Description
Maeotias marginata has a sexual medusa (well-known) and an asexual hydroid phase which has only been recently described (Mills and Rees 2000). The hydroid attributed to this species by Mills and Sommer (1995) actually was a Moerisia sp. The hydroid of M. marginata is 0.1 mm long, and difficult to distnguish from the detritus to which it adheres (Rees and Gershwin 2000).
Species Name- The earliest description of this animal was made by Modeer in 1791, based on specimens collected in the Netherlands. This Dutch population is apparently one of the earliest known marine invasions. The species name 'marginata' thus takes precedence over 'inexspectata' and 'inexpectata' used by Ostroumoff in 1896 (Mills and Rees 2000).
Order, Family- Mills and Sommer (1995) moved this hydrozoan to the order Anthomedusae, and family Moersiidae based on the apparent absence of statocysts (balance organs) on the margin of the medusa, and on the misidentification of the hydroid. Mills and Rees (2000) reexamined the medusae and found the statocysts. They advocated moving the species back to the order Limnomedusae, family Olindiidae (Kramp 1961; Naumov 1969), until its relationships can be determined more precisely.
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Cnidaria | Hydrozoa | Limnomedusae | Olindiidae | Maeotias |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1968 | Established | Unknown | Introduced | Regular Resident | Eastern Atlantic | Eastern Atlantic | Shipping(Ballast Water,Fouling Community) |
History of Spread
The hydrozoan Maeotias marginata is native to the Black Sea and 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) (Mills and Sommer 1995). Other widespread invaders of this fauna are Cordylophora caspia, Moerisia spp., Blackfordia virginica. The medusa of M. marginata was first discovered in canals in the Netherlands in the 18th century, and was present in the Netherlands in 1889. These occurrences apparently represent a very early introduction by shipping (Mills and Rees 2000). 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. The medusae was collected in the Loire estuary, France, in 1972 ( Denayer 1973), Chesapeake Bay in 1968 (Calder and Burrell 1969), the Edisto River, SC in 1972 (Burrell and Joseph 1974), and the Petaluma River, San Francisco Bay, in 1992 (Mills and Sommer 1993), and the Baltic Sea in Finland in 1990 (Leppakoski and Olenin 1999).
In the Chesapeake Bay, Maeotias marginata was collected from the Pamunkey River, VA, a York tributary in October and November of 1968, and September of 1970 (Calder and Burrell 1969; Calder 1972). We are aware of no later records of Maeotias marginata in the Chesapeake Bay, but this may reflect limited studies of hydromedusae since then. The hydroids are unlikely to be detected in the Chesapeake Bay without a specific sampling effort, owing to their small size (0.1 mm) and their occurrence on detritus (Rees and Gershwin 2000).
History Reference - Burrell and Joseph 1974; Calder 1971; Calder 1972; Calder and Burrell 1969; Denayer 1973; Leppakoski and Olenin 1999; Mills 1999; Mills and Rees 2000; Mills and Sommer 1993; Rees and Gershwin 2000
Invasion Comments
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | 11.3 | 27.0 | ||
| Salinity (‰) | 4.2 | 15.0 | ||
| Oxygen | ||||
| pH | ||||
| Salinity Range | oligo-poly |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 1.0 | 1.0 |
| Typical Adult Size (mm) | 23.0 | 23.0 |
| Maximum Adult Size (mm) | 45.0 | 45.0 |
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
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| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
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| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
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| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Maeotias marginata has no known economic impacts in the Chesapeake Bay region.
Economic Impacts Outside of Chesapeake Bay
Mills and Rees (2000) have suggested that Maeotias marginata predation could affect foodwebs and fisheries in low-salinity waters of San Francisco Bay. However, these impacts have not been studied there or elsewhere in this species' range.
References- Mills and Rees 2000
Ecological Impacts on Chesapeake Native Species
Maeotias marginata is apparently scarce in the Chesapeake Bay. Impacts on native biota have not been reported here or elsewhere in its range. However, Mills and Rees (2000) suggest that this hydrozoan could potentially alter planktonic foodwebs in low-salinity habitats of San Francisco Bay and other estuaries, including Chesapeake Bay, where no native medusae exist.
ompetition- In Suisun Marsh, San Francisco Bay, M. marginata medusae overlap with larvae of Morone saxatilis (Striped Bass), and could be competing with them for food . Potentially, M. marginata sp. is a potential 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).
References- Mills and Rees 2000
Ecological Impacts on Other Chesapeake Non-Native Species
Maeotias inexspectata is apparently scarce in the Chesapeake Bay. Impacts on exotic biota have not been reported here or elsewhere in its range.
References
Burrell, V. G.; Joseph, Jeanne, D. (1974) Occurrence of Maeotias inexpectata in South Carolina, Journal of the Elisha Mitchell Scientific Society 90: 51Calder, 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., Burrell, Victor G. (1967) Occurrence of Moerisia lyonsi (Limnomedusae, Moerisiidae) in North America, The American Midland Naturalist 78: 540-541
Calder, Dale R.; Burrell, Victor G. (1969) Brackish water hydromedusa Maeotias inexpectata in North America, Nature 222: 694-695
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
Kramp, P. L. (1961) Synopsis of the medusae of the world, Journal of the Marine Biological Association of the United Kingdom 40: 7-443
Leppakoski, Erkki; Olenin, Sergei (2000) Non-native species and rates of spread: lessons from the brackish Baltic Sea., Biological Invasions 2: 151-163
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: 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
1998 Acta Errata. http://faculty.washington.edu/cemills/ActaErrata.html
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
Naumov, D. V. (1969) Hydroids and Hydromedusae of the U.S.S.R., , Jerusalem. Pp.
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: 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: 1-223
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