Despite the harsh conditions, strange creatures somehow thrive there. And after decades of struggling to study them, scientists are finally beginning to shed light on the ocean trenches and their inhabitants.
In a new study, scientists from the United States and Chile have uncovered one such species: a swift, ghostly predator from the Atacama Trench off the west coast of South America that stands apart from many other trench dwellers.
Called Dulcibella camanchaca, the creature is an amphipod, a diverse group of shrimp-like crustaceans that typically feed on detritus or forage for food in marine or freshwater habitats. Researchers found four individuals of this species at a depth of 7,902 meters.
According to the authors of the study from the University of Concepción in Chile and the Woods Hole Oceanographic Institution (WHOI) in the US, D. camanchaca is the first large, actively predating amphipod found at such a depth.
Its discovery in the hadal zone (the deepest region of the ocean, located in the ocean trenches) suggests how little we still know about these strange marine underworlds. The trenches may hold biological secrets with valuable applications for humanity, not to mention crucial information about their own ecology and conservation needs.
Studying such extreme habitats on Earth also helps in the search for extraterrestrial life on ocean moons like Europa or Enceladus.
For now, though, the discovery of this unique earthling is big news in itself. The authors note that all other amphipods found in the darkest depths of the Atacama Trench have been ocean scavengers, and while predatory species are known from other trenches, they are still a remarkable discovery anywhere.
Particularly in this case, it seems: D. camanchaca is not only from a previously unknown species, but its morphology and DNA suggest that it is a newly discovered genus.
Two similar amphipod genera are named after characters in a 17th century Spanish novel. "Don Quixote, so the team is continuing this tradition by naming the new genus Dulcibella in honour of the character Dulcinea del Toboso (the scientific nickname Dulcinea is already taken by a beetle).
The species name camanchaca is translated as "darkness" from the languages of indigenous peoples in the near-western part of South America, the researchers note. They chose it to refer to the black depths in which this creature ventures.
"Dulcibella camanchaca is a fast-swimming predator that we named 'darkness' in the languages of the peoples of the Andean region to denote the deep, dark ocean from where it predates," says co-author Johanna Weston, a Hadal ecologist at WHOI.
The white coloration of amphipods is standard attire in dark habitats such as caves or burrows.
The size of this specimen is just under 4 cm, more than twice the size of its closest relatives Dorothea and Cleonardo. Unlike the less mobile amphipods, it moves nimbly in search of food.
D. camanchaca hunts and feeds with the help of specialized raptorial appendages called gnathopods. Foraging opportunities are limited in ocean trenches, but this species appears to feed on other, smaller amphipods.
The Atacama Trench extends 8 km beneath the surface of the eastern Pacific Ocean and is formed as one tectonic plate slowly slides into and beneath another.
Although the trenches are globally classified together as the Hadal Zone, in real life they are physically isolated from each other, like islands of negative space separated by strips of seafloor.
Like islands on the surface, each ocean trench can host its own wealth of endemic species, teeming with creatures found nowhere else. Much more research will be needed to uncover the abundance and diversity of life in the trenches, but such discoveries have much to contribute.
The discovery of a new species is always a major event, especially in such an extreme environment, and the discovery of a genus is even rarer. But what happens in a place like the Atacama Trench adds a unique intrigue, Weston explains, because of what it suggests about other, as yet unknown, inhabitants of this shadowy realm.
"The most exciting thing is that the DNA and morphology data indicate that this species is a new genus, which underscores that the Atacama Trough is an endemic hotspot," she says.
The new species was discovered during a research expedition in 2023, part of Chile's new Integrated Deep Ocean Observing System.
Researchers collected the specimens using a lander or platform that carried scientific equipment (such as baited traps) to the hadala area and back.
"The collaborative effort and integrative approach of this study confirmed that Dulcibella camanchaca is a new species and highlights ongoing biodiversity discoveries in the Atacama Trench. This discovery underscores the importance of continued deep-sea exploration, particularly in the Chilean forecourt. More discoveries are expected as we continue to study the Atacama Trench," says co-author Carolina Gonzalez, an oceanographer at the University of Concepción. | BGNES
