Dragons, sea toads and the longest creature ever seen found on undersea peaks off South America

<span>An octopus on an unexplored seamount east of Motu Motiro Hiva, an uninhabited island along the Salas y Gómez ridge</span><span>Photograph: ROV SuBastian/Schmidt Ocean Institute</span>
An octopus on an unexplored seamount east of Motu Motiro Hiva, an uninhabited island along the Salas y Gómez ridgePhotograph: ROV SuBastian/Schmidt Ocean Institute

Squat lobsters, bright red sea toads and deep-sea dragon fish were among more than 160 species never previously seen in the region that were spotted on a recent expedition exploring an underwater mountain range off the coast of South America. Researchers from the California-based Schmidt Ocean Institute believe that at least 50 of those species are likely to be new to science.

  • A Chaunax (member of the sea toad family) found to the south of Rapa Nui, near the western end of the Salas y Gómez ridge

Underwater mountain ranges are oases of life and biodiversity, where communities of different organisms band together: some creatures make the most of the elevation and unique currents that the peaks provide, while others find refuge in the nooks and crannies of the rocky slopes to build intricate structures.

Erin Easton, of the University of Texas Rio Grande Valley, was the chief scientist on the 40-day research voyage along the Salas y Gómez ridge, which spans the waters from Chile to Rapa Nui, also known as Easter Island. “We’re still astounded by what we observed,” she says.

  • Soldierfish gather near the summit of an underwater seamount

  • Top left: A Coronaster starfish recorded on the south-western flank of Rapa Nui; right: a deep-sea dragon fish, an apex predator with large jaws and fang-like teeth, seen off the Salas y Gómez ridge; above: a Diadema sea urchin spotted north of Motu Motiro Hiva, an uninhabited island along the Salas y Gómez ridge

As Easton’s research team collected data on 10 peaks along the 2,900km range of 110 seamounts, they spotted unique communities on each one. Species included sea toads among the various fish, crustaceans such as pale squat lobsters, molluscs, “gardens” of glass sponges, deep-water coral reefs, galaxy siphonophores – giant thread-like creatures that use bioluminescence to hunt and may be the longest animal ever recorded.

  • A galaxy siphonophore north of Motu Motiro Hiva island

As these seamounts sit in an area of ocean where the water is so clear that the sun’s beams penetrate further into the water than anywhere else in the world, the scientists also found some of the deepest-known organisms that depend on photosynthesis.

They found a species of photosynthetic wrinkle coral (Leptoseris) 197 metres below the surface – 25 metres deeper than previously recorded – as well as crustose coralline algae at 350 metres.

  • Top: The deepest-known photosynthesis-dependent wrinkle coral (Leptoseris) recorded to the north of Motu Motiro Hiva; bottom left, a hydroid seen on the northern side of Rapa Nui; right, Chrysogorgia coral and a squat lobster on the northern edge of Motu Motiro Hiva

“Pinks and magentas and light greens and dark green – and then you start seeing some oranges mixed in there too. It’s beautiful,” says Easton.

“It’s like you are driving a car down a dark road at night with the headlights on and all you can see is what is in front of you. The fact that we discovered so much, without even looking off to the side, [means] we clearly are missing so much more.”

  • A squat lobster among primnoid coral partially overgrown with two species of zoanthid coral east of Motu Motiro Hiva