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Why a newly spotted 'huge' invasive slug could pose problems for Long Island Sound

The Doris pseudoargus, a yellow European nudibranch that feeds entirely on sponges was found on a lost lobster trap recovery trip in Long Island sound off the coast of Groton, Connecticut.
The Maritime Aquarium
The Doris pseudoargus, a yellow European nudibranch that feeds entirely on sponges was found on a lost lobster trap recovery trip in Long Island sound off the coast of Groton, Connecticut.

Rebha Raviraj was recently on a boat off the coast of Groton, Connecticut, helping to retrieve abandoned lobster traps, when she saw a “huge, bright yellow” sea slug attached to a cage.

The conspicuous critter dwarfed slugs native to Long Island Sound, which can be smaller than the tip of your finger. This slug was 1.5 inches long.

“I immediately knew that was worth collecting to bring back onto land for a closer look,” Raviraj said.

Raviraj, a 23-year-old conservation research assistant at The Maritime Aquarium in Norwalk, eventually identified the sea slug as Doris pseudoargus, a large and invasive sea slug normally seen in European waters.

It’s the first time the European slug has been found in Long Island Sound.

The Doris pseudoargus, a yellow European nudibranch that feeds entirely on sponges was found in Long Island sound off the coast of Groton, Connecticut.
The Maritime Aquarium
The Doris pseudoargus, a yellow European nudibranch that feeds entirely on sponges was found on a lost lobster trap recovery trip in Long Island sound off the coast of Groton, Connecticut.

The sighting off the Connecticut coast was a first. But the sea slug (scientists call it a “nudibranch”), has been making headway in New England waters.

Since 2017, it’s been found off the coast of Cape Ann, Massachusetts.

Scientists at the Maritime Aquarium are now studying the invasive slug, which feeds on sponges, to gauge any potential future impacts on Long Island Sound’s ecosystem.

“We’re gathering up different sponge species that are native to Long Island Sound, to see which sponges it's more attracted to, which ones it is eating more,” Raviraj said.

If native sponges are a favorite food of the invasive sea slug, Raviraj said, that could harm the Sound’s water quality.

“Sponges are filter feeders,” she said. “And they do a great job of filtering our water.”

Sponges can also provide shelter and habitat for other sea creatures.

Why and how the slug migrated to the Sound remains unclear. But Raviraj said sea slugs are sensitive to changes in water temperature and climate change is suspected.

Jennifer Ahrens is a producer for Morning Edition. She spent 20+ years producing TV shows for CNN and ESPN. She joined Connecticut Public Media because it lets her report on her two passions, nature and animals.