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Blackfordia virginica
Image courtesy of Mariah Meek, University of California Davis. Image of immature medusae (top) and polyps (bottom)
Blackfordia virginica
Taxonomic Group: Cnidarians-Hydrozoans


Blackfordia virginica is a hydroid with a conspicuous planktonic medusa stage and a small obscure hydroid stage. It was first described from Norfolk Harbor and Hampton Roads, Virginia in 1904. There is some disagreement as to where this species is native, but based on previous evidence we are treating this species as having a Black Sea origin. It has been introduced to Europe, the Caspian Sea, South Africa, Mexico, South America, China, India and the east and west coasts of the United States. Polyps of B. virginica have only been reported from estuarine habitats, but medusae have been found in open waters. The polyps grow on aquatic vegetation and the undersides of hard substrates. The medusa stage of this species has the potential to alter planktonic food webs through predation on zooplankton; however, the extent of its impacts have not been determined.

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Fofonoff PW, Ruiz GM, Steves B, Simkanin C, & Carlton JT (2018)
National Exotic Marine and Estuarine Species Information System.
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Marine Invasions Lab
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