The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Pectinatella magnifica
Pectinatella magnifica
(magnificent bryozoan)
Native Transplant

Copyright Info
Pectinatella magnifica (Leidy, 1851)

Common name: magnificent bryozoan

Taxonomy: available through www.itis.govITIS logo

Identification: Pectinatella magnifica is a species of freshwater bryozoan in the class Phylactolaemata. Like other species of bryozoans (also known as Ectoprocta or commonly as moss animals), the individual microscopic aquatic invertebrates (called a zooid) live directly on submerged surfaces in a colony (Ricciardi and Reiswig 1994, Wood 2010). Unlike other freshwater bryozoans, P. magnifica makes its own substrate, forming large gelatinous colonies that grow attached to submerged surfaces such as a rock or branch. The colonies can be transparent-to-brownish purple in color and can contain enormous numbers of zooids (Wilcox 1906, Ricciardi and Reiswig 1994, Wood 2010). The zooids grow in rosette-like patches over the gelatinous base and give the P. magnifica its unique pattern (Pennak 1989, Wood 2010). Each zooid has a horseshoe-shaped head-like structure (i.e., lophophore) that has a crown of 50-84 tentacles that filter food from the water (Ricciardi and Reiswig 1994, MDC 2017). The mouth is at the base of the tentacles and is encircled with red pigment (Ricciardi and Reiswig 1994, Wood 2010).

Size: On average, colonies are between 30-50 cm in diameter (Ricciardi and Reiswig 1994), but some can grow more than 60 cm in diameter (MDC 2017).

Native Range: Pectinatella magnifica is native to freshwater drainages of eastern North America from New Brunswick and Ontario, Canada; south to Florida and Mississippi. The native distribution spans throughout the Great Lakes region east of the Mississippi River mainstem (Pennak 1989, Wood 2010).

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Pectinatella magnifica are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AR201320192Lower Little Arkansas, Oklahoma; Petit Jean
CA2013202215Coyote; Honcut Headwaters-Lower Feather; Lower Sacramento; Mad-Redwood; North Fork American; Pajaro; Russian; Sacramento Headwaters; San Joaquin Delta; Tomales-Drake Bays; Upper Bear; Upper Cosumnes; Upper Mokelumne; Upper Stanislaus; Upper Tuolumne
ID199820205Coeur d'Alene Lake; North Fork Payette; Pend Oreille Lake; St. Joe; Upper Spokane
IA202020201Middle Iowa
LA201620206Amite; Bayou Sara-Thompson; Lake Maurepas; Liberty Bayou-Tchefuncta; Lower Ouachita; Tensas
MN201020194Lower Minnesota; Lower St. Croix; Twin Cities; Vermilion
MO201620214Harry S. Truman Reservoir; James; Lake of the Ozarks; Niangua
OR1998202319Alsea; Clackamas; Coast Fork Willamette; Coos; Illinois; Lower Columbia-Clatskanie; Lower Willamette; Middle Columbia-Hood; Middle Willamette; Necanicum; Siletz-Yaquina; South Santiam; South Umpqua; Tualatin; Umpqua; Upper Klamath; Upper Klamath Lake; Upper Willamette; Wilson-Trusk-Nestuccu
TX2007202012Buffalo-San Jacinto; Caddo Lake; Elm Fork Trinity; Leon; Lower Angelina; Lower Sulpher; Lower Trinity-Kickapoo; Middle Brazos-Palo Pinto; Spring; Upper West Fork Trinity; West Fork San Jacinto; Yegua
WA1998202321Banks Lake; Colville; Crescent-Hoko; Duwamish; Hoh-Quillayute; Lake Washington; Lower Columbia-Clatskanie; Lower Columbia-Sandy; Lower Cowlitz; Lower Skagit; Nisqually; Nooksack; Palouse; Puget Sound; Puyallup; Queets-Quinault; Snohomish; Strait of Georgia; Upper Chehalis; Upper Columbia-Priest Rapids; Upper Cowlitz
WI201620224Flambeau; La Crosse-Pine; Lower Chippewa; Upper Wisconsin

Table last updated 6/15/2024

† Populations may not be currently present.

