New nudibranch species discovered in deep ocean darkness
Scientists from the Monterey Bay Aquarium Research Institute (MBARI) have discovered a new species of nudibranch. They encountered it in the depths of the Pacific Ocean, in a location where nudibranchs had not been observed before. However, that was not the most surprising aspect.
Most nudibranchs, colourful and decorative sea slugs, live in shallow bottom waters, often among coral reefs. However, Bathydevius caudactylus surprised scientists with its habitat. Specimens of this species were found in open waters at a depth of over 2,200 metres, where complete darkness prevails.
Most nudibranchs live on the bottom in shallow water, so it was very surprising to find a nudibranch so deep in the water column and far from the bottom,” said Bruce Robison, a marine scientist from MBARI, in an interview with "ScienceAlert."
Scientists observed a total of 157 specimens of this species during dives conducted between 2000–2021. Out of these, 32 were thoroughly examined, and 18 were collected for further laboratory analyses. Genetic studies allowed for the classification of Bathydevius caudactylus as a nudibranch, but it was so distinct that creating a new family was necessary – Bathydeviidae.
An extraordinary species of nudibranch discovered
Bathydevius caudactylus stands out not only for its habitat but also for its unique features. It has a wide, open hood that captures prey, primarily crustaceans. Pink internal organs can be seen through the ethereal, transparent skin on its body.
Moreover, this species exhibits bioluminescence. Scientists observed that when threatened, Bathydevius caudactylus emitted a luminous glow and even shed glowing tail appendages to confuse predators. Studies also revealed that Bathydevius caudactylus is hermaphroditic.
The most exciting aspect of this discovery is that we were able to make the most comprehensive initial description of a new deep-sea species ever presented (anatomy, respiration, bioluminescence, reproduction, feeding, genetics, behaviour),” Robison told the ScienceAlert portal.
The results of these extensive studies, published in the journal "Deep-Sea Research Part I," indicate that the evolution of nudibranchs is much more flexible than previously thought. "Bathydevius is radically different from all other nudibranchs because it is well adapted to live in a very different habitat; evolution has overcome the challenges of survival where it lives, and it is very well-suited to succeed there,” summed up Robison.
