Never say die

Nearly immortal jellyfish could help unlock health secrets

Barcroft Media

Scientists are finding that the world’s oceans are being infested with a specific species of jellyfish—one that can potentially live forever. “We’re facing a worldwide silent invasion,” says Maria Pia Miglietta, a biology researcher at Pennsylvania State University. What makes this particular creature—the Turritopsis dohrnii—so special is its ability to change from its adult state (the tentacle-trailing dome we all know and avoid) back into tiny polyps, restarting what would normally only be a life cycle of a few months and allowing it to create more colonies, and thousands more jellyfish. “It’s like a butterfly,” says Miglietta, “but instead of dying it turns back into a caterpillar.”

The process is called transdifferentiation—that’s when specialized cells change from one type into another. It occurs elsewhere in nature, mostly in partial organ regeneration, but scientists don’t know of any other animals that use it the same way as this particular jellyfish. And learning how the Turritopsis “switches on genes that rejuvenate their cells” may result in major breakthroughs in reversing the cellular degeneration that causes diseases like Alzheimer’s and Parkinson’s, says Stefano Piraino, a professor of biology and environmental science at Italy’s University of Salento. It could also lead to greater insight into the world’s most deadly illness: “I don’t want to say that we will find a solution for cancer,” says Piraino. “But it could contribute to the understanding of how cancer occurs.”

The Turritopsis, which National Geographic has dubbed the “Benjamin Button of the deep,” was first discovered about 130 years ago. It’s only a few millimetres in size, uses tiny stingers to capture, kill and feed on crustacean larvae, and is a favourite meal of sea spiders. The Turritopsis is also quite susceptible to viruses, fungi and bacteria, especially in its polyp stage. Those facts have been known for decades. But the regenerative abilities that set it apart weren’t discovered until 1992. That’s when an Italian student accidentally left an adult specimen in an uncovered bowl of water. He returned to the lab a few days later to find the jellyfish gone and a group of cells in its place. The animal had reverted to an earlier state to survive the stressful conditions in the bowl, something the researchers had never seen before and have so far been unable to study in nature. This finding went relatively unreported until Miglietta published a paper last year, which identified the species’ invasive spread.

Turritopsis has been found all over the world, from Japan to Italy to the United States, and it continues to proliferate. Miglietta believes that cargo ships are carrying the species, causing colonies to pop up whenever ballast water—which ships pump in and out for stability—is dumped in foreign ports. The fact that the jellyfish have also been found nearly 500 km from the entrance of the Panama Canal, far from major shipping routes, is proof that Turritopsis is fully capable of covering large distances on its own. And the jellyfish are adapting to their new environments. In tropical areas, for instance, the species is beginning to shed a few of the tentacles present in its genetically identical relatives living in more temperate places.

But is the jellyfish’s spread an environmental problem? After all, foreign species stowed away in ships have resulted in disastrous consequences in the past. “Some invasions have really nasty, dramatic economic and ecological effects,” says Miglietta. In the 1980s, for instance, a ship dumped ballast water containing another jellyfish, Mnemiopsis leidyi, into the Black Sea. Within a few years the numbers had exploded—the population was estimated to weigh about one billion tonnes, and it completely decimated the fishing industry.

Although worldwide numbers are increasing, experts aren’t predicting a similar catastrophe involving the Turritopsis. This particular jellyfish is usually only found in small colonies, so population concentration remains quite low. Piraino, who was part of the research team that in the early ’90s discovered the species’ ability to restart its life, says that even though Turritopsis is capable of surviving in harsh environments—and has been seen restarting its life cycles up to three times, according to researchers in Japan—it’s simply too small and has too little an impact on ecosystems to be considered a threat. Plus, it appears to be quite tame compared to some of the larger, more virulent species that are carried in ballast water, such as the Mnemiopsis or the Asian clam, a small mollusc that is now clogging underwater intake pipes all over the world. The Turritopsis would only become dangerous, say experts, if the population suddenly exploded.

Piraino says the bigger issue involving the Turritopsis is unravelling its potential medical value. The next step for researchers, he says, is to begin sequencing the Turritopsis’s genome, a process that will likely take a year or two. At that point, scientists will be that much closer to understanding the mechanism that kick-starts transdifferentiation. Then, says Piraino, who knows what the potential might be.

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