Ecology: Pectinatella magnifica are typically found in lentic environments including freshwater lakes, ponds, and swamps, but can also be found in lotic environments (i.e., streams). The colonies are sessile with little preference among attaching surfaces (Joo et al. 1992), frequently found attached to rocks, wood, aquatic vegetation, pilings, or other submerged surfaces. On rare occasions the colonies will be found free-floating (Ricciardi and Reiswig 1994, Wood 2010, Joo et al. 1992). Pectinatella magnifica has been defined as a warm water species (Ricciardi and Reiswig 1994) although the species can display a wide temperature tolerance (4-32 °C) (Everitt 1975, Ricciardi and Reiswig 1994), but cannot tolerate saline waters (Everitt 1975).

Pectinatella magnifica can reproduce in several ways. Zooids can “clone” themselves by budding, but they can also create eggs and sperm and reproduce sexually. Pectinatella magnifica, like other freshwater bryozoans, can also form hard, round “statoblasts” which function like seeds. The creation of statoblasts is unique to bryozoans allowing them to endure variable and uncertain conditions of freshwater environments (Ricciardi and Reiswig 1994), although the statoblasts do not tolerate freezing temperatures (Wood pers. comm. 1997). Each statoblast can create a new colony (Ricciardi and Reiswig 1994). Pectinatella magnifica are known to have oscillating, annual population sizes in a waterbody. The current overwintering theory from Wood (pers. comm. 1997) is that statoblasts are created in the fall, which can disperse widely as the bryozoans decompose. The statoblasts attach to free clumps of algae or debris which then sinks to the bottom of the waterbody. The following spring, as that material decays, the statoblasts are released to float back to the surface and germinate. The summer germination produces quantities of "larvae," or little colonies that look like miniature blimps. The larvae are free-swimming for 2-24 hours and then settle on a suitable substrate and establish new colonies for a late summer statoblast-producing generation.

The individual P. magnifica zooids have mucous-coated tentacles that trap diatoms, phytoplankton, and other microscopic organisms, where cilia, or tiny hairs lining the tentacles, sweep the food to the mouth (Ricciardi and Reiswig 1994, Wood 2010). Individual zooids may filter an average of 8.8 ml of water/ day (Bullivant 1968).

Means of Introduction: Pectinatella magnifica has possibly been introduced by hitch hiking with stocked fishes, on aquatic plants, or on boats (Nehring 2002).

Status: Established in California, Idaho, Louisiana, Minnesota, Oregon, Texas, Washington and Wisconsin. The status of the specimens in Arkansas and Missouri are unknown.

Impact of Introduction: Pectinatella magnifica can become so abundant during warm months they have the potential to clog fishing nets, foul power plant water systems, and obstruct municipal water systems and other types of water pipes (Ricciardi and Reiswig 1994, Wood 2010).

Pectinatella magnifica can increase water clarity by removing large quantities of suspended material from the water including diatoms, suspended algae, and inorganic clay/silt. Over time, the clearer waters may promote algal and macrophytic growth that can restructure the ecosystem (Wood pers. comm. 1997). 

Pectinatella magnifica can serve as an intermediate host of Tetracapsuloides bryosalmonae, a myxozoan parasite that causes Proliferative Kidney Disease (PKD) in salmonids (Okamura and Wood 2002). PKD is especially problematic for rainbow trout (Oncorhynchus mykiss) aquaculture in the western U.S. (Merck 2015).

References: (click for full references)

Bullivant, J.S. 1968. The method of feeding of lophophorates (Bryozoa, Phoronida, Brachiopoda). New Zealand Journal of Marine and Freshwater Research 2(1):135-146.

