New deep-sea nudibranch discovery challenges marine norms
Monterey Bay Aquarium Research Institute (MBARI) scientists have discovered a new nudibranch species. They encountered it in the depths of the Pacific Ocean, where nudibranchs had not been found before. However, that was not the most surprising aspect.
Most nudibranchs, colourful and ornate sea slugs, live in shallow waters near the bottom, often among coral reefs. However, Bathydevius caudactylus surprised scientists with its habitat. Specimens of this species were found in open water at depths of over 2,195 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 at MBARI, in an interview with "ScienceAlert".
The scientists observed a total of 157 specimens of this species during dives conducted from 2000 to 2021. Among them, 32 were thoroughly examined, and 18 were collected for further laboratory analysis. Genetic studies allowed for the classification of Bathydevius caudactylus as a nudibranch, but it was so distinct that it necessitated the creation of a new family – Bathydeviidae.
An extraordinary species of nudibranch discovered
Bathydevius caudactylus is distinguished not only by its habitat but also by its unique features. It possesses a broad, open hood with which it catches prey, mainly crustaceans. Through the ethereal, transparent skin on its body, pink internal organs can be seen.
Moreover, this species exhibits bioluminescence. Scientists observed that in the face of danger, Bathydevius caudactylus emitted a luminous glow and even jettisoned glowing tail appendages to confuse predators. Studies also found 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) – said Robison to the portal ScienceAlert.
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 – summarised Robison.
