Cordylophora caspia
Cordylophora caspia
(freshwater hydroid)
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Cordylophora caspia Pallas, 1771

Common name: freshwater hydroid

Taxonomy: available through www.itis.govITIS logo

Identification: This colonial hydroid consists of macroscopic polyps (about 1 mm) connected by a gastrovascular cavity; branching, moss-like in appearance (Pennak1987). Colonies grow up to 5 cm, which varies depending on conditions (Folino 2000).

Size: Colonies to 5 cm, polyps around 1mm.

Native Range: Colonies to 5 cm, polyps around 1mm.

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Nonindigenous Occurrences: San Francisco Bay, California (Mills and Sommer 1995).  Coastal waters of Florida (Carlton and Ruckelshaus 1997).  Illinois River, Illinois (personal communication).  Hudson River, New York (Mills, et al. 1996).  Lake Erie, Ohio (Mills et al. 1993).  Southern Lake Michigan, Illinois (personal communication).  Coastal waters of Washington (Ruiz and Hines 1997). Connecticut River between Hadley, Massachusetts and Hinsdale, New Hampshire (Smith et al. 2002).

Ecology: Cordylophora caspia lives in freshwater and brackish or slightly salty habitats.  Colonies grow on hard surfaces including rocks, pilings, and dreissenid mussel shells.  Can consume organisms 2–3 times the size of individual polyps by working together.

May benefit from the expansion of zebra nad quagga mussels (providing substrate) and from increased salinity in systems impacted by road salt (preference for higher salinity).


Means of Introduction: Aquarium release in Lake Erie (Mills et al. 1993).  Ballast water in Washington (Ruiz and Hines 1997). 

Status: Established in L. Erie (U.S. EPA 2008)

Impact of Introduction: Smith et al. (2002) described C. caspia as a 'benthic colonial predator' that preys upon chironomids and other larval insects. This may result in less prey availability for fish. The ecological impacts of C. caspia, however, have not yet been thoroughly studied. Uncolonized substrate introduced to C. caspia and subsequently colonizied had different realtive abundances of other invertebrates as compared to substrates not colonized by C. caspia (Ruiz et al. 1999). Other studies have suggested that C. caspia may contribute to a restructuring of benthic and pelagic freshwater communities (Folino 2000).

Competition for space, i.e. sutiable substrate for colonization, may occur between zebra mussel (Dreissena polymorpha) and C. caspia (Walton 1996, Folino 2000). Cordylophora caspia also typically eats zebra and quagga mussel larvae.

There is a negative economic impact associated with the biofouling caused by Cordylophora caspia (Folino 2000).

Remarks: Smith et al. (2002) noted that C. caspia shows morphological and ecological changes in habitats of lower salinity such as inland freshwaters. For example, growth rates decrease, reproductive rates decrease (sexually and asexually), polyp size changes, population density changes, and cell size and shape is altered (Smith et al. 2002 and references).

Cordylophora caspia is preyed upon by an introduced nudibranch (Tenellia adspersa) (Mills and Sommer 1995).

Cordylophora caspia is thought to be taxonomically synonymous with C. lacustris by many scientific researchers (Folino 2000 and references).

References: (click for full references)

Anderson, Roland C. "Nudibranchs: butterflies of the sea." International Zoo Yearbook34.1 (1995): 65-70. Web.

Berg, M.B., and N.C. Folino-Rorem. 2009. Alterations of Lake Michigan benthic communities by the invasive colonial hydroid, Cordylophora caspia: effects on fish prey. Unpublished report. Available:

Carlton, J.T., and M.H. Ruckelshaus. 1997. Nonindigenous marine invertebrates and algae. Pages 187-201 In: Simberloff, D., D.C. Schmitz, T.C. Brown (eds), Strangers in Paradise. Island Press, Washington, D.C.

Darling, J.A., and N.C. Forino-Rorem. 2009. Genetic analysis across different spatial scales reveals multiple dispersal mechanisms for the invasive hydrozoan Cordylophora in the Great Lakes. Molecular Ecology 18:4827-4840.

