodinium.

Through painstaking work—the researchers had to collect cell samples in the wild, only about one in three of which was usable—Gavelis and his fellow researchers were able to build the first 3D models of the ballistic mechanisms these general use to attack other dinoflagellates.

Polykrikos cells have a capsule, called a nematocyst, that contracts to propel a sharp stylet through the water—and through the armour of another microbe. A tubule connected to the stylet acts as a tow line, which the predatory cell uses to draw the prey cell close enough to strike—at which point the predatory cell actually unzips its own cell membrane to engulf the prey cell.

Nematodinium has a very similar nematocyst. Or rather, it has 11 to 15 nematocysts arranged in a ring that all launch simultaneously, earning it the “Gatling gun” nickname.

“The Gatling gun kind of seems like overkill,” admits Gavelis. “But if you really want to eat dinoflagellates, you’ve got to bring some weapons to the fight” to overcome the hard silica armour, toxic spikes, and various projectiles these organisms use to defend themselves.

All of this cellular conflict happens on an incredibly microscopic scale: to put it in perspective, the average human being is to a blue whale what a dinoflagellate cell is to a millimetre. (Learn why microbes hold the key to life on earth.)

THE CRAZY LIVES OF HYDROTHERMAL VENTS

LIFE AQUATIC Tubeworms (red), an eelpout fish, and a crab jockey for space near a hydrothermal vent on the mid-Atlantic Ridge. (Learn about the weird animal community at the Pacific Ocean's deepest hydrothermal vent.)
PHOTOGRAPH BY EMORY KRISTOF, NATIONAL GEOGRAPHIC CREATIVE

TINY BUBBLES Carbon dioxide bubbles out of the seafloor at the Champagne Vent in the Western Pacific Ocean. The wide range of chemicals that bubble out of hydrothermal vents fuel microbes that form the base of ecosystems unlike those anywhere else.
PHOTOGRAPH BY PACIFIC RING OF FIRE 2004 EXPEDITION. NOAA OFFICE OF OCEAN EXPLORATION; DR. BOB EMBLEY, NOAA PMEL, CHIEF SCIENTIST

OVERLAP Microbial mats coat a coral reef in a bizarre overlap of habitats 190 metres down in the Western Pacific Ocean. Chemicals released by a hydrothermal vent power the microbes, while sunlight provides energy for the reef.
PHOTOGRAPH BY PACIFIC RING OF FIRE 2004 EXPEDITION. NOAA OFFICE OF OCEAN EXPLORATION; DR. BOB EMBLEY, NOAA PMEL, CHIEF SCIENTIST

SMOKERS Superheated water laden with metals like iron, copper, and zinc sulphide builds up towering chimneys in an image taken in the Western Pacific Ocean's Mariana Arc region. These towers are about 9 metres tall.
PHOTOGRAPH BY PACIFIC RING OF FIRE 2004 EXPEDITION. NOAA OFFICE OF OCEAN EXPLORATION; DR. BOB EMBLEY, NOAA PMEL, CHIEF SCIENTIST

RING OF FIRE White water, which looks like smoke, spews out of small sulphur chimneys in the Western Pacific Ocean. The area was named the Champagne Vent because carbon dioxide bubbles fizz out of the seafloor.
PHOTOGRAPH BY PACIFIC RING OF FIRE 2004 EXPEDITION. NOAA OFFICE OF OCEAN EXPLORATION; DR. BOB EMBLEY, NOAA PMEL, CHIEF SCIENTIST

Researchers initially thought these nematocysts might be genetically similar to those of cnidarians, animals such as jellyfish and sea anemones. Even though cnidarians’ and dinoflagellates’ most recent common ancestor lived over a billion years ago, putting them about as far apart on the evolutionary tree as it’s possible to go, they are the only organisms found to use nematocysts. (Watch this octopus eat a jellyfish, then use it as a weapon.)

However, to their surprise, the researchers found that the similar nematocysts are an example of convergent evolution, rather than a shared genetic trait. In fact, the plankton’s ballistic mechanisms are actually much more complex than those of cnidarians.

Dinoflagellates’ incredible diversity of traits and behaviours is what makes them so worthwhile to research. “Any rule that you come up with in biology, there's some sort of exception that you'll find in dinoflagellates,” says Brian Leander, a zoologist and the senior author of the study. More species of “dinos” are being discovered every month.

Even aside from the joy of discovery Leander describes as an “adrenaline rush,” microbial research can have outsized impacts. Polykrikos are now understood to predate several kinds of microbes responsible for toxic algal blooms. And pioneering medical applications show that planktonic compounds can be used as a chemotherapeutic against melanoma, or even as microscopic syringes that deliver drugs directly to a patient's cells.

For Leander, a teacher, it’s all about the human angle. “That's a huge reward—the exploration of this biodiversity through the eyes of people who are just starting out in their careers in science,” he says. “I absolutely love it.”

 

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