Invasion History

First Non-native North American Tidal Record: 1929
First Non-native West Coast Tidal Record: 1929
First Non-native East/Gulf Coast Tidal Record: 1977

General Invasion History:

The entoproct (or kamptozoan) Barentsia benedeni was first described from Ostende, Belgium in 1887, but its origin is unknown. It was found to be widespread in European waters, from the Baltic to the Mediterranean, Black and Caspian Seas, and later found on the coasts of Japan, Australia, and the East and West coasts of North America (Nielsen 1989; Wasson 1997). Because of this organism's small size, and the scarcity of people with taxonomic knowledge of this group, B. benedeni is likely to be overlooked at many sites, and may not have been recorded until long after its invasion.

North American Invasion History:

Invasion History on the West Coast:

On the U.S. Pacific coast, B. benedeni was first found in Lake Merritt, San Francisco Bay in 1929 (Cohen and Carlton 1995; Wasson 1997), and subsequently in Coos Bay, Oregon in 1988 (Carlton 1989); Elkhorn Slough, California in 1998 (Wasson et al. 2001); Puget Sound, Washington in 1998 (Cohen et al. 1998); and Humboldt Bay, California in 2000 (Boyd et al. 2002).

Invasion History on the East Coast:

Barentsia benedeni was collected in Vineyard Haven, Martha's Vineyard, Massachusetts in 1977 (Jebram and Everitt 1982), and also reported from 'Cape Cod' (possibly referring to the Martha's Vineyard record) (Nielsen 1989). It was not collected in previous studies of entoprocts in the Chesapeake Bay (Osburn 1944) or other historical East Coast sampling sites (Woods Hole, MA; North Carolina; South Carolina) (Wasson et al. 2000). In the Chesapeake Bay, B. benedeni was first identified on settling plates in 1994, in sites in the upper and lower Bay. In 1994-1996, it was collected in Baltimore Harbor and the Severn River, in Mobjack Bay, and Norfolk Harbor (Wasson et al. 2000). More recently, it has been collected in Long Island Sound (Canning and Carlton 2000; MIT Sea Grant 2003); Peconic Bay, Long Island (MIT Sea Grant 2003); and Narragansett Bay (MIT Sea Grant 2003).


Barentsia benedeni, like other entoprocts (also called kamptozoans) are colonial animals consisting of many zooids connected by a stolon. A zooid consists of a stalk, which is topped by the body of the animal, in a cup-shaped structure, called the calyx. The upper edge of the calyx bears 10-20 tentacles, surrounding the mouth, which faces upward. The upper surface of the body, surrounded by tentacles, includes both the mouth and the anus, leading to the term 'entoproct' (Barnes 1983).

In B. benedeni, the stalks are composed of segments, which consist of nodes, which are conical at each end and cylindrical in the middle portion, and are linked by rods. Animals from San Francisco Bay and Coos Bay typically had 3-5 nodes, but some specimens have up to 20 nodes in the stalk. The segments tend to be compressed and squat near the base, and more elongate and urn-like toward the calyx. The stalk narrows at the base of the calyx. The calyx is small (250-500 µm long) and compressed laterally, while the stalk is about 2-8 mm tall. This kamptozoan produces small yellowish hibernacula at the ends of short branches of the stolons- these are modified zooids for survival under adverse conditions (Nielsen 1989; Wasson 1997).

The colonies consist of a thick fuzz or fur of zooids, spreading over substrates. Budding can occur from the upper nodes, resulting in stolons which grow down to the substrate. This kamptozoan is typical of estuaries and harbors, often in brackish waters. It grows on and among other fouling organisms, such as barnacles, bryozoans, tube-dwelling polychaetes, and tunicates (Wasson 1997; Wasson et al. 2000).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Entoprocta
Order:   Pedicellinida
Family:   Pedicellinidae
Genus:   Barentsia
Species:   benedeni


Ascopodaria gracilis (Craig, 1929)
Barentsia gracilis (Hedgepeth, 1964)
Pedicellina benedeni (Foettinger, 1887)

Potentially Misidentified Species

Barentsia gracilis



The entoproct (or kamptozoan) Barentsia benedeni forms large, fuzzy colonies, reproducing asexually by budding new zooids from stolons. The zooids are hermaphroditic, and reproduce sexually on a seasonal basis, in winter and spring (February-July), in San Francisco Bay (Wasson 1997), or spring-fall, in Japan (Nielsen 1989). The eggs are brooded externally in the vestibule (inside the ring of tentacles) and hatch into lecithotrophic larvae which spend a few hours in the plankton (Marsical 1965). Barentsia benedeni is typical of harbors and estuaries, often in brackish waters (Neilsen 1989; Wasson 1997; Wasson et al. 2000).



