The Quiet Web of the Sea: How Delicate Stars Linked the Seafloors of our Planet
Neither do they swim like fish, nor migrate like birds, but the —close relatives of starfish— have achieved around the planet. Invisible to most and forgotten in the depths, they have woven a network of evolutionary connections between oceans. A new study reconstructs their history from DNA and poses a new urgency: .
Fragile stars crossing the oceans without moving
With small bodies, long arms, and a history dating back over 480 million years, brittle stars inhabit the most extreme seabeds. Although they appear immobile, their true ability to move lies in their larvae: . Driven by deep ocean currents, they can travel thousands of kilometers, connecting ecosystems from Iceland to Tasmania without touching land. A team of over 50 researchers analyzed the DNA of 2,600 specimens collected over decades and preserved in 48 museums. The result is an unprecedented genetic map that reveals evolutionary connections between species separated by continents.
DNA in the abyss: a story of silent migration
The genetic analysis showed that species from the North Atlantic share links with those from southern Australia, and populations from New Zealand are related to inhabitants of the Arctic. This astonishing dispersion does not imply uniformity: scientists also detected huge diversity caused by climate changes, geographical barriers, and past extinctions. “The deep sea is not an isolated desert. It is a global highway for biodiversity,” explained Tim O’Hara, lead author of the study and curator at the Museums Victoria Research Institute in Australia. Their work, published in Nature, not only solves an evolutionary puzzle: it redefines our idea of how life is structured in the depths of the planet.
Connected fragility: what is at stake
Brittle stars are not just a scientific curiosity. By connecting abyssal ecosystems, they act as key indicators of environmental health. But that silent network is now threatened. Deep-sea mining, deep-sea trawling, and climate change are eroding habitats that took millennia to form. “Understanding how life moves in these environments allows us to anticipate how to protect it,” says O’Hara. What we once believed to be remote and isolated, we now know is deeply connected. And also, profoundly fragile.
