Unknown species discovered during deep-sea expedition

Transparent sea cucumbers, bowl-shaped sponges and pink sea pigs are some of the fascinating animals discovered during a deep-sea expedition to the Pacific Ocean.

In March, a 45-day research expedition to the Clarion Clipperton Zone between Mexico and Hawaii in the eastern Pacific Ocean came to an end. One of the scientists on board the British research vessel James Cook was Thomas Dahlgren, a marine ecologist from the University of Gothenburg and the NORCE research institute.

“These areas are the least explored on Earth. It is estimated that only one in 10 animal species living here have been described by science,” he says.

Image of a transparent sea cucumber.

This transparent sea cucumber belongs to the Elpidiidae family and is called ‘unicummber’. You can clearly see his intestines and that he has eaten sediment. We can only guess what the long tail is for, but probably for swimming.


The area studied is part of the Abyssal Plains, deep-sea areas at a depth of 3,500 to 5,500 meters. Although they cover more than half of the Earth’s surface, very little is known about their fascinating animal life.

“This is one of the few cases where researchers can be involved in discovering new species and ecosystems in the same way as in the 18th century. It is very exciting,” says Thomas Dahlgren.

Sea cucumbers and glass sponges

The animals that live in these deep-sea areas have adapted to a life with very little nutrition. Most feed on organic debris, known as marine snow, that falls from the more productive area close to the surface. As a result, this animal population is dominated by filter feeders, such as sponges, and sediment feeders, such as sea cucumbers.

“The lack of food causes individuals to live far apart, but the species diversity in the area is surprisingly high. We see a lot of exciting specialized adaptations in the animals in these areas,” says Dahlgren.

Using a remotely operated vehicle (ROV), the research team photographed life in the deep sea and took samples for future research. One of the species caught on camera was a bowl-shaped glass sponge, an animal believed to have the longest lifespan of any creature on Earth. They can live up to 15,000 years.

Image of a pink sea cucumber

One of the species discovered during the expedition was the pink sea pig, or ‘Barbie Sea Pig’ as it is known in English. It got its name because of its pink color and small feet.


Another species discovered during the expedition was a pink sea pig, a sea cucumber of the genus Amperima. The species moves very slowly with its tube feet over the desolate plains in search of nutrient-rich sediments. The growths on the front of the underside are new feet that are used to put food in the mouth.

“These sea cucumbers were among the largest animals found on this expedition. They act as vacuum cleaners on the ocean floor and specialize in finding sediment that has passed through as few stomachs as possible,” says Dahlgren.

Threatened by mining

The aim of the expedition was to map the biodiversity of the area, where deep-sea mining of rare metals used in solar panels, electric car batteries and other green technologies is planned. Several countries and companies are waiting for permission to mine these metals bound to mineral nodules lying on the ocean floor. The scientists want to know more about how mining can affect the ecosystem, record existing species and discover how the ecosystem is organized.

“We need to know more about this environment to protect the species that live here. Today, 30% of these marine areas in question are protected, and we need to know whether this is enough to ensure that these species are not endangered. risk of extinction,” says Dahlgren.

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