It’s International Polychaete Day, and this dazzling deep-sea worm is the star of the celebration!

The golden sea mouse, Laetmonice, wears a coat of brilliant bristles. That flashy ‘fit has a purpose: protection from hungry predators. For most scale worms, those bristles, called chaetae, help with locomotion. But Laetmonice has specialized harpoon chaetae that are ornamented with fang-like projections, spines, or other hooked structures that make an unpleasant mouthful for predators.

We’ve seen the golden sea mouse with our remotely operated vehicles (ROVs) at depths ranging from 1,500 to 4,000 meters (4,900 to 13,100 feet). They’re especially common on the muddy seafloor at Station M, an MBARI research site off Central California. Laetmonice is a deadly beauty—they scurry along the seafloor searching for prey including other worms, crustaceans, and echinoderms like sea stars and urchins. They’ll even eat decaying material and dead animals they find in their hunt.

Laetmonice belongs to the family Aphroditidae. Nicknamed the “sea mice,” these scale worms are remarkably diverse and can be found in virtually every marine environment, from shallow sunlit seas to the inky depths of the midnight zone. To date, scientists have identified around 174 different species of sea mice across seven genera.

In some of these clips, you’ll see two red dots. Those are lasers mounted on the ROV to measure the size of animals and other objects of interest. The distance between the dots is 29 centimeters (11 inches).

Learn more about scale worms:    • The ocean is bristling with scale worms  

Video editor: Kyra Schlining
Science advisor: Karen Osborn
Music: Laetmonice by Catechism (https://cccatechism.bandcamp.com/)