Folino, N.C. 2000. The freshwater expansion and classification of the colonial hydroid Cordylophora (Phylum Cnidaria, Class Hydrozoa). In Pederson, J. (ed.) Marine Bioinvasions: Proceedings of the First National Conference, January 24-27, 1999. Massachusetts Institute of Technology Sea Grant College Program, Cambridge, MA. pp. 139-144.

Gutierre, Silvia M. "PH Tolerance of the Biofouling Invasive Hydrozoan Cordylophora Caspia." Hydrobiologia 671 (2012): 91-95. Springer. Web.

Mant, R. C., G. Moggridge, and D. C. Aldridge. "Biofouling by Bryozoans, Cordylophora, and Sponges in UK Water Treatment Works." Water Science and Technology 63.9 (2011): 1815-822. Web.

Mills, C.E., and F. Sommer. 1995. Invertebrate introductions in marine habitats: two species of hydromedusae (Cnidaria) native to the Black Sea, Maeotias inexspectata and Blackfordia virginica, invade San Francisco Bay. Marine Biology 122:279-288.

Mills, E.L., M.D. Scheuerll, D.L. Strayer, and J.T. Carlton. 1996. Exotic species in the Hudson River basin: a history of invasions and introductions. Estuaries 19(4):814-823.

Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. 1993. Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions. Journal of Great Lakes Research 19(1):1-54.

Moreteau, J.C., and M. Khalanski. 1994. Settlings and growth of D. polymorpha in the raw water circuits of the Cattenom Nuclear Power Plant (Moselle, France). Proceedings of the Fourth International Zebra Mussel Conference, Madison, WI, March 1994. pp. 553-574.

Pennak, R.W. 1987. Coelenterata (Hydroids, Jellyfish). Pages 110-123 in Fresh-water Invertebrates of the United States, 3rd edition. John Wiley and Sons, Inc., New York. 628 p.

Portella, K.F., and A. Joukoski. 2009. Biofouling and chemical biodeterioration in hydroelectric power plant Portland cement mortar. Química Nova 32(4):1047-1051.

Ringelband, U., and L. Karbe. "Effects of Vanadium on Population Growth and Na-K-ATPase Activity of the Brackish Water Hydroid Cordylophora caspia." Bulletin of Environmental Contamination and Toxicology 57.1 (1996): 118-24. Web.

Ruiz, G.M., and A.H. Hines. 1997. The risk of nonindigenous species invasion in Prince William Sound associated with oil tanker traffic and ballast water management: pilot study. Prepared for the Regional Citizens' Advisory Council of Prince William Sound.

Ruiz, G.M., P. Fofonoff, and A.H. Hines. 1999. Non-indigenous species as stressors in estuarine and marine communities: assessing invasion impacts and interactions. Limnology and Oceanography 44(3, part 2):950-972.

Smith, D.G., S.F. Werle, and E. Klekowski. 2002. The rapid colonization and emerging biology of Cordylophora caspia (Pallas, 1771) (Cnidaria: Clavidae) in the Connecticut River. Journal of Freshwater Ecology 17(3):423-430.

U.S. Environmental Protection Agency (USEPA). 2008 Predicting future introductions of nonindigenous species to the Great Lakes. National Center for Environmental Assessment, Washington, DC; EPA/600/R-08/066F. Available from the National Technical Information Service, Springfield, VA, and

Walton, W.C. 1996. Occurrence of zebra mussel (Dreissena polymorpha) in the oligohaline Hudson River, New York. Estuaries 19(3):612-618.

Wurtz, C.B., and S.S. Roback. 1955. The invertebrate fauna of some Gulf Coast rivers.  Proceedings of the Natural Sciences Academy of Philadelphia 107:167-206.

Author: Fuller, P., E. Maynard, D. Raikow, J. Larson, T.H. Makled, and A. Fusaro

Revision Date: 5/24/2013

Citation Information:
Fuller, P., E. Maynard, D. Raikow, J. Larson, T.H. Makled, and A. Fusaro, 2018, Cordylophora caspia Pallas, 1771: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL,, Revision Date: 5/24/2013, Access Date: 1/22/2018

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.

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Citation information: U.S. Geological Survey. [2018]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [1/22/2018].

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