Marine biologists discover new sea slug species off Pacific coast

California researchers found ‘mystery mollusc’ in deep-sea midnight zone after initially observing it 20 years ago

Researchers in California have discovered a new species of sea slug off the Pacific coast in an area of deep sea known as the midnight zone.

A team with the Monterey Bay Aquarium Research Institute first came across the creature, which they dubbed the “mystery mollusc” in 2000 at 8,576ft (2,613 meters), and spent years documenting the sea slug in order to “prepare the most comprehensive description of a deep-sea animal ever made”.