Maeotias marginata

Invasion History

First Non-native North American Tidal Record: 1968
First Non-native West Coast Tidal Record: 1981
First Non-native East/Gulf Coast Tidal Record: 1968

---

General Invasion History:

The hydrozoan Maeotias marginata is native to the Black Sea and the Sea of Azov (Naumov 1969), and is considered to be part of the 'Sarmatic' cnidarian fauna (named for an ancient sea and an early tribe of the region) (Naumov 1969; Mills and Sommer 1995). Other widespread invaders of this fauna are Cordylophora caspia, Moerisia spp., and Blackfordia virginica. The medusa of M. marginata was first discovered in canals in the Netherlands in 1762 and again in 1889 (Mills and Rees 2000). These occurrences apparently represent a very early introduction by shipping. We do not know if M. marginata is still present in the Netherlands. In 1896, M. marginata (as M. inexspectata or M. inexpectata) was described from its native region, the Black Sea, by Ostroumoff (Naumov 1969).

Maeotias marginata became widely introduced in the 20th century. Medusae were collected in the Chesapeake Bay in 1968 (Calder and Burrell 1969); the Edisto River, South Carolina in 1972 (Burrell and Joseph 1974); Loire estuary, France in 1972 (Denayer 1973); the Suisun Marsh, San Francisco Bay in 1981 (Mills and Sommer 1995); Fujian, China (Xu et al. 1985); and the Baltic Sea, Finland in 1990 (Vainola and Oulasvirta 2002). The medusa is limited to brackish waters, ~4-15 PSU, but tolerances of the polyp are unknown (Mills and Sommer 1995; Rees and Gershwin 2000).

North American Invasion History:

Invasion History on the West Coast:

On the West Coast, Maeotias marginata has only been observed in brackish parts of the San Francisco Bay estuary system. Field notes of conservation agencies suggest that it may have been seen in Suisun Slough as early as 1959 (Rees and Gershwin 2000), but the first definitive collection of the medusa was in 1981, in Suisun Marsh (Schroeter 2008). In 1992, it was collected in the Petaluma River (Mills and Sommer 1995), and later in the Napa River (Mills and Rees 2000), the Suisun Slough, and near Chipps Island in Suisun Bay (Lia McLaughlin 2003, IEP newsletter http://www.water.ca.gov/iep/newsletters/2003/IEPNewsletter_fall2003_mar23.pdf). Analysis of plankton survey records indicates a trend of increasing abundance in Suisun Marsh from 1981 to 2005 (Schroeter 2008).

Invasion History on the East Coast:

Maeotias marginata was collected from the Pamunkey River, Virginia, a York River tributary of Chesapeake Bay, in October and November of 1968, and September of 1970 (Calder and Burrell 1969; Calder 1972). We are not aware of later records of Maeotias marginata in the Chesapeake Bay, but this may reflect limited studies of hydromedusae since then. In 1972, Maeotias marginata was collected at the junction of Intracoastal Waterway and South Edisto River (Burrell and Joseph 1974). Again, we do not know of more recent records here or elsewhere on the East Coast. However, the hydroids are unlikely to be detected without a specific sampling effort, owing to their small size (0.1 mm) and their occurrence on detritus (Rees and Gershwin 2000).

Invasion History Elsewhere in the World:

As noted above, the medusa of M. marginata was first discovered in canals in the Netherlands in the 18th century, and was recorded again in 1889 (Mills and Rees 2000). This medusa tolerates freshwater for several days, which may aid in its invasion of canal systems (Mills and Rees 2000). Later appearances of this species are very spotty. One medusa was captured in the Loire estuary, France in 1971 (Denayer 1973). In 1999, numerous medusae were seen in the Väinameri region of the Estonian Baltic (Väinölä and Oulasvirta 2002). This medusa has also been reported from China, in the Jiulong River Estuary, near Xiamen (Xu et al. 1985). The spotty appearance of medusae may reflect very sporadic production by the very small and inconspicuous polyps, as in the related Craspedacusta sowerbii (Freshwater Jellyfish) (Acker and Muscat 1976).

---

Description

The hydroid stage of Maeotias marginata is very small (~0.1 mm height), lacks tentacles, and develops directly from eggs. The hydranth bears large transparent nematocysts oriented around the presumed mouth. The hydroids have been observed only in culture, and have not been detected in the field (Rees and Gershwin 2000; Wintzer et al. 2011a). Hydroids in a culture dish adhered to detritus and other hydroids, not to the glass of the dish. The hydroid illustrated as M. inexspectata (=marginata) in Mills and Sommer (1995) actually belongs to Moerisia sp. (Mills and Rees 2000; Rees and Gershwin 2000).

The medusae have a roughly hemispherical umbrella, with four radial canals. They are released at about 1 mm in diameter, and initially have four tentacles and radial canals, as well as a well-developed ring canal. Mature medusae have the four radial canals but develop up to 60 smaller centripetal canals per quadrant, and over 500-600 tentacles. Each tentacle arises from a bulb with a deep reddish-brown ocellus. As the medusa matures, it acquires statocysts, arranged in three rows along the umbrella margin. The medusae grow up to 50 mm diameter and ~25-30 mm high. The umbrella is clear in younger medusae, but opaquely white, with pinkish or brownish color around the rim of the bell in adults. The manubrium reaches almost to the mouth of the bell, and has its margins elongated into four frilly lips. The four main radial canals are draped with hanging folds of gonads. When extended, the tentacles exceed the diameter of the bell. (Description from: Naumov 1969; Denayer 1973; Mills and Sommer 1995; Mills and Rees 2000; Rees and Gershwin 2000; Bouillon et al. 2004)

---

Taxonomy

Ecology

General:

Maeotias marginata has a conspicuous planktonic medusa stage, and a small obscure hydroid stage. Hydroids have only been described from San Francisco Bay, in culture (Mills and Rees 2000), and have not been studied in the field. The hydroids were attached to bits of detritus in the bottom of culture dishes, but did not attach to the glass. Feeding was not observed, and polyps did not grow in culture (Rees and Gershwin 2000). Presumably, benthic or zooplankton prey would be stung and captured by nematocysts near the mouth and ingested. Polyps are presumed to bud asexually to produce new polyps, and also to bud off medusae, but these processes have not yet been described.

Medusae appear in the plankton at about 1mm in diameter, and feed on zooplankton, including barnacle larvae, copepods, crab zoeae, copepod eggs, and tanaids (Mills and Sommer 1995; Schroeter 2008). In the San Francisco estuary, the medusae fed primarily on calanoid copepods (65%), barnacle nauplii (14%), cyclopoid copepods (14%), and corophiid amphipods (4%) (Wintzer et al. 2011c). The medusae appear to be heavier than water, and remain close to the bottom, with occasional bouts of upward swimming (Mills and Sommer 1995). In the field, they pulse to the surface, flip over, and slowly sink, with extended tentacles (Rees and Gershwin 2000). Medusae in Mills and Sommer's (1995) San Francisco estuary study were all male, but in 1996, Rees and Gershwin (2000) collected some females, and were able to observe the development of fertilized eggs, which metamorphosed directly into small polyps (Rees and Gershwin 2000). Many aspects of the life cycle remain poorly understood.

Food:

Copepods, barnacle nauplii, crab zoeae

Trophic Status:

Carnivore

Carn

---

Habitats

General Habitat	Unstructured Bottom	None
General Habitat	Grass Bed	None
Salinity Range	Mesohaline	5-18 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None
Vertical Habitat	Planktonic	None

---

---

Tolerances and Life History Parameters

Maximum Temperature (ºC)	27	Field, Suisun Marsh (Schroeter 2008)
Minimum Salinity (‰)	0.9	Field observations of medusae (Mills and Sommer 1995; Schroeter 2008), but up to 10 days of survival of medusae in fresh water. (Mills and Rees 2000) Salinity tolerance of polyps is unknown.
Maximum Salinity (‰)	15	Experimental observations of medusae (Mills and Sommer 1995), (Mills and Rees 2000) Salinity tolerance of polyps is unknown.
Minimum Dissolved Oxygen (mg/l)	2.8	Field, Suisun Marsh (Schroeter 2008)
Minimum Reproductive Temperature	11.3	Field Temperatures for medusae (Calder and Burrell 1969; Denayer 1973; Mills and Sommer 1995)
Maximum Reproductive Temperature	27	Field Temperatures for medusae (Calder and Burrell 1969; Denayer 1973; Mills and Sommer 1995)
Maximum Width (mm)	50	Medusa width (Naumov 1969; Mills and Sommer 1995; Mills and Rees 2000)
Broad Temperature Range	None	Cold temperate-Warm temperate
Broad Salinity Range	None	Mesohaline

General Impacts

Maeotias marginata, together with other introduced hydrozoans in brackish estuaries (Moerisia spp., Cordylophora caspia, Blackfordia virginica), has the potential to alter planktonic food webs through predation on zooplankton. Most estuaries have few or no native brackish-water hydrozoans (Calder 1972; Calder 1976; Rees and Gershwin 2009).

Ecological Impacts

Competition- In Suisun Marsh, M. marginata medusae overlap with larvae of Morone saxatilis (Striped Bass) and could be competing with them for food. Maeotias marginata is a possible competitor with larval fishes, particularly economically important Striped Bass (Morone saxatilis) and endangered Delta Smelt (Hypomesus transpacificus) (Schroeter 2008; Wintzer et al. 2011b; Wintzer et al. 2011c). Temporal and dietary overlap was greatest with Delta Smelt, and introduced Threadfin Shad (Dorosoma petenense), but minimal with Morone saxatilis and threatened Longfin Smelt (Spirinchus thaleichthys) (Wintzer et al. 2011c). Predation on fish larvae occurred, but at a very low rate, less than 1% of food contents (Schroeter 2008; Wintzer et al. 2011c).

