Native to the Baltic Sea, it invaded the Gulf of Maine in the late 1990s.

[2] It consumes juvenile settling mussels and harpacticoid copepods.

[3] It also engages in a symbiosis with a diatom of the genus Lichmophora,[4] which has also invaded the Gulf of Maine.

[5] It also appears limited to wave-protected habitats, where it prefers filamentous algae.

[5] In 2001, it occurred in densities of up to 19 per square centimeter.