About the Data
Species records include data on invasions history, distribution, ecology, impact, and more. These data were gathered from published literature and targeted surveys. All records have undergone expert review, unless otherwise noted.
Species Profiles
NEMESIS includes detailed information on about 500 species of marine and estuarine of invertebrates and algae introduced to the United States. Each record contains information on taxonomy, distribution, ecology, and impacts, as well as references.
Craspedacusta sowerbii
Craspedacusta sowerbii is a freshwater hydrozoan with a conspicuous medusa stage. It is believed to be native to the Yangtze Valley, China, but the medusa was first described from a water-lily tank in Regent's Park, London in 1880. Since then, it has been introduced to every continent except Antarctica, presumably with shipments of aquatic plants. In North America, it was first recorded in 1885 in Pennsylvania, but has since been reported from 150+ localities, with more occurrences in the east (New Brunswick, Quebec, and Ontario to Florida) than in the west. It occurs frequently in aquaria, but also in artificial and natural ponds, reservoirs, backwaters and pools of rivers. The hydroids grow on rocks, sticks and vegetation. There are no reported ecological and economic impacts of C. sowerbii.
Daily Invader for 2026-05-18