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Overview
Short description of Mnemiopsis leidyi, American comb jelly
A comb jelly up to 180 mm in length, usually transparent or slightly milky and translucent with four rows of small ciliated combs which are iridescent by day and may glow green by night. A key distinguishing feature is the presence of oral lobes which span nearly the entire length of the body.
Description of Mnemiopsis leidyi, American comb jelly status in GB
The sea walnut was recorded in the Ouse Esturay in 2016 and has been recorded from the North Sea off the Netherlands coast since 2006.
Habitat summary: Mnemiopsis leidyi, American comb jelly
It occurs in the water column of shallow estuaries, bays and coastal waters, tolerating temperatures of 0-32 °C and salinities from <two – 38 psu.
Overview table
| Environment: |
Marine
|
| Species status: |
Non-Native
|
| Native range: |
Northeastern U.S.A.
|
| Functional type: |
Predator
|
| Status in England: |
Non-Native
|
| Status in Scotland: |
Non-Native
|
| Status in Wales: |
Non-Native
|
| Location of first record: |
Ouse estuary
|
| Date of first record: |
2016
|
Invasion history: Mnemiopsis leidyi, American comb jelly
Origin
The sea walnut is thought to be native to estuaries along the Atlantic coasts of North and South America, occupying coastal waters over a wide latitudinal range (40° N to 46° S) from Massachusetts to southern Argentina.
First Record
First record Ouse Esturay in 2016. In Europe it was first recorded in the Black Sea during the early 1980s.
Pathway and Method
The sea walnut is thought to have been transported to the Black Sea within the ballast water of cargo ships. Oliveira (2007) suggests that this species may be capable of long range dispersal through transoceanic drifting. It is possible that the arrival of this species in GB waters in 2016 was as secondary spread on natural currents from the previously invaded range.
Species Status
Following its accidental introduction with ballast water into the Black Sea during the early 1980s, the sea walnut spread into adjacent waters of the Mediterranean, Azov, Aegean, Marmara and Caspian Seas. It invaded almost the entire Caspian Sea within a year. In 2006 it was recorded from the Baltic Sea and Danish waters. In 2007 very high densities were found in a shallow Danish fjord system (up to 800 individuals m-3). The first occurrences in the North Sea were noted in 2006, near Helgoland and off the western coast of the Netherlands. During summer 2009 there were several records from the NW Mediterranean coast of Spain as well as Mediterranean coasts of Italy and Israel. In 2016 the first record was received from GB waters - the Ouse Estuary.
Ecology & Habitat: Mnemiopsis leidyi, American comb jelly
Dispersal Mechanisms
The sea walnut is planktonic through all stages of the life cycle and is dispersed by water currents.
Reproduction
This sea walnut is a simultaneous hermaphrodite capable of self-fertilization; viable offspring can be produced from a single adult. An individual first sheds sperm, then briefly disperses them and releases egg cells into its own sperm. Reproduction appears to depend on temperature and prey availability, different authors report varying minimum temperatures required for reproduction to occur. Fecundity (number of eggs produced) is related to body size, with larger individuals producing up to 8000 eggs. It is also able to regenerate from fragments larger than one quarter of an individual.
Known Predators/Herbivores
Comb jellies of the genus Beroe are known to feed selectively on other ctenophores with which they co-evolved. In its native habitat B. ovate is the major predator of the sea walnut, and following its unintentional introduction into the Black Sea, the sea walnut decreased by a factor of ten. B. cucumis may be a predator in GB waters. Numerous fish species, turtles, cetaceans and other jellies also prey upon comb jellies.
Resistant Stages
None known.
Habitat Occupied in GB
Ouse Estuary constitutes first record in 2016. It is known to occur in the water column of shallow estuaries, bays and coastal waters.
Distribution: Mnemiopsis leidyi, American comb jelly
Native range along the Atlantic coast of North and South America, from Massachusetts to southern Argentina. Not recorded from GB but recently recorded from the North Sea off the Netherlands coast.
Impacts: Mnemiopsis leidyi, American comb jelly
Environmental Impact
The sea walnut is a major predator of zooplankton, fish eggs and larvae. Following its introduction into the Black Sea a dramatic decrease in abundance of almost all prey species of pelagic fish and the disappearance of some zooplankton species was observed. Similar impacts occurred in the Caspian Sea, where effects were seen at all trophic levels including the top predator, the Caspian Seal. These extreme impacts occurred in the absence of natural predators; when a predator of the sea walnut was also unintentionally introduced to the Black Sea, M. leidyi numbers decreased rapidly and the ecosystem began to recover.
Health and Scoial Impact
None known.
Economic Impact
Collapse of fish stocks in the Black Sea has been partly attributed to predation of the sea walnut on fish eggs and larvae, and competition for zooplankton prey. The catch of sprat, anchovy and horse mackerel in the Black Sea in 1991 was less than one-fifth of that in 1988. Losses in the anchovy fishery were estimated at hundreds of millions of US dollars.
References & Links: Mnemiopsis leidyi, American comb jelly
Identification
Fuentes, V.L., Angel, D.L., Bayha, K.M., Atienza, D., Edelist, D., Bordehore, C., Gili, J-M. & Purcell, J.E. (2010) Blooms of the invasive ctenophore, Mnemiopsis leidyi, span the Mediterranean Sea in 2009. Hydrobiologia, 645, (1), 23-37.
Shiganova, T.A. & Panