New findings about sea squirts reveal details about invasive abilities

For a tiny creature with such a cute and seemingly harmless name, the sea squirt has done a lot of damage in a relatively short time.

Now thanks to modern genetic analysis techniques, a trio of researchers from the university’s Great Lakes Institute for Environmental Research have identified three previously unidentified sub-types of sea squirts, commonly known as the golden star ascidian, and discovered new clues about their capacity – and possibly the capacity of other organisms – for invading various ecosystems.

Sea squirt colony

A sea squirt colony.

Known by its scientific name as Botryllus schlosseri, the ascidian is a small, saclike underwater creature that forms dense colonies that attach themselves to rocks or other hard surfaces on the shallow zones of ocean floors. An invasive species likely brought to North America via European shipping during the early 19th century, they eat tiny organisms by filtering water through their systems. When large numbers of them get together, they can take over ecosystems and choke out other species by competing for the same sources of food.

Under the direction of GLIER researchers Melania Cristescu and Hugh MacIsaac, former master’s student Dan Bock studied genetic data from golden star ascidians found along the southern and northern coasts of Europe and the eastern and western coasts of North America. Of the species they identified, one in particular was especially widespread across all regions, leading the researchers to believe that it’s especially adept at invading new ecosystems.

“Their invasive ability can evolve a lot more quickly than we originally thought,” said Bock, who is first author on a paper on the subject that was recently published in the academic journal Proceedings of The Royal Society B. “They can evolve traits that can help them adapt to new environments more quickly than we thought.”

Bock, currently working on a PhD at the University of British Columbia, said a fundamental goal of studying ecology is to determine how species spread, but very little is known about the attributes that allow species to expand their ranges and become widespread during the historical evolution of groups of organisms. Because it’s a model organism, the researchers believe the way the sea squirt has spread and evolved may provide important insights about how other invasive species my do the same.

Ultimately the work is important for identifying potential new invaders and protecting ecosystems before they become overtaken by new species introductions, said Dr. Cristescu.

“It can take hundreds of generations for ecosystems to rebalance themselves,” she said.

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