Scientists uncover new mollusk species co-habiting with an anemone in the North Atlantic abyss

A new species of tusk shell, a burrowing marine mollusk, has been discovered in deep, North Atlantic waters by scientists from the British Antarctic Survey and the Senckenberg Society for Nature Research. The newly discovered mollusk lives in the abyss—below 3,300m—with an anemone on its shell, an arrangement that has not been seen before in this region. The study is published in the journal Marine Biodiversity.

The team collected several specimens of the new tusk shell mollusk with anemones from the seafloor and observed many more using seafloor imaging. The anemone changes the burrowing lifestyle of the mollusk, which is unable to burrow as deep as it could without its passenger.

Lead-author, Katrin Linse, Senior Biodiversity Biologist at BAS, says, “It was exciting to discover a new species, but realizing its living arrangement has not been seen before in the region in such deep waters was truly fascinating! It serves as a reminder that we know so little about life in the deep, particularly the way that it adapts and how species pull together to benefit from each other’s presence.”

Life in the abyss is hard. No sunlight reaches this depth and very few humans have been this deep in special submersibles. To investigate life on the abyssal ocean floor, Katrin Linse and colleagues on board the RV Sonne used a small net, known as an Agassiz trawl which can be deployed thousands of meters deep, to collect samples from the floor of the Labrador Sea between north-eastern Canada and western Greenland.

They collected several specimens of the new mollusk, which at 1.1 cm in diameter and 5.5 cm long is larger than its closest tusk shell relatives. It is slightly curved, with 60 ribs, and a member of the genus Fissidentalium which has over 60 known species. They named it Fissidentalium aurae, after the Latin word for breeze, referring to the windy conditions during the expedition.

Co-author Jenny Neuhaus, Ph.D. student at Senckenberg, sampled DNA from the anemone and checked its genetic barcode against known barcodes in genetic databases, resulting in no close match. The position of the anemone in the tree of life and its scientific name is a riddle still to be solved.

The association between a burrowing tusk shell with an anemone has been previously seen in the deep Pacific Ocean, but never in the Atlantic. The research underlines the benefit of deep-sea imagery to support descriptions of species with information on their habitat and ecology.

“The discovery of this beautiful species shows that the deep sea never ceases to surprise us,” says Neuhaus.

“Not only is it fascinating to scientists to find new species, but also sparks curiosity in the general public. Last week, our research earned a science award sponsored by the maritime city of Wilhelmshaven. We are grateful for this recognition, which emphasizes the importance of collaborative efforts in deep-sea research.”