Scientifically Speaking: The animal that can survive five years without eating

What if I told you there is an animal nearly the length of your forearm, living on the deep ocean floor, that can get by for five years without a single meal? Deep-sea isopods live on the seafloor across the Atlantic, Pacific, and Indian oceans. (Reuters file)

I read a lot of scientific papers looking for topics for this column. Sometimes, even as a biologist, I come across a description of a form of life that amazes me. A new paper in Cell, from Jianbo Yuan and colleagues at the Institute of Oceanology of the Chinese Academy of Sciences tells us more about a deep-sea isopod, a scavenging crustacean with a flattened, segmented body, fourteen jointed legs, and a hard outer shell that can survive years without eating.

How do these animals achieve this feat? It turns out there is no single trick. The animal survives through a whole set of features that together suit it to one of the harshest environments on Earth.

Deep-sea isopods live on the seafloor across the Atlantic, Pacific, and Indian oceans. Their world is vast, dark, cold, and almost entirely without reliable meals.

The deep sea is the planet’s largest living space and one of its least forgiving. At these depths, sunlight no longer helps microbes make food. Food is scarce and unpredictable, most of it sifting down as marine snow, the slow drift of dead plankton and other organic matter falling through dark water. Now and then something larger lands such as a dead fish or a whale carcass, and for a while the seafloor feasts. Then the famine returns.

Also Read: Scientifically Speaking: Plastics are inside us, but we can reduce exposure

The researchers compared two species of isopods, living at two different depths. The deeper-dwelling animal has an enormous stomach, swollen until it fills roughly two-thirds of the body. When the rare chance to eat arrives, it gorges, filling that stomach in preparation for a long wait. Cut one open after a meal and you find a dense, almost fully digested paste with the consistency of mud.

Bodies often differ between species in ways that match their habitats. But there are other more remarkable findings in the recent paper.

The deep-sea isopod also lowers its metabolism dramatically, running its body on standby mode. Researchers found a group of bacteria called Chlamydiae, better known for causing disease, linked to fat storage. The bacteria may help the animal bank energy for slow use.

Strangest of all is a gene called ND1, which looks out of place in the isopod’s genome. It appears to have come from bacteria. The researchers argue that an ancestral isopod picked it up from a microbial source roughly 16 million years ago.

Step back and think about this for a moment. Inheriting genes from parents is ordinary. Animals borrowing genes from wildly unrelated microbes is incredibly rare. In fact, it was unheard of until a few decades ago.

This begs the question: what is a microbial gene doing inside a deep-sea animal?

Also Read:Scientifically Speaking: Microplastics are inside us, but we can reduce exposure

Well, it appears that inside the isopod, ND1 helps tune how the animal spends energy. To test this, researchers genetically inserted the gene into other animals, including fish, to watch it work. At ordinary temperatures, the gene sped metabolism up and left the fish less able to withstand starvation. But under cold conditions meant to mimic the deep sea, it reversed course, extending starvation survival by 37 percent.

We scan distant planets for alien life, but on our own planet our own oceans hold weird and wonderful creatures most of us will never see.

Imagine this then. Somewhere on the dark seafloor, an armored scavenger lies dormant waiting for a meal that may not come in years. It will not die of starvation, because its biology makes it suited for that wait.

Anirban Mahapatra is a scientist and author. His most recent book is When the Drugs Don’t Work. The views expressed are personal