A pill bug that lives under a garden pot curls its body into a small armored ball for self-defense. Far below the ocean’s surface, some of their larger relatives face a tougher problem: how to survive when the next meal doesn’t come for years.
These creatures are called deep-sea isopods, a group of crustaceans with flat, segmented bodies that, new research reveals, have solved the dilemma through a multifaceted biological fix. The world they live in is a cold, dark desert beneath the ocean’s surface, where food only falls in rare “snowflakes” of dead organic matter from above, according to crustacean biologist Jianhai Xiang of the Institute of Oceanography, part of the Chinese Academy of Sciences, and one of the authors of the study published in the journal Cell. “It is a world of perpetual night and overwhelming pressure, yet life finds a way,” Xiang said.
Thanks to their unique biology, these creatures can survive for more than five years without food. New research suggests that their solution is partly anatomical and partly genetic – a huge stomach and a very low metabolism complemented by the action of a gene that helps control bodily energy production. These bottom-dwelling creatures with 14 jointed legs and a hard exoskeleton thrive in the Atlantic, Pacific, and Indian oceans. Some are more than half a meter (20 inches) long. Like pill bugs, they can also curl up into a ball for protection.
The new findings focus on two species: Bathynomus doederleini, a giant isopod found about 300 meters (985 feet) below the sea surface, and Bathynomus jamesi, a giant isopod found about 900 meters (2,950 feet) below the surface. “Deep-sea isopods have a smart survival strategy of ‘earn more, spend less,'” said Jianbo Yuan, a professor at the Institute of Oceanography and lead author of the study.
In deeper-dwelling species, the stomach occupies about two-thirds of the body cavity, allowing the animal to store a large meal when food appears. Yuan compared it to a “nutrient depot” that slowly releases energy while the body works in “standby mode.” With a significantly lower metabolic rate, slower digestion and more efficient use of nutrients, “they can make that one meal last for years,” Yuan said.
Stomach microbes may also help isopods. In species that live at greater depths, bacteria called Chlamydiae — which are often known to cause disease in humans and other animals — have been linked to storing fat, which may give the isopod slow-release energy and the bacteria a stable habitat. “This is a win-win,” Yuan said.
Energy control in isopods may also depend on ND1, a gene that appears to have once belonged to symbiotic bacteria that lived inside the bodies of these animals before it became part of their genome. This process, known as horizontal gene transfer, means that DNA is passed between distantly related organisms rather than from parent to offspring. The isopod appears to have “borrowed” or “hijacked” a bacterial gene that helps control energy production, Yuan said.
“This is surprising because bacteria and animals are completely different, and such transmissions are extremely rare,” Yuan added. “The gene gives the isopod an additional tool to adjust its energy use, especially when it needs to slow down.” Since deep-sea isopods are difficult to study alive, the team tested ND1 in the laboratory on zebrafish, nematodes, and human cells. This gene increases metabolism at normal temperatures, but under cold conditions it helps conserve energy and prolong survival from starvation.
ND1 acts as a metabolic switch, speeding up or slowing down energy use depending on the environment, Yuan said. Horizontal gene transfer could give organisms a faster route to acquiring new traits than normal inheritance alone, helping some organisms compete with others in extreme environments, said study co-author Kaho Chu, professor emeritus at the Chinese University of Hong Kong.
The deep sea is “the largest living space on Earth,” and the extraordinary evolutionary adaptations of its inhabitants could offer ideas for medicine, robotics and environmental conservation, Xiang said. Understanding how animals survive extreme food scarcity also helps researchers think about resilience in a changing planet, including food web disruptions and climate change, Xiang said.
(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)
