Blackfordia virginica

Invasion History

First Non-native North American Tidal Record: 1904
First Non-native West Coast Tidal Record: 1970
First Non-native East/Gulf Coast Tidal Record: 1904

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General Invasion History:

The medusa of the hydrozoan Blackfordia virginica was first collected in Norfolk Harbor, Virginia, in 1904, and described by Mayer (1910). Mayer also collected this species off Sandy Hook, New Jersey (as B. manhattensis, Mayer 1910). Blackfordia virginica's native distribution includes the Black Sea and the Sea of Azov (Thiel 1935; Naumov 1969; Mills and Sommer 1995), but canals enabled it to invade the Caspian Sea in 1956 (Logvinenko 1959). Based on the abundance of polyps and medusae in the Black Sea, Thiel (1935) considered that it was part of an endemic 'Sarmatic' cnidarian fauna, and only recently introduced to the United States. This was based on B. virginica's absence in early American collections (of Agassiz, Fewkes, Hargitt, etc.) and the lack of records of polyps from North America. It should be noted that Russian and Ukrainian workers consider B. virginica to be of Northwest Atlantic origin and introduced to the Black Sea (Mordukhai-Boltovskoi 1964; Goumiou et al. 2002). Provisionally, we are following Mills and Sommer (1995) and Ruiz et al. (2000) in treating this species as having a Black Sea origin. A genetic analysis by Harrison et al. (2013) found that North American populations had a very low genetic diversity, compared to that of 30 other hydrozoan species. There were no differing haplotypes among populations in four US estuaries on the East, Gulf, and West coasts, supporting the possibility of a single introduction to North America, and subsequent spread (Harrison et al. 2013).

Blackfordia virginica has been reported from European Atlantic estuaries, including the Loire, France; the Mira, Portugal (in 1984, Moore 1987); and the Guadiana estuary, Spain (Chícharo et al. 2009). It has also been found in the Caspian Sea (Logvinenko 1959), South America (Brazil in 1963, Argentina in 1983), India (in 1958, 1968, 1970; Moore 1987) and China (Chen-tsu & Chin 1962, cited by Bardi and Marques 2009). More recently, records have been reported from tropical Pacific Mexico (Alvarez 1998) and South Africa (Buecher et al. 2005). In the United States, B. virginica medusa were collected from tributaries of San Francisco Bay in 1993 and found in preserved samples from 1970 and 1974. Medusa have also been collected from Coos Bay, Oregon (in 1997; James T. Carlton, personal communication). Polyps were found in San Francisco Bay (Mills and Sommer 1995; Mills and Rees 2000), and in 1999 were reported from Baltimore Harbor in Chesapeake Bay (Ruiz et al., unpublished data). It is likely to have been widely transported in ballast water and fouling.

A genetic analysis by Harrison et al. (2013) found that North American populations had a very low genetic diversity, compared to that of 30 other hydrozoans. There were no differing haplotypes among populations in four US estuaries, on the East, Gulf, and West coasts, supporting the possibility of a single introduction to North America, and subsequent spread (Harrison et al. 2013).

North American Invasion History:

Invasion History on the West Coast:

Blackfordia virginica medusae were found in preserved samples collected in 1970-1974 from the Napa and Petaluma Rivers, brackish tributaries of San Francisco Bay. In 1992-1994, live medusae were studied (Mills and Sommer 1995), and in 1997 living polyps were found in the Napa River (Mills and Rees 2000). In fouling plate surveys in 2007 and 2008, polyps were collected in largest numbers in the Napa River, but were also found in the Petaluma River, Boynton Slough, and Montezuma Slough on the seaward edge of the Sacramento-San Joaquin Delta. Medusae occurred in the more saline portions of Suisun Marsh (6-16 PSU), but usually at low densities (0.1-.5 m^-3) (Schroeter 2008). Settlement of polyps occurred in June-October, and was optimum at a salinity of 14-22 PSU (Wintzer et al. 2011a). The only other West Coast system where B. virginica has been reported is Coos Bay, Oregon. In 1997, a single medusa was collected in Isthmus Slough, Coos Bay (James T. Carlton, personal communication). In 1999, hundreds of medusae were seen there (Mills and Rees 2000).

Invasion History on the East Coast:

The medusa of B. virginica was first collected and described in Hampton Roads, Virginia in 1904, and was reported as occurring northwards from Delaware Bay to Sandy Hook, New Jersey (as B. manhattensis; Mayer 1910). It was also collected in Norfolk Sound, Virginia in 1920-21 (Cowles 1930), but was not found in later extensive surveys by Calder (Calder 1971; Calder 1972). However, medusae were collected in the Mattaponi River, a York River tributary, in 2010 (Harrison et al. 2013). In South Carolina estuaries, B. virginica medusae were reported as occurring in 'numerous areas', and as abundant and widespread (Calder and Hester 1978). In the Delaware Bay, they were described as sporadic throughout the estuary (Cronin et al. 1962). Ferrante (1970) found the medusae to be abundant around 'Artificial Island', near the mouth of the Chesapeake and Delaware Canal. Harrison et al. (2013) collected specimens at Slaughter Beach, in lower Delaware Bay in 2010. It was found in the Mullica River, in the New Jersey coastal bay system (Richards 1938), and has been reported from mesohaline waters of the Hudson River estuary (Patrick 1994). The scattered records of this medusa suggest a patchy spatial distribution and/or an eruptive population cycle on the East Coast. The only collection of polyps is from fouling plates in Baltimore Harbor, identified by Dale Calder (Royal Ontario Museum, Toronto, Canada).

Invasion History on the Gulf Coast:

In 2009, medusae of B. virginica were collected in Lake Pontchartrain, Louisiana (Harrison et al. 2013). This medusa was collected much earlier on the Gulf in Laguna Tamiahua, in Veracruz, Mexico (Signoret-Poillón 1969, cited by Alvarez et al. 2003).

Invasion History Elsewhere in the World:

In Europe, B. virginica is known from one specimen collected in the Loire estuary, France (Denayer 1973), and from established populations in the Mira estuary, Portugal (Moore 1987) and the Gaudiana estuary, Spain (Chicaro et al. 2008), where it was discovered in 1984 and 2008, respectively. In 2013, medusae and polyps were discovered in the North Sea Canal (Noordzeekanaal), connecting Amsterdam to the North Sea (Faasse and Melchers 2014). It is abundant in lagoons adjacent to the Black Sea, and in the Sea of Azov (Thiel 1935; Naumov 1969), where we consider it native. It was introduced to the Caspian Sea in 1956, probably by ships entering through canals from the Black Sea (Logvinenko 1959; Aladin et al. 2002). While many records are estuarine, and occasionally neritic (near-shore), its 1991 record off the east coast of South Africa is unusual in that it occurs in a strong ocean current (Agulhas Current) off an open coast (Buecher et al. 2005). Records in Asia are scattered, and include records from Bombay, Cochin, the Ganges estuary, and the Fujian Coast of China, from 1956 to the present (Moore 1987; Bardi and Marques 2009). In South America, B. virginica was first reported in Muribeca, near Recife, in the River Jaboatao (8⁰S) (in 1963, Moore 1987). It is established in northeastern Brazil, in several estuaries in Pernambuco and Sergipe states (Freire et al. 2013). In 1983, this medusa was found in the Rio de la Plata estuary, Argentina (36⁰S) (Genzano et al. 2006), and it has subsequently been found in several locations in southern Brazil (Nogueira and De Oliveira 2006; Bardi and Marques 2009). It is also known from Laguna Tamiahua, in Veracruz, Mexico (Signoret-Poillón, 1969, cited by Alvarez et al. 2003). So far, we know of only one record from the tropical Eastern Pacific, from a lagoon in Chiapas, Mexico in 1997 (Alvarez 1999).

