''Maeotias'' is a genus of

hydrozoans Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Olindiidae Olindiidae is a family of hydrozoans in the order Limnomedusae. They have a polyp (zoology), polyp phase and a Jellyfish, medusa phase. The polyps are generally small (1 mm) and solitary, but a few species are colonial. They have a varying ...

. It is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus with only a single species, ''Maeotias marginata'', commonly known as the Black Sea jellyfish or brackish water hydromedusa and often referred to as ''Maeotias inexpectata'' in the literature. It was first described from the

Don Don, don or DON and variants may refer to: Places *County Donegal, Ireland, Chapman code DON *Don (river), a river in European Russia *Don River (disambiguation), several other rivers with the name *Don, Benin, a town in Benin *Don, Dang, a vill ...

and

Kuban Kuban (Russian language, Russian and Ukrainian language, Ukrainian: Кубань; ady, Пшызэ) is a historical and geographical region of Southern Russia surrounding the Kuban River, on the Black Sea between the Pontic–Caspian steppe, ...

estuaries of the

Sea of Azov The Sea of Azov ( Crimean Tatar: ''Azaq deñizi''; russian: Азовское море, Azovskoye more; uk, Азовське море, Azovs'ke more) is a sea in Eastern Europe connected to the Black Sea by the narrow (about ) Strait of Kerch, ...

(which was called the Lake of Maeotis in antiquity), and also occurs in the

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Roma ...

, all of which are areas of low

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

. It has been recorded in several other estuarine locations around the world and is regarded as an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

Description

''M. marginata'' has a small medusa with a bell diameter of up to . It is hemispherical in shape and the gonads hang from the four distinctive radial canals. The marginal ring canal has 50 short centripetal canals branching from it with a dense marginal fringe of about 600 short trailing tentacles. This hydrozoan is opaque white with a slightly reddish tinge near the bell margin.

Distribution

''Maeotias marginata'' is native to the Sea of Azov and the Black Sea. It has spread to other parts of the world and was first detected in North America in 1968 in the estuaries of rivers entering

Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic (United States), Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the ...

. It is thought to have been brought to America by shipping. The polyp stage possibly arrived as a

fouling Fouling is the accumulation of unwanted material on solid surfaces. The fouling materials can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Fouling is usually distinguished from other surf ...

organism on the hull of a ship but it is unlikely that a

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estua ...

species would have survived such a long voyage through saline ocean water. Alternatively, it may have arrived as an

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

or as an encysted dormant stage of a polyp. More likely, perhaps, it arrived in a

ballast tank A ballast tank is a compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide hydrostatic stability for a vessel, to reduce or control buoyancy, as in a submarine, to correct trim or list, ...

or in the

bilge water The bilge of a ship or boat is the part of the hull that would rest on the ground if the vessel were unsupported by water. The "turn of the bilge" is the transition from the bottom of a hull to the sides of a hull. Internally, the bilges (us ...

in a vessel. In 1999, it was observed in the northern Baltic Sea, and specimens have also been found in the Netherlands (1962), France (1971) and the Pacific coast of North America, where it was found in the estuaries of the

Petaluma Petaluma (Miwok: ''Péta Lúuma'') is a city in Sonoma County, California, located in the North Bay region of the San Francisco Bay Area. Its population was 59,776 according to the 2020 census. Petaluma's name comes from the Miwok village nam ...

and

Napa River The Napa River is a river approximately long in the U.S. state of California. It drains a famous wine-growing region called the Napa Valley, in the mountains north of the San Francisco Bay. Milliken Creek and Mt. Veeder watersheds are a few of ...

s flowing into

San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...

in 1992 and 1993, and has since become established.

Biology

The feeding behaviour of ''M. marginata'' has been observed in a shallow-water location with

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...

es growing in sand. It uses rhythmic contractions of the bell to move upwards through the water, then it flattens the bell and extends its tentacles widely and drifts slowly downwards, finally resting on the bottom in the same extended position for a while. During this descent, it captures and feeds on the

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

it encounters and small

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

organisms may be caught underneath as it lands. Its diet consists mostly of small

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s, including

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...

larvae,

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

eggs and larvae, and

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

larvae. ''M. marginata'' can reproduce both sexually and asexually, by budding. All individuals found in the Napa and Petaluma River population are male, and must have been produced asexually following the original introduction of perhaps a single male polyp.

References

{{Taxonbar, from=Q30075003, from2=Q2233476 Olindiidae Hydrozoan genera