Trophic Status:

Suspension Feeder



General HabitatCoarse Woody DebrisNone
General HabitatOyster ReefNone
General HabitatMarinas & DocksNone
General HabitatRockyNone
General HabitatCanalsNone
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Minimum Temperature (ºC)0Field data, based on occurrence of ice in northern localities (Nielsen 1989; Wasson 1997a; Wasson et al. 2000; Ruiz et al. unpublished data;)
Maximum Temperature (ºC)30Field data, Ruiz et al. unpublished data.
Minimum Salinity (‰)7Nielsen 1989; Wasson 1997a; Ruiz et al. unpublished data;
Maximum Salinity (‰)35Field data, probably occurs at higher salinities
Minimum Duration0.2Larval Period - In the one case where settlement of lab-reared larvae was observed, it took place 5 hours after expulsion from the brood pouch (Mariscal 1965). For most barentsiids, the planktonic period of the larvae is less than a day (Nielsen 1989).
Maximum Duration0.2Larval Period - In the one case where settlement of lab-reared larvae was observed, it took place 5 hours after expulsion from the brood pouch (Mariscal 1965). For most barentsiids, the planktonic period of the larvae is less than a day (Nielsen 1989).
Maximum Height (mm)8(Nielsen 1989; Wasson 1997).
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNoneMesohaline-Euhaline

General Impacts

Barentsia benedeni is an abundant, but easily overlooked fouling organism in its native and introduced ranges. No economic or ecological impacts have been reported.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEA-II None 1887 Crypto Estab
B-II None 0 Crypto Estab
B-III None 0 Crypto Estab
MED-IX None 1926 Crypto Estab
MED-VII None 1980 Crypto Estab
MED-II None 0 Crypto Estab
NA-ET3 Cape Cod to Cape Hatteras 1977 Def Estab
NEP-V Northern California to Mid Channel Islands 1929 Def Estab
NEP-IV Puget Sound to Northern California 1988 Def Estab
NEP-III Alaskan panhandle to N. of Puget Sound 1998 Def Estab
NWP-4b None 1944 Def Estab
CASP Caspian Sea 1965 Def Estab
AUS-VII None 1997 Def Estab
AUS-X None 1997 Def Estab
P170 Coos Bay 1988 Def Estab
M130 Chesapeake Bay 1995 Def Estab
M040 Long Island Sound 1998 Def Estab
P130 Humboldt Bay 2000 Def Estab
M020 Narragansett Bay 2000 Def Estab
P090 San Francisco Bay 1929 Def Estab
P080 Monterey Bay 1998 Def Estab
P290 Puget Sound 1998 Def Estab
M030 Gardiners Bay 2003 Def Estab
N195 _CDA_N195 (Cape Cod) 1977 Def Estab
MED-X None 0 Crypto Estab
P030 Mission Bay 2011 Def Estab
NEP-VI Pt. Conception to Southern Baja California 2011 Def Estab
P286 _CDA_P286 (Crescent-Hoko) 1999 Def Estab
M023 _CDA_M023 (Narragansett) 2019 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
27622 Foss 2009 2005 2005-09-09 San Mateo Bridge Def 37.5806 -122.2543
28823 Foss 2009) 2005 2005-10-20 San Pablo Bay Pumphouse Def 38.0446 -122.4326
29429 Foss 2009 2005 2005-09-07 Dumbarton Bridge Def 37.5070 -122.1168
29631 Cohen and Carlton, 1995 1977 1977-01-01 Salton Sea Def 33.2525 -115.7437
30885 Foss 2009 2005 2005-10-19 Hercules Wharf Def 38.0231 -122.2928
32624 Foss 2009 2005 2005-11-15 China Camp Def 38.0025 -122.4617
33085 Mariscal 1965; Carlton 1979 1929 1929-01-01 Lake Merritt Def 37.8040 -122.2578


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