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Description

The hydroid colonies of Blackfordia virginica are creeping, and arise from a stolon.The stems are occasionally branched, and can bear 2-3 hydrothecae on each stem. The stem and lower stalk sometimes have weak annular constrictions (rings). The hydrothecae are cylindrical, rising vertically above the stalk. The hydrotheca abruptly widens from the stalk, and is separated from it by a diaphragm. The mouth of the hydrotheca can be closed by an operculum, consisting of numerous triangular flaps meeting centrally and having no clear demarcation from the hydrothecal margin. The hydranth ends in a conical hypostome with a whorl of 12-16 filiform tentacles, connected at their base by an intertentacular membranous web. Gonophores develop on the stolon or on the stalk of the hydranths. They are pear-shaped sacs, containing one medusa at a time. The height of the hydrotheca without the stalk is 0.4-0.5 mm, while the gonothecae are about 0.45 mm. The total height of the hydroid is approximately 1-2 mm (description from: Naumov 1969; Mills and Sommer 1995; Bouillon et al. 2004; Bardi and Marques 2009). Polyps tend to grow on aquatic vegetation, barnacle shells, and the undersides of hard substrates (Naumov 1969; Wintzer et al. 2011a).

The medusa of B. virginica is dome-shaped, a little taller than a hemisphere, with a rounded apex. The jelly in the bell is thick, and composes nearly half the height of the bell. There are usually four radial canals, and a prominent ring canal around the base of the bell. The margin of the bell has a thin velum, which covers about 10-25% of the bell opening. The gonads extend from the manubrium along the radial canals, and cover up to about 2/3 of their length. In females, the gonads are granular and contain visible eggs, while in males they are linear and homogeneous.The medusa has a narrow, short manubrium, whose mouth has four long, fluted lips, with ruffled edges. There are 50-142 marginal tentacles, and between the roots of the tentacles are marginal statocysts. These frequently, but not always, contain black pigment and have a finger-like projection pointing towards the bell roof. Mature medusae are 4-22 mm (rarely exceeding 14-15 mm) in diameter and about 3-7 mm in height (description from: Mayer 1910; Naumov 1969; Moore 1987; Mills and Sommer 1995; Bouillon et al. 2004; Johnson and Allen 2005; Genzano et al. 2006; Bardi and Marques 2009).

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Taxonomy

Ecology

General:

Blackfordia virginica has a conspicuous planktonic medusa stage, and a small obscure hydroid stage. The hydroid grows in a creeping fashion, with short stalks and polyps about 1-2 mm high, attached to vegetation or other surfaces (including fouling plates and barnacle shells). Gonophores bud off the stems, and each one releases a single planktonic medusa, which drifts in the plankton. The medusa feeds on zooplankton, and grows, developing either ovaries or testes (Naumov 1969; Mills and Sommer 1995; Bardi and Marques 2009; Wintzer et al. 2011b). In the Napa and Petaluma Rivers, the most common foods were copepod nauplii, cyclopoid copepods, and mysids (Wintzer et al. 2013). Eggs hatch into non-feeding, ciliated planula larvae, which settle about four days after fertilization and grow into polyps.

In the San Francisco estuary, polyps showed a preference for settling on the undersides of surfaces, probably as a way of avoiding being covered by sediment. Recruitment of B. virginica polyps was highest during periods of higher water clarity (Wintzer et al. 2011a). Polyps have only been reported from estuarine habitats, over a salinity range of 3-22 PSU (Naumov 1969; Wintzer et al. 2011a), but the medusae have been found in open waters off the coast of New Jersey (Mayer 1910, as B. manhattensis) and in the Agulhas Current, off South Africa (Buecher et al. 2005), as well as in brackish waters down to 2 PSU (Nogueira and De Oliveira 2006).

