Discover a new species and locate it on theevolution tree is a great responsibility. I have been fortunate to name four species from some of the deepest, most isolated and least sampled regions of the ocean.
Each new species helps us better understand life in the hadal zone (more than 6,000 meters deep). Please let me introduce you Eurythenes atacamensis.
Eurythenes atacamensis> figure H: female observed at -8,052 meters; figure PJ: juvenile observed at -6,714 meters; figure PM: male observed at -7.204 m © Johanna Weston / Marine Biodiversity
Eurythenes atacamensis is a
amphipod, a type of crustacean close to shrimp, which is endemic to the
Peru-Chile trench (or Atacama pit). With a length of eight centimeters, he is twice the size of his next of kin, which makes him a giant. Juveniles and adults can be found in a large vertical zone that is 4,974 to 8,081 meters deep. This includes the deepest place, known as the Richard’s Deep.
It is one of the most abundant species in the pit with a trio of sea slugs and isopods with long legs that look like spiders. This amphipod
necrophage plays a vital role in the food web by collecting and redistributing food that comes down from above. It quickly detects and consumes dead animals, like the mackerel bait we set in our trap. Unfortunately, he can also accidentally ingest microplastics.
VIDEO : Time-lapse images of Eurythenes atacamensis feasting on the bait placed 6,980 meters deep in the Atacama pit
A habitat full of darkness and extremely low temperatures
Eurythenes atacamensis lives in one of the 35 pits that reach hadal depths. These pits are formed by a geological process called subduction (when a tectonic plate sinks under another plate, causing the ocean floor to sink). The volume of the Atacama Trench is almost the same as that of the nearby Andean Cordillera, which was also created by the tectonic subduction zone.
The Atacama pit, in dark blue, borders the coasts of Peru and Chile © Ouest-France
If we compare it with the conditions at the surface, the hadal environment (or deep water) seems extreme. It is completely dark there and the water temperature varies from 1 ° C to 4 ° C at the deepest points. The hydrostatic pressure there is 600 to 1,100 atmospheres, which is equivalent to placing a ton at your fingertip.
This environment is quite normal for the organisms that live there. The species of the hadal zone have adaptations biochemical, morphological and behavioral that allow them to live in pits. Studying these ecosystems is no easy task. This is why the hadal zone has been little studied compared to shallower places in the ocean.
A fabulous collection of scientific data
In 2018, two international scientific expeditions focused on the southern part of the Atacama Trench. Researchers first set sail on the Chilean ship RV Cabo de Hornos as part of the Atacamex expedition to study the deepest part of the pit, Richard’s Deep. A month later, the German ship
RV Sounds allowed scientists to study a larger portion of the pit ecosystem by taking samples at a depth ranging from 2,500 meters to that of Richard’s Deep.
Unmanned submersibles equipped with robust deep-water imaging equipment and baited traps were used to haul the animals up for closer examination. The two expeditions were a success and made it possible to collect hundreds of hours of images and thousands of amphipods – including Eurythenes atacamensis – and a new species of sea slug, affectionately known as the “little purple lovely” while awaiting an official scientific name.
Scientific illustration of the holotype of Eurythenes atacamensis, a female from a depth of 8,052 meters in the Atacama pit © Johanna Weston / Marine Biodiversity
Once the specimens are brought back to dry land, the meticulous work of sorting, measuring, identifying and describing the new species begins. Eurythenes atacamensis is part of a well-studied genus of the depths (
Eurythene), which is known for what is known as cryptic speciation, that is, it is difficult to visually distinguish one species from another. The superb photos ofEurythenes atacamensis were taken during a
expedition conducted in 2009 in the pit.
At the time, it was considered to beEurythenes gryllus. For new specimens collected in 2018, we took cryptic speciation into account and used an integrative taxonomic approach – which combines traditional morphology (the detailed study of an organism’s shape) with barcodes of an organism. ‘DNA. We then concluded that it was a new, undescribed species.
“Atacamensis” because living in the Atacama pit
Through this taxonomic process, we were able to categorize organisms in order to more easily disseminate biological information. The combination of detailed visual assessment and genetics allowed us to clearly establish thatEurythenes atacamensis was a new species. Once these data seemed reliable to us, we selected several individuals to describe and illustrate them. These are called type specimens – the most important of which is the
holotype or the “name tag” specimen. We chose the term atacamensis in homage to its habitat.
This discovery is a new piece of the puzzle that allows us to know the world in which we live and the subtle interactions between organisms and their environment. It helps us understand how life works in the deepest parts of the ocean, under conditions that seem impossible to land mammals that we are. It also gives us a glimpse of the hadal zone, which is not an extreme habitat devoid of life, but rather a place of extraordinary biodiversity.
This analysis was written by Johanna weston, PhD student in Marine Sciences at the University of Newcastle (England).
The original article was published on the website of The Conversation.