---

Regional Impacts

P090	San Francisco Bay		Ecological Impact	Competition
Potentially, M. marginata sp. is a competitor with larval fishes, particularly economically important Striped Bass (Morone saxatilis) and endangered Delta Smelt (Hypomesus transpacificus) (Schroeter 2008; Wintzer et al. 2011b; Wintzer et al. 2011c). Temporal and dietary overlap was greatest with Delta Smelt, and introduced Threadfin Shad (Dorosoma petenense), but minimal with Morone saxatilis and threatened Longfin Smelt (Spirinchus thaleichthys) (Wintzer et al. 2011c).
NEP-V	Northern California to Mid Channel Islands		Ecological Impact	Competition
Potentially, M. marginata sp. is a competitor with larval fishes, particularly economically important Striped Bass (Morone saxatilis) and endangered Delta Smelt (Hypomesus transpacificus) (Schroeter 2008; Wintzer et al. 2011b; Wintzer et al. 2011c). Temporal and dietary overlap was greatest with Delta Smelt, and introduced Threadfin Shad (Dorosoma petenense), but minimal with Morone saxatilis and threatened Longfin Smelt (Spirinchus thaleichthys) (Wintzer et al. 2011c).
CA	California		Ecological Impact	Competition
Potentially, M. marginata sp. is a competitor with larval fishes, particularly economically important Striped Bass (Morone saxatilis) and endangered Delta Smelt (Hypomesus transpacificus) (Schroeter 2008; Wintzer et al. 2011b; Wintzer et al. 2011c). Temporal and dietary overlap was greatest with Delta Smelt, and introduced Threadfin Shad (Dorosoma petenense), but minimal with Morone saxatilis and threatened Longfin Smelt (Spirinchus thaleichthys) (Wintzer et al. 2011c)., Potentially, M. marginata sp. is a competitor with larval fishes, particularly economically important Striped Bass (Morone saxatilis) and endangered Delta Smelt (Hypomesus transpacificus) (Schroeter 2008; Wintzer et al. 2011b; Wintzer et al. 2011c). Temporal and dietary overlap was greatest with Delta Smelt, and introduced Threadfin Shad (Dorosoma petenense), but minimal with Morone saxatilis and threatened Longfin Smelt (Spirinchus thaleichthys) (Wintzer et al. 2011c).

References

Acker, Thomas; Muscat, Anne M. (1976) The ecology of Craspedacusta sowerbii Lankester, a freshwater hydrozoan, American Midland Naturalist 95(2): 323-336

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



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

Burrell, V. G.; Joseph, Jeanne, D. (1974) Occurrence of Maeotias inexpectata in South Carolina, Journal of the Elisha Mitchell Scientific Society 90(1): 51

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. (1976) The zonation of hydroids along salinity gradients in South Carolina estuaries, In: (Eds.) Coelenterate Ecology and Behavior. , New York. Pp. 165-174

Calder, Dale R.; Burrell, Victor G. (1969) Brackish water hydromedusa Maeotias inexpectata in North America, Nature 222: 694-695

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>

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

Gershwin, Lisa-Ann (2001) Systematics and biogeography of the jellyfish, Aurelia labiata (Cnidaria: Scyphozoa), Biological Bulletin 201: 104-119

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>

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

Meek, Mariah H.; Baerwald, Melinda R.; Wintzer, Alpa P.; May, Bernie (2009) Isolation and characterization of microsatellite loci in two non-native hydromedusae in the San Francisco Estuary: Maeotias marginata and Moerisia sp., Conservation Genetics Resources 1: 205-208

Meek, Mariah H.; Wintzer, Alpa P.; Shepherd, Nicole; May, Bernie (2012) Genetic diversity and reproductive mode in two non-native hydromedusae, Maeotias marginata and Moerisia sp., in the upper San Francisco Estuary, California, Biological Invasions 15(1): 199-212

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. (2001) Jellyfish blooms: are populations increasing globally in response to changing ocean conditions?, Hydrobiologia 451: 55-68

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

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

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

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

Vainola, Risto; Oulasvirta, Panu (2002) The first record of Maeotias marginata (Cnidaria, Hydrozoa) from the Baltic Sea., Sarsia 86: 401-404

Von Numers, Mikael (2013) The first record of Maeotias marginata (Modeer, 1791) (Cnidaria, Hydrozoa) from Finland, northern Baltic Sea, Bioinvasions Records 2: in press

Wintzer, Alpa P.; Meek, Mariah H.; Moyle, Peter B. (2011c) Trophic ecology of two non-native hydrozoan medusae in the upper San Francisco estuary, Marine and Freshwater Research 62: 952-961

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. (2011b) Life history and population dynamics of Moerisia sp., a non-native hydrozoan in the upper San Francisco Estuary (U.S.A.), Estuarine, Coastal and Shelf Science 54: 48-55

Xu, Zhenzu; Huang, Jiaqi; Wang, Wenqiao,. (1985) On new species and records of hydromedusae from the Jiulong River estuary of Fujian, China, Journal of Xiamen University Natural Science 24: 102-110

---