The stealthy predator Mnemiopsis leidyi, also known as the sea walnut, uses tiny hairs, called cilia, to create a current which prey don’t notice until they are sucked into its mouth region, surrounded by two large oral lobes. The sea walnut swims using fused cilia, which diffract light in many colors in this photo.

Mnemiopsis leidyi, as it’s formally called, is a ctenophore, a group of simple animals often described as jellyfish that propel themselves using tiny hairs, called cilia.

These jellyfish are native to the Atlantic Coast of the Americas, but they can be successful, even devastating, when introduced elsewhere. In the 1980s they showed up in the Black Sea, most likely transported by ships, and multiplied. Within a few years, the Black Sea’s anchovy fishery collapsed. Mnemiopsis was one of the culprits, since it both competes with the filter-feeding fish for food and also consumes anchovy eggs and larvae.

Mnemiopsis has also established itself elsewhere, including the eastern Mediterranean, the Caspian Sea, the Adriatic Sea, the Baltic Sea, parts of the North Sea, and elsewhere, according to the scientists.