Food:

Zooplankton

Trophic Status:

Carnivore

Carn

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Habitats

General Habitat	Grass Bed	None
General Habitat	Marinas & Docks	None
General Habitat	Coarse Woody Debris	None
General Habitat	Vessel Hull	None
Salinity Range	Oligohaline	0.5-5 PSU
Salinity Range	Mesohaline	5-18 PSU
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None
Vertical Habitat	Planktonic	None

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Tolerances and Life History Parameters

Minimum Temperature (ºC)	3	Field, Cronin et al. 1962, winter temperature in zone where B. virginica appeared in summer.
Maximum Temperature (ºC)	29.9	Field, Feire et al. 2013
Minimum Salinity (‰)	2	Medusae (Nogueira and De Oliveira 2006; Moore 1987). Polyps have been reported at 3-22 PSU (Naumov 1969; Schroeter 2008; Wintzer et al. 2011). In Suisun Marsh CA, medusae were not found at salinities below 5.6 PSU, and were most abundant at 6-16 PSU (Schroeter 2008).
Maximum Salinity (‰)	35	Medusa (Moore 1987)
Minimum Dissolved Oxygen (mg/l)	4.3	Field, Suisun Marsh (Schroeter 2008)
Maximum Length (mm)	7	Medusa height. Hydroids are 1-2 mm in height (Mayer 1910; Naumov 1969; Moore 1987; Mills and Sommer 1995).
Maximum Width (mm)	22	Medusa diameter- rarely exceeding 14-15 mm. (Naumov 1969; Moore 1987; Mills and Sommer 1995; Bouillon et al. 2004; Genzano et al. 2006; Bardi and Marques 2009; Wintzer et al. 2013)
Broad Temperature Range	None	Cold temperate-Tropical
Broad Salinity Range	None	Oligohaline-Euhaline

General Impacts

Blackfordia virginica, together with other introduced hydrozoans in brackish estuaries (e.g. Moerisia spp., Cordylophora caspia, Maeotias marginata), has the potential to alter planktonic food webs through predation on zooplankton. Most estuaries have few or no native brackish-water hydrozoans (Calder 1971; Calder 1972; Rees and Gershwin 2000; Wintzer et al. 2013). Sharp reductions in zooplankton abundance were observed during a Blackfordia bloom in the Guadiano estuary, Spain (Chícharo et al. 2009). However, measurements of feeding rate were not made, and the role of predation was not established. The extent and importance of hydrozoan predation in zooplankton populations has rarely been determined.

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References

Pinon-Gimate, Alejandra; ServiereZaragoza, Elisa; Ochoa-Izaguirre, Mar?a Paez-Osuna, Federico (2008) Species composition and seasonal changes in macroalgal blooms in lagoons along the southeastern Gulf of California, Botantic Marina 51: 112-123

Aladin, Nikolai V.; Plotnikov, Igor S.; Filipov, Andrei A. (2002) Invasive aquatic species of Europe: Distribution, impacts, and management., Kluwer Academic Publishers, Dordrecht. Pp. 351-359

Alvarez Silva, Carlos (1999) [Blackfordia virginica (Leptomedusae: Lovenellidae) in Mexican Pacific coastal lagoons], Revista de Biologia Tropical 47(1-2): 281

Álvarez Silva, Carlos; Gómez Aguirre, Samuel; Miranda Arce, Guadalupe (2003) [Morphological variations in Blackfordia virginica (Hydroidomedusae: Blackfordiidae) in coastal lagoons of Chaipis, Mexico], Revista de Biologia Tropical 51(2): 409-412

Backus, Andrew 08/13/2009 Final Programatic Environmental Impact Statement for Oyster Restoration in Chespaeake Bay. https://www.nao.usace.army.mil/Portals/31/docs/civilworks/oysters/oysterdecision.pdf



Bardi, Juliana; Marques, Antonio Carlos (2009) The invasive hydromedusae Blackfordia virginica Mayer, 1910 (Cnidaria: Blackfordiidae) in southern Brazil, with comments on taxonomy and distribution of the genus Blackfordia., Zootaxa 2198: 41-50

Bouillon, Jean; Medel, Maria Dolores; Pagès, Francesc; Gili, Josep-Maria; Boero, Ferdinando ; Gravili, Cinzia (2004) Fauna of the Mediterranean Hydrozoa., Scientia Marina 68(suppl. 2): 5-438

Buecher, Emmanuelle; Goy, Jacqueline; Gibbons, Mark J. (2005) Hydromedusae of the Agulhas Current, African Invertebrates 46: 27-69

Calder, Dale R. (1971) Hydroids and hydromedusae of southern Chesapeake Bay., Virginia Institute of Marine Science, Special Papers in Marine Science 1: 1-125