Cauvel, K. 2017. Bryozoans found in Lake Sixteen. Skagit Valley Herald, Mount Vernon, WA. http://www.goskagit.com/news/bryozoans-found-in-lake-sixteen/article_2c2a4e51-3233-5e2d-a55f-1b845b2fcf38.html. Created on 08/27/2017. Accessed on 08/30/2017.

Everitt, B. 1975. Fresh-water Ectoprocta: distribution and ecology of five species in southeastern Louisiana. Transactions of the American Microscopical Society:130-134.

iMapInvasives. 2016. Oregon iMapInvasives. Oregon Biodiversity Information Center, Portland, OR. https://sites.google.com/site/orimapresources/. Accessed on 04/09/2015.

Joo, G., A. K. Ward, and G. M. Ward. 1992. Ecology of Pectinatella magnifica (Bryozoa) in an Alabama oxbow lake: colony growth and association with algae. Journal of North American Benthological Society 11(3):324-333.

Marsh, T. 2000. Bryozoan research at North Central College, Illinois.

Marsh, T., and T. S. Wood. 2002. Results of a freshwater bryozoan survey in the Pacific Northwestern United States. Pages 207-214 in Wyse Jackson, D. P., C. J. Buttler, and M. S. Jones., eds. Bryozoan Studies 2001. Balkema Publishers, Rotterdam, Netherlands.

Merck, Animal Health. 2015. Proliferative kidney disease (PKD). http://aqua.merck-animal-health.com/diseases/proliferative-kidney-disease/productadditional_127_113338.aspx. Accessed on 12/05/2017.

Missouri Department of Conservation (MDC). 2017. Bryozoans (moss animals) Freshwater species in the phylum Bryozoa. https://nature.mdc.mo.gov/discover-nature/field-guide/bryozoans-moss-animals. Accessed on 12/07/2017.

Nehring, S. 2002. Biological invasions into German waters: an evaluation of the importance of different human-mediated vectors for nonindigenous macrozoobenthic species. Pages 373-383 in Leppäkoski, E., S. Gollasch, and S. Olenin, eds. Invasive aquatic species of Europe: distribution, impacts, and management. Kluwer Adademic Publishers. Dordrecht, The Netherlands.

Okamura, B., and Wood T. S. 2002. Bryozoans as hosts for Tetracapsula bryosalmonae, the PKX organism. Journal of Fish Diseases 25:469-475.

Pennak, R.W. 1989. Fresh-water invertebrates of the United States, 3rd ed. John Wiley & Sons, New York.

Ricciardi, A., and H.M. Reiswig. 1994. Taxonomy, distribution, and ecology of the freshwater bryozoans (Ectoprocta) of eastern Canada. Canadian Journal of Zoology 72(2):339-359.

Sytsma, M.D., J.R. Cordell, J.W. Chapman, and R.C. Draheim. 2004. Lower Columbia River Aquatic Nonindigenous Species Survey 2001-2004. Final Technical Report. United States Coast Guard and the United States Fish and Wildlife Service. http://pdxscholar.library.pdx.edu/centerforlakes_pub/23.

United States Environmental Protection Agency (USEPA). 2017. STORET database.  http://www.epa.gov/storet. Accessed on 03/02/2017.

Wilcox, A.W. 1906. Locomotion in young colonies of Pectinatella magnifica. The Biological Bulletin 11(5):245-252.

Wood, T.S. 2010. Bryozoans. Pages 437-454 in Thorp, J.H., and A.P. Covich, eds. Ecology and classification of North American freshwater invertebrates. Academic Press, London, United Kingdom. London, UK.

Author: Daniel, W.M.

Revision Date: 2/20/2024

Citation Information:
Daniel, W.M., 2024, Pectinatella magnifica (Leidy, 1851): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=2335, Revision Date: 2/20/2024, Access Date: 6/15/2024

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.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [6/15/2024].

Contact us if you are using data from this site for a publication to make sure the data are being used appropriately and for potential co-authorship if warranted.

For general information and questions about the database, contact Wesley Daniel. For problems and technical issues, contact Matthew Neilson.