How Deep-Sea Isopods Survive Five Years Without Food

Chinese scientists have uncovered the biological mechanism that allows deep-sea isopods to survive without food for more than five years — the longest known fasting record in the animal kingdom. The research, published in the journal Cell on June 5, reveals a dual survival strategy combining an oversized stomach with an ultra-low metabolic rate, regulated by a gene hijacked from bacteria through horizontal gene transfer.

According to Xinhua News Agency, researchers from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS), the Chinese University of Hong Kong, and Northwestern Polytechnical University solved the long-standing “energy paradox” of how these giant crustaceans thrive in the nutrient-poor depths of the ocean.

The Energy Paradox of Deep-Sea Gigantism

Deep-sea isopods, belonging to the genus Bathynomus, are a classic example of deep-sea gigantism — a phenomenon where organisms grow far larger than their shallow-water relatives. While typical isopods measure up to five centimeters, giant isopods can exceed 30 centimeters in length. Yet they inhabit an environment characterized by near-freezing temperatures, crushing pressure, and extreme food scarcity.

This creates a fundamental paradox: larger bodies require more energy, but the deep sea provides very little food. As the Chinese Academy of Sciences explained in its official release, researchers have now revealed how these organisms resolve this contradiction.

A Dual Survival Strategy: Storage and Conservation

The research team discovered that deep-sea isopods employ a two-pronged approach the scientists describe as “increasing revenue and reducing expenditure.” First, the isopod’s stomach occupies approximately two-thirds of its entire body volume — far larger than that of its shallow-water relatives — enabling it to store massive quantities of food when opportunities arise. When fully filled, the stomach contains a finely ground mixture with a high proportion of Chlamydiae bacteria associated with lipid storage, effectively turning the stomach into a slow-release energy reservoir.

Second, the isopod maintains an extremely low basal metabolic rate (BMR) that slows energy consumption, allowing food reserves to be digested and utilized over extended periods. “This phenomenon perfectly explains why deep-sea isopods, in the perpetually cold deep sea, can maintain both a huge body size and extremely low energy consumption,” said LI Fuhua, a researcher at IOCAS, as reported by ScienceNet.

The ND1 Gene: A Bacterial Gift

At the molecular level, the key to this remarkable adaptation is a gene called ND1 — but this gene did not originate in the isopod itself. Through horizontal gene transfer (HGT), a process where genetic material moves between organisms outside of parent-to-offspring inheritance, the isopod acquired ND1 from a symbiotic bacterium. This gene, homologous to a component of Complex I in the electron transport chain, acts as a master regulator of energy metabolism.

What makes ND1 particularly fascinating is its temperature-sensitive behavior. At normal temperatures, introducing ND1 into zebrafish actually accelerated their metabolism, making them less tolerant of starvation. However, under low-temperature conditions simulating the deep-sea environment, ND1 suppressed metabolism and reduced mitochondrial activity, increasing starvation tolerance in zebrafish by 37 percent. Similar effects were confirmed in nematodes and human cell lines.

“Behind the extremely low basal metabolic rate is a set of molecular mechanisms supported by the exogenously acquired energy metabolism gene ND1,” said YUAN Jianbo, first author of the study and researcher at IOCAS.

Epigenetic Optimization

The research also revealed that the ultra-high expression of ND1 is specifically regulated by histone acetylation — an epigenetic modification that controls gene activity without altering the DNA sequence itself. This adds another layer of sophistication to the adaptation, allowing the isopod to fine-tune its energy metabolism with precision.

“This study reveals for the first time the evolutionary strategy of deep-sea organisms regulating energy metabolism through ‘horizontal gene transfer + epigenetic optimization,’” YUAN Jianbo told Xinhua.

Implications for Human Health

Beyond its significance for deep-sea biology, the discovery has potential implications for human health. CCTV News reported that the findings may provide new insights for longevity extension and obesity intervention research. Understanding how ND1 regulates energy allocation and metabolic rate could inform new approaches to treating metabolic disorders.

Broader Scientific Significance

This discovery adds to China’s growing portfolio of high-impact deep-sea research, following significant investments in marine science infrastructure. The collaboration between mainland Chinese institutions and the Chinese University of Hong Kong also highlights cross-regional scientific cooperation.

“Our work not only deciphers the mystery of ultra-long starvation tolerance in deep-sea isopods,” YUAN Jianbo said in the CAS release, “but also provides an important paradigm for understanding how life balances growth and survival in extreme environments.”

What’s Next

The discovery raises several compelling questions for future research. Scientists are now investigating how widespread horizontal gene transfer from bacteria is among deep-sea organisms, whether the ND1 mechanism can be translated into therapeutic applications for humans, and what other genetic adaptations deep-sea isopods may possess. The answers could reshape our understanding of life’s adaptability in Earth’s most extreme environments.