Calder, Dale R. (1972) Phylum Cnidaria, Special Scientific Report, Virginia Institute of Marine Science 65: 97-102

Calder, Dale R.; Carlton, James T.; Larson, Kristen; Mallinson, Jenny J.; Choong, Henry H. C.; Keith, Inti; Ruiz, Gregory M. (2019) Hydroids (Cnidaria, Hydrozoa) from marine fouling assemblages in the Galápagos Islands, Ecuador, Aquatic Invaders 14: 21-58

Calder, Dale R.; Hester, Betty S. (1978) Phylum Cnidaria., In: Zingmark, Richard G.(Eds.) An Annotated Checklist of the Biota of the Coastal Zone of South Carolina. , Columbia. Pp. 87-93

Chainho, Paula and 20 additional authors (2015) Non-indigenous species in Portuguese coastal areas, lagoons, estuaries, and islands, Estuarine, Coastal and Shelf Science <missing volume>: <missing location>

Chang, Andrew Louis (2009) <missing title>, University of California at Davis, Davis CA. Pp. <missing location>

Chia, Fu-Shiang; Rostron, M. A. (1970) Some aspects of the reproductive biology of Actinia equina (Anthozoa), Journal of the Marine Biological Association of the United Kingdom 50: 252-264

Chícharo, Maria Alexandra; Leitão, Tânia; Range, Pedro; Gutierrez, Cristina; Morales, Jesus; Morais, Pedro; Chícharo, v (2009) Alien species in the Guadiana Estuary (SE-Portugal/SW-Spain): Blackfordia virginica (Cnidaria, Hydrozoa) and Palaemon macrodactylus (Crustacea, Decapoda): potential impacts and mitigation measures, Aquatic Invasions 4(3): 501-506

Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>

Cowles, R.P. (1930) A biological study of the offshore waters of Chesapeake Bay, United States Bureau of Fisheries Bulletin 46: 277-381

Cronin, L. E.; Daiber, Joanne C.; Hilbert, E. M. (1962) Quantitative seasonal aspects of zooplankton in the Delaware River Estuary, Chesapeake Science 3(2): 63-93

Denayer, Jean-Claude (1973) Trois meduses nouvelles ou peu connues des cotes francaises: Maeotias inexspectata Ostrooumov, 1896, Blackfordia virginica Mayer, 1910, Nemopsis bachei Agassiz, 1849, Cahiers de Biologie Marine 14: 285-294

Faasse, Marco; Melchers, Martin (2014) The exotic jellyfish Blackfordia virginica introduced into the Netherlands (Cnidaria: Hydrozoa), Nederlandse Faunistiche Mededelingen 43: 104-109

Ferrante, John G. (1970) A quantitative study of the zooplanbkton in the Delaware River in the vicinity of Artificial Island in 1970., In: (Eds.) Ecological study of the Delaware River in the vicinity of Artificial Island.. , Middletown, Delaware.. Pp. <missing location>

Freire, Milena; Genzano, Gabriel Nestor; Neumann-Leitao, Sigrid; Perez, Carlos Daniel (2013) The non-indigenous medusa Blackfordia virginica (Hydrozoa, Leptothecata) in tropical Brazil: 50 years of unnoticed presence, Biological Invasions Published online: <missing location>

Genzano, Gabriel; Mianzan, Hermes; Acha, Eduardo M.; Gaitan. Esteban. (2006) First record of the invasive medusa Blackfordia virginica (Hydrozoa: Leptomedusae) in the Río de la Plata estuary, Argentina-Uruguay., Revista Chilena de Historia Natural 79: 257-261

Gomiou, Marian-Traian; Alexandrov, Boris; Shadrin, Nikolai; Zaitsev, Yuvenaly (2002) The Black Sea- a recipient, donor, and transit area for alien species., In: Leppakoski, E.; Gollasch, S.; Olenin, S.(Eds.) Invasive aquatic species of Europe: Distribution, impacts, and management.. , Dordrecht. Pp. 341-350

