Invasion History

First Non-native North American Tidal Record: 1998
First Non-native West Coast Tidal Record: 1998
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Pectinatella magnifica is a freshwater bryozoan described by Joseph Leidy in 1851 from the Delaware River in the vicinity of Philadelphia. It is widespread in Eastern North America from New Brunswick and Ontario (Ricciardi and Reiswig 1994) to Louisiana and Texas (Everitt 1975). Pectinatella magnifica forms large colonies in nutrient-rich habitats and is favored by the formation of reservoirs and ponds. It is often reported in the press as a mysterious 'blob'. As with other freshwater bryozoans, its statoblasts are tolerant of desiccation. It has been introduced to Europe, Asia and the Western US.

North American Invasion History:

Invasion History on the West Coast:

Pectinatella magnifica had previously been considered to range only as far west as Texas, but Marsh and Wood (2002) found it in 18 locations in Washington and Oregon, including waters in arid interior regions and wetter coastal and mountain localities. Its occurrence in the West, including the Columbia River watershed is apparently the result of human activities. This bryozoan was found in several Oregon tributaries in 1998, including the head of tide in the Willamette and Columbia Rivers (Bonneville Dam) (Marsh and Wood 2002), and was collected in the tidal river in the Columbia Slough near Portland in 2002 (Sytsma et al. 2004). Biologists and boaters along the tidal Columbia River have noticed increasing abundance of P. magnifica (US. Fish and Wildlife Service 2012). In 2005, this bryozoan was found in the Sacramento-San Joaquin River Delta, at the Oxbow Marina, by a US Fish and Wildlife Service Survey. It is now abundant in low-salinity habits in the San Francisco estuary (Jimenez et al. 2018).

Invasion History Elsewhere in the World:

Pectinatella magnifica has been introduced to European fresh waters, including France, Germany, and the Netherlands, possibly by shipping, fish introductions, or the ornamental water plants trade (Nehring 2002). It has also recently been introduced to Japan and Korea (Seo 1998).


Pectinatella magnifica is a freshwater bryozoan which forms large, slimy, gelatinous, and transparent-to- brownish purple colonies up to 30-50 cm in diameter. Its zooids grow in rosette-like patches over a common gelatinous base. The lophophore bears 50-84 tentacles, and has conspicuous red pigment around the mouth. Its statoblasts are roughly circular, with a single row of flattened, hooked spines around the periphery (description from: Rogick 1935; Ricciardi and Reiswig 1994).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Bryozoa
Class:   Phylactolaemata
Order:   Plumatellida
Family:   Pectinatellidae
Genus:   Pectinatella
Species:   magnifica


Cristatella magnifica (Leidy, 1851)

Potentially Misidentified Species



Life History- Pectinatella magnifica is a globular, soft-bodied, freshwater bryozoan composed of many individual zooids. Living colonies have a bubbly surface texture and rosettes of zooids can clearly be seen. The zooids feed by extending the ciliated tentacles of the lophophore as a funnel, creating a current, and driving food particles into their mouths. The food is guided down the tentacles and through the pharynx by the cilia. Larger food particles can be moved or captured by flicking or contracting the tentacles. The zooids are hermaphroditic, and produce large eggs, which are released into an embryo sac in the body cavity. This develops into a ciliated cystid sac, which buds off several zooids. The sac is a small ciliated colony which swims for a short period (less than 1-2 days). The cystid sac settles and the ciliated outer wall degenerates. The new colony continues to grow, but the parent zooids die, so that only the tips of the colony contain living zooids. Colonies also produce asexual propagules, called statoblasts, masses of cells enclosed by a chitinous shell. Statoblasts remain dormant and are resistant to desiccation and freezing. They have great potential for dispersal (Barnes 1983). Colonies of Pectinatella magnifica die off in winter. Dying or dead colonies in autumn become smooth, slimy and transparent masses of gelatin, peppered with black statoblasts. (Ricciardi and Reiswig 1994; Judy Winston, personal communication).

Ecology- Pectinatella magnifica inhabits lakes and rivers, at 6.8-9.4 pH and 4-32 °C (Everitt 1975; Ricciardi and Reiswig 1994). It has been found attached to rocks, wood, aquatic vegetation, sponges, freshwater mussels, and other bryozoans (Ricciardi and Reiswig 1994).




caddisflies, crayfish, fishes

Trophic Status:

Suspension Feeder



General HabitatNontidal FreshwaterNone
General HabitatFresh (nontidal) MarshNone
General HabitatCoarse Woody DebrisNone
General HabitatTidal Fresh MarshNone
General HabitatCanalsNone
Salinity RangeLimnetic0-0.5 PSU
Salinity RangeOligohaline0.5-5 PSU
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Minimum Temperature (ºC)0Field- Based on occurrence in Canadian lakes.Large colonies break up at 10-12 C, but smaller colonies in Quebec tolerate 9 C. Statoblasts tolerate temberatures below freezing (Ricciardi and Reiswig 1994).
Maximum Temperature (ºC)32Field, Louisiana, Everitt 1975
Minimum Salinity (‰)0This is a freshwater species.
Maximum Salinity (‰)0.4Field, Louisiana, Everitt 1975
Minimum pH6.8Field, Ricciardi and Reiswig 1994
Maximum pH9.4Field, Ricciardi and Reiswig 1994
Minimum Reproductive Temperature9Field, in Canadian lakes (Ricciardi and Reiswig 1994)
Maximum Length (mm)1,300'I've seen colonies at least 4 feet high attached to boathouse pilings in a Virginia lake in autumn.' (Judy Winston, personal communication)
Minimum Height (mm)60Colony height, Wood 1989
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNoneNontidal Limnetic-Tidal Limnetic

General Impacts

Freshwater bryozoans, such as Pectinatella magnifica, sometimes become so abundant that they clog fishing nets, foul power plant water systems, and obstruct municipal water systems (Ricciardi and Reiswig 1994). However, impacts have not been reported from the Columbia River (Systma et al. 2004).

Parasite/Predator Vector: Pectinatella magnifica is one of many freshwater bryozoans which may serve as an intermediate host of Tetracapsula bryosalmonae, a myxozoan parasite which causes Proliferative Kidney Disease in salmonids. However, it was found in only one of the surveyed hatcheries (Folsom Lake, California) which had an outbreak of the disease. Other bryozoans may be more frequent hosts of this parasite (Okamura and Wood 2002).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
P260 Columbia River 1998 Def Estab
GL-I Lakes Huron, Superior and Michigan 0 Native Estab
GL-II Lake Erie 0 Native Estab
GL-III Lake Ontario 0 Native Estab
M090 Delaware Bay 0 Native Estab
M130 Chesapeake Bay 0 Native Estab
L095 _CDA_L095 (Cedar-Portage) 0 Native Estab
L014 _CDA_L014 (Beartrap-Nemadji) 0 Native Estab
P090 San Francisco Bay 2005 Def Estab
NA-S3 None 0 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
767939 Ruiz et al., 2015 2011 2011-09-26 Pittsburg Marina, San Francisco Bay, CA, California, USA Def 38.0346 -121.8829
768257 Ruiz et al., 2015 2012 2012-09-10 Sacramento Marina, San Francisco Bay, CA, California, USA Def 38.5648 -121.5184
768260 Ruiz et al., 2015 2012 2012-09-13 Port of Stockton, San Francisco Bay, CA, California, USA Def 37.9589 -121.3609


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