“Freshwater Hydroid” (Cordylophora caspia)
…a ‘unique' species of Oceaniid hydrozoan which is native to Northern Europe, but has been introduced into the United States and Canada. True to its common name Cordylophora caspia inhabits freshwater and brackish (or sightly salty) habitats, with colonies growing on a myriad of hard surfaces like rocks, pilings, and even mussel shells. Like marine hydroids C. caspia is predatory and will consume a variety of freshwater invertebrates.
Cordylophora caspia populations may benefit from the expansion of zebra and quagga mussels in North America, as they provide substrate. It is thought that the increase salinity in systems impacted by road salt benefit them as well.
Image: Nadine Rorem