Harrison, Genelle F.; Kim, Kiho; Collins, Allen G. (2013) Low genetic diversity of the putatively introduced, brackish water hydrozoan, Blackfordia virginica (Leptothecata: Blackfordiidae), throughout the United States, with a new record for Lake Pontchartrain, Louisiana, Proceedings of the Biological Society of Washington 126(2): 91-102

Huang, Xuguang, Bingyu;; Guo, Donghu; Zhong;, Yanping; Li, Shunxing; Liu, Xin;; Laws, Edward A.; Huang, Bangqin (2021) Blackfordia virginica blooms shift the trophic structure to smaller size plankton in subtropical shallow waters, Marine Pollution Bulletin 182(111990): Published online

Jaspers, Cornelia; Bezio, Nicholas; Hinrichsen, Hans-Harald (2021) Diversity and physiological tolerance of native and invasive jellyfish/ctenophores along the extreme salinity gradient of the Baltic sea, Diversity 13(57): Published online

Johnson, William S.; Allen, Dennis M. (2005) <missing title>, Johns Hopkins Press, Baltimore. Pp. <missing location>

Kramp, P. L. (1961) Synopsis of the medusae of the world, Journal of the Marine Biological Association of the United Kingdom 40: 7-443

Leidy, R. A. (2007) Ecology, assemblage structure, distribution, and status of fishes in streams tributary to the San Francisco estuary, California, San Francisco Estuary Institute, Oakland CA. Pp. <missing location>

Light, Theo; Grosholtz, Ted; Moyle, Peter (2005) Delta ecological survey (phase1): Nonindigenous aquatic species in the Sacramento-San Joaquin Delta, a literature review, In: None(Eds.) None. , Stockton, CA. Pp. <missing location>

Llansó, Roberto J.; Sillett, Kristine (2009) <missing title>, Versar, Inc., Columbia MD. Pp. 1-34

Logvinenko, B. M. (1959) [On the occurence of the medusa Blackfordia virginica in the Caspian Sea.], Zoologicheskii Zhurnal 38(8): 1257-1258

Lopes, Evandro P. (2011) Leiosolenus aristatus (Dillwyn, 1817), new to the Cape Verde Islands (Mollusca, Bivalvia, Mytilidae), Zoologia Caboverdiana 2(2): 71-73

Madalena, Victoria Mariel Vidal; Dutto, María Sofía; Baranzano, Irene Machado (2021) First record of the non-native medusa Blackfordia virginica (Hydrozoa, Leptomedusae) on the coast of Uruguay, Southwestern Atlantic, Ocean and Coastal Research 60(e1030): Published online
http://doi.org/10.1590/2675-2824069.20013vmvm

Marques, F.; Chainho, P.; Costa, J. L.; Domingos, I.; Angelico, M. M. (2015) Abundance, seasonal patterns and diet of the non-native jellyfish Blackfordia virginica in a Portuguese estuary, Estuarine, Coastal and Shelf Science 167: 212-219

Marquez, Federico M.; Zabala, Soledad; Bokenhans, Verena; Cumplido, Mariano; Espinosa, Free; Bigatti, Gregorio; Averbuj, Andres (2024) Predation of the invasive green crab Carcinus maenas on the edible snail Buccinastrum deforme, targeted as the most important nearshore marine gastropod fishery from Patagonia, Argentina, Regional Studies in Marine Science 69(103299): Published online
https://doi.org/10.1016/j.rsma.2023.103299

Mayer, A. G. (1910) Medusae of the World., In: (Eds.) . , Washington, D.C.. Pp. 231, 276-278

Mills, C. E.; Sommer, F. (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, Claudia E. 1998 Acta Errata. <missing URL>



Mills, Claudia E.; Rees, John, T. (2000) New observations and corrections concerning the trio of invasive hydromedusae Maeotias marginata, Blackfordia virginica, and Moerisia sp. in the San Francisco estuary, Scientia Marina 64: 151-155

Mills, Claudia; Marques, Antonio; Migotto, Alvaro E; Calder, Dale R.; Hand, Cadet (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California Press, Berkeley CA. Pp. 118-168

