Invasion History

First Non-native North American Tidal Record: 1951
First Non-native West Coast Tidal Record: 1951
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Conopeum tenuissimum is an encrusting bryozoan occurring on docks, pilings, breakwaters, oysters, seagrasses, and other surfaces in estuarine habitats. It is native to the Northwestern Atlantic, where it occurs from Great Bay, New Hampshire and Boston Harbor to the Gulf of Mexico and Lake Maracaibo, Venezuela (Osburn 1944; Maturo 1958; Wass 1972; Dudley 1973; Winston 1977; Winston 1982; MIT Sea Grant 2003; Ruiz et al., unpublished data).

North American Invasion History:

Invasion History on the West Coast:

Conopeum tenuissimum was first identified from San Francisco Bay by Patricia L. Cook based on material collected in the estuarine Lake Merritt, Oakland, California (Carlton 1979; Cohen and Carlton 1995) in 1962 (J.T. Carlton, personal communication, 2013). It is likely that earlier records of brackish water Conopeum in the Bay, such as that of Filice (1959, as Conopeum commensale) are C. tenuissimum. It was probably introduced in the 19th century with oysters from the East Coast (Carlton 1979). It ranges from the central Bay (Oakland and the Presidio Yacht Club) to Carquinez Straits, at the head of San Pablo Bay, and well into brackish waters on the Petaluma River (Cohen and Chapman 2005; Cohen et al. 2005).

This bryozoan is also established in Elkhorn Slough, where it was found during a 1998 survey (Wasson et al. 2001). A bryozoan identified as ‘possibly C. tenuissimum’ was found in 'marinas around the bay' in Humboldt Bay in 2000 (Boyd et al. 2002). In Coos Bay, Oregon, C. tenuissimum was first collected in 1970, and is now common in the estuary (Carlton 1989; de Rivera et al. 2005).

Invasion History Elsewhere in the World:

Conopeum tenuissimum is established in estuaries in Nigeria and Ghana, in West Africa (Cook 1968; Cook 1985) and in Port Hacking, in Sydney Harbor, Australia (Vail and Wass 1981; Australian Museum Business Services 2002). 


Colonies of Conopeum tenuissimum form lacy white crusts on seagrasses, oysters, docks, pilings, breakwaters and other hard substrates. Sometimes colonies are pink or tan, due to food in the intestine or sediment caught in the spines. Colonies vary greatly in size and shape depending on the type of substratum. Zooids are typically 530 µm X 250 µm, and elongate-oval in shape. There is a single pair of spines at the distal end of the zooid, and 5-7 pairs of lateral spines. The polyps have ~11-15 tentacles. The budding pattern in Florida populations is that the ancestrula produces one distal primary bud, followed by proximal secondary buds, so that the colony initially develops a 'double-fan' pattern spreading from the two ends of the ancestrula. This eventually develops into a circular pattern as the colony grows. Compared to specimens from Florida identified as C. seurati, C. tenuissimum has larger zooids, and a more regular colony arrangement, heavier calcification, and more lateral spines (description from: Osburn 1944; Winston 1982; Winston and Hayward 2012). Conopeum is a difficult genus, and identifications of C. tenuissimum are frequently somewhat tentative (Cohen and Carlton 1995, Linda McCann, personal communication, 2011).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Bryozoa
Class:   Gymnolaemata
Order:   Cheilostomata
Suborder:   Anasca
Family:   Membraniporidae
Genus:   Conopeum
Species:   tenuissimum


Membranipora crustulenta (Osburn, 1944)
Membranipora tenuissima (Canu, 1908)

Potentially Misidentified Species

Conopeum chesapeakensis
NW Atlantic species, introduced to San Francisco Bay.

Conopeum commensale
Early (1950s) records (Filice 1959; Aldrich 1961, ciited by Carlton 1979) of 'C. commensale' probably refer to C. tenusissimun. Conopeum commensale is a widespread tropical species (Cohen and Carlton 1995).

Conopeum osburni
NE Pacific genus

Conopeum seurati
NE Atlantic species

Electra crustulenta
Misidentification in guide for Chesapeake Bay species, as Membranipora crustulenta (Osburn 1944)



Life History- Conopeum tenuissimum is an encrusting, calcified bryozoan colony composed of many individual zooids. 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 along the tentacles and through the pharynx by the cilia. Larger food particles can be moved or captured by flicking or contracting the tentacles (Barnes 1983). Larvae of C. tenuissimum are planktotrophic, but probably have a shorter planktonic period than Membranipora spp. (Dudley 1973; Winston and Hayward 2012). Larvae settle on a substrate and metamorphose into the first zooid of a colony, an ancestrula (Dudley 1973; Barnes 1983).

Ecology- Conopeum tenuissimum is common in brackish water (Osburn 1944) and is known from eelgrass beds, oyster beds, pilings, shells and pebbles (Osburn 1944; Dudley 1973; Winston 1982).



Trophic Status:

Suspension Feeder



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

Tolerances and Life History Parameters

Minimum Salinity (‰)6Field data (Osburn 1944)
Maximum Salinity (‰)37Field data (Cook 1985)
Broad Temperature RangeNoneCold temperate-Tropical
Broad Salinity RangeNoneMesohaline-Euhaline

General Impacts

Conopeum tenuissimum is a common fouling organism in its introduced range, including San Francisco Bay, Coos Bay, and Sydney Harbor (Vail and Wass 1981; Carlton 1989; Cohen and Carlton 1995), but specific economic or ecological impacts have not been reported.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NA-ET3 Cape Cod to Cape Hatteras 0 Native Estab
NA-ET2 Bay of Fundy to Cape Cod 0 Native Estab
CAR-VII Cape Hatteras to Mid-East Florida 0 Native Estab
CAR-I Northern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern Florida 0 Native Estab
WA-II None 1959 Def Estab
AUS-X None 1977 Def Estab
NEP-V Northern California to Mid Channel Islands 1951 Def Estab
NEP-IV Puget Sound to Northern California 1970 Def Estab
CAR-III None 0 Native Estab
P170 Coos Bay 1970 Def Estab
P090 San Francisco Bay 1951 Def Estab
P080 Monterey Bay 1998 Def Estab
P130 Humboldt Bay 2000 Def Estab
P093 _CDA_P093 (San Pablo Bay) 1951 Def Estab
P058 _CDA_P058 (San Pedro Channel Islands) 2011 Def Unk
NEP-VI Pt. Conception to Southern Baja California 2011 Def Unk

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
767361 Ruiz et al., 2015 2012 2012-08-22 Tomales-Marshall, Bodega Bay, California, USA Def 38.1514 -122.8888
767390 Ruiz et al., 2015 2012 2012-08-16 Tomales-SNPS, Bodega Bay, California, USA Def 38.1359 -122.8719
767797 Ruiz et al., 2015 2011 2011-09-15 Richmond Marina Bay Yacht Harbor, San Francisco Bay, CA, California, USA Def 37.9117 -122.3494
767810 Ruiz et al., 2015 2011 2012-09-20 San Leandro Marina, San Francisco Bay, CA, California, USA Def 37.6979 -122.1912
767841 Ruiz et al., 2015 2011 2011-09-16 Loch Lomond Marina, San Francisco Bay, CA, California, USA Def 37.9724 -122.4796
767850 Ruiz et al., 2015 2011 2011-09-13 Oyster Point Marina, San Francisco Bay, CA, California, USA Def 37.6725 -122.3864
767895 Ruiz et al., 2015 2011 2011-09-27 Vallejo Marina, San Francisco Bay, CA, California, USA Def 38.1086 -122.2694
767957 Ruiz et al., 2015 2011 2011-09-28 Benicia Marina, San Francisco Bay, CA, California, USA Def 38.0453 -122.1561
768030 Ruiz et al., 2015 2012 2012-08-27 Port of San Francisco Pier 31, San Francisco Bay, CA, California, USA Def 37.8078 -122.4060
768052 Ruiz et al., 2015 2012 2012-09-11 Ballena Isle Marina, San Francisco Bay, CA, California, USA Def 37.7676 -122.2869
768074 Ruiz et al., 2015 2012 2012-08-30 Oyster Point Marina, San Francisco Bay, CA, California, USA Def 37.6633 -122.3817
768122 Ruiz et al., 2015 2012 2012-09-04 Redwood City Marina, San Francisco Bay, CA, California, USA Def 37.5023 -122.2130
768225 Ruiz et al., 2015 2012 2012-09-13 San Leandro Marina, San Francisco Bay, CA, California, USA Def 37.6962 -122.1919
768265 Ruiz et al., 2015 2013 2013-08-15 Ballena Isle Marina, San Francisco Bay, CA, California, USA Def 37.7656 -122.2858


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