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Comb Jellies: The Extraordinary Creatures That Can Fuse, Reverse Aging, and More

Comb jellies of the Phylum Ctenophora. (Photo: © Smitty411| Dreamstime.com)

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By Josh Longster

November 19, 2024
3:54 pm
Los Angeles, CA

In the world of marine biology, the comb jelly, a translucent, gelatinous creature, has long intrigued scientists with its bizarre and remarkable abilities. These animals, part of the phylum Ctenophora, have captivated researchers due to their unusual behaviors, from the ability to fuse with other individuals to their seemingly miraculous capacity to reverse aging under certain conditions. Recent discoveries have shed light on the extraordinary life-cycle flexibility of these creatures, unveiling not only their survival mechanisms but also raising questions about their potential for regenerative medicine. Two Become One One of the comb jellies’ most surprising talents is their capacity to fuse with other jellies, effectively becoming one organism. This phenomenon was first discovered by biologist Kei Jokura and his team. Jokura, who was conducting research on comb jellies,

Two Become One

One of the comb jellies’ most surprising talents is their capacity to fuse with other jellies, effectively becoming one organism. This phenomenon was first discovered by biologist Kei Jokura and his team. Jokura, who was conducting research on comb jellies, initially observed a particularly unusual specimen—a jelly that appeared to have two heads, two mouths, and two anuses. Upon closer inspection, it became evident that two individual comb jellies had fused together, creating a single, functioning organism.

This discovery led the researchers to experiment further, deliberately slicing comb jellies and placing them near one another. To their amazement, the jellies fused almost 90% of the time. The resulting fused creature shared a nervous system and coordinated its movements as one entity. The team’s experiments with feeding also demonstrated the depth of this fusion. When one jelly consumed brine shrimp, the food passed through both jellies’ digestive systems, with one jelly excreting the waste. This cooperation between fused individuals suggests that the creatures are not just physically connected, but neurologically linked as well, behaving as a unified organism despite having started as separate beings.

Turning Back the Clock

While fusion is an incredible survival tactic, comb jellies possess another remarkable skill: the ability to reverse their aging process. Known for their regenerative properties, comb jellies can, under certain conditions of stress, transform from an adult back into a juvenile state—a phenomenon that had previously only been observed in few creatures in the animal kingdom like the “immortal jellyfish” Turritopsis dohrnii. Recent studies have confirmed that the Atlantic comb jelly, Mnemiopsis leidyi, or the sea walnut, can undergo a similar reverse-aging process.

This discovery, made by marine biologists Joan Soto-Angel and Pawel Burkhardt at the University of Bergen, involved exposing adult comb jellies to environmental stressors like starvation and physical injury. Under these conditions, the adult jellies would shrink and revert to a larval form. The researchers found that the jellies not only regressed morphologically but also exhibited feeding behaviors typical of their earlier life stages. This “time-travel-like” metamorphosis allowed the comb jellies to survive by accessing food sources that were unavailable to their adult forms.

This process did not require a complete breakdown of the jelly’s cellular structure, like the one seen in the immortal jellyfish. Instead, the sea walnut maintained its identity and simply reshaped its morphology, shedding its adult characteristics in favor of a more primitive, larval body. The ability to regress in response to stress offers the comb jelly a significant survival advantage, allowing it to adapt to harsh conditions and avoid the dangers of aging and starvation.

Comb Jellies’ Unique Life-Cycle Plasticity

The life-cycle plasticity of comb jellies has deep evolutionary implications. Mnemiopsis leidyi, one of the earliest animal lineages, exhibits this extraordinary capacity for developmental flexibility. Researchers suggest that this ability may have evolved as a survival mechanism in response to fluctuating environmental conditions, offering the comb jelly a means of ensuring its survival when food is scarce or when the species faces other environmental pressures.

Moreover, this ability to reverse aging and fuse with other individuals may explain its invasive success across the world’s waters. Known to invade new ecosystems via ships’ ballast water, this comb jelly has spread across the Black and Caspian Seas, outcompeting native species and disrupting local fisheries. Its resilience, fueled by its regenerative abilities, has allowed it to thrive in a wide range of environments, making it a highly adaptable species.

Implications for Regenerative Medicine

The findings surrounding comb jellies are not just important for understanding marine life—they also hold promise for the future of regenerative medicine. The comb jellies’ capacity to fuse and heal their bodies, as well as to reverse aging, could provide valuable insights into how we might apply similar principles to human health.

Allison Edgar, an integrative biologist at the New Jersey Institute of Technology, has expressed excitement about the potential applications of this research for humans. She notes that if the regenerative abilities of comb jellies could be harnessed, they might one day offer solutions to organ transplants, allowing patients to heal quickly and fully integrate transplanted organs without rejection. The rapid merging of nervous systems in fused comb jellies could also inspire methods for regrowing or reattaching limbs, helping individuals regain full control over transplanted or prosthetic limbs.

While such advances are still a long way off, the ability to regenerate and adapt offers a glimpse into a future where human healing might mirror the biological resilience observed in these fascinating creatures.

The world of comb jellies is one of continuous discovery, and as researchers continue to explore their mysterious biology, the possibilities seem endless.