Moore, S. J. (1987) Redescription of the leptomedusan Blackfordia virginica, Journal of the Marine Biological Association of the United Kingdom 67: 287-291

Mordukhai-Boltovskoi, Ph. D. (1964) Caspian fauna beyond the Caspian Sea, Internationale Revue der Gesamten Hydrobiologie 49(1): 139-170

Naumov, D. V. (1969) <missing title>, Israel Program for Scientific Translations, Jerusalem. Pp. <missing location>

Nogueira, Miodeli Jr.; De Oliveira, Juliana S. (2006) Moerisia inkermanica Paltschikowa-Ostroumova (Hydrozoa; Moerisidae) e Blackfordia virginica Mayer (Hydrozoa; Blackfordiidae) na Baía de Antonina, Paraná, Brasil., Pan-American Journal of Aquatic Sciences 1(1): 35-42

Ocaña-Luna, Alberto; Sánchez-Ramírez, Marina; Islas-García, Alejandro (2021) Temporal abundance and population parameters of the invasive medusa Blackfordia virginica Mayer, 1910 (Hydroidomedusae: Blackfordiidae) in Pueblo Viejo lagoon, Mexico, BioInvasions Records 10: Published onlibe

Oliveira, Otto M. P. and 24 authors (2016) Census of Cnidaria (Medusozoa) and Ctenophora from South American marine waters, Zootaxa 4194: 1-256

Patrick, Ruth (1994) Rivers of the United States, In: (Eds.) . , New York. Pp. <missing location>

Rees, John T.; Gershwin, Lisa-Ann (2000) Non-indigenous hydromedusae in California's upper San Francisco estuary: life cycle, distribution, and potential environmental impacts., Scientia Marina 64(Suppl. 1): 73-86

Richards, Horace Gardiner (1938) <missing title>, Bruce Humphries, Inc., Boston. Pp. <missing location>

Ruiz, G.M.; Fofonoff, P. W.; Carlton, J. T.; Wonham, M. J.; Hines, A. H. (2000) Invasion of coastal marine communities in North America: Apparent patterns, processes, and biases., Annual Review of Ecology and Systematics 31: 481-531

Schroeter, Robert E. (2008) Biology and long-term trends of alien hydromedusae and striped bass in a brackish tidal marsh in the San Francisco estuary, San Francisco Estuary and Watershed Science 13(Published onlin): 1-223

Shadrin, Nikolai 2000 List of exotic introduced species in the Black Sea. <missing URL>



Soors, Jan; Faasse, Marco; Stevens, Maarten; Verbessem, Ingrid; De Regge, Nico;Van den Bergh, Ericia (2010) New crustacean invaders in the Schelde estuary (Belgium), Belgian Journal of Zoology 140: 3-10

Thiel, Von Max Egon (1935) Zur kenntnis der hydromedusenfauna des Schwarzen Meeres, Zoologischer Anzeiger 111(7/8): 161-174

von Prahl , Henry; Manjarres, Gustavo (1984) Gecarcindae crabs (Crustacea: Gecarcidnidae) of Colombia, Cladasia 14(66): 156-166

Wintzer, Alpa P.; Meek, Mariah H.; Moyle, Peter B.; May, Bernie (2011a) Ecological insights into the polyp stage of non-native hydrozoans in the San Francisco Estuary, Aquatic Ecology 45: 151-161

Wintzer, Alpa P.; Meek, Mariah H.; Moyle, Peter B. (2013) Abundance, size, and diel feeding ecology of Blackfordia virginica (Mayer, 1910), a non-native hydrozoan in the lower Napa and Petaluma Rivers, California (USA), Aquatic Invasions 8: in press

Wonham, Marjorie J.; Carlton, James T. (2005) Trends in marine biological invasions at local and regional scales: the Northeast Pacific Ocean as a model system, Biological Invasions 7: 369-392

Young, Craig S; Gobler, Christopher J. (None) Coastal ocean acidification and nitrogen loading facilitate invasions of the non-indigenous red macroalga, Dasysiphonia japonica, Biological Invasions <missing volume>: 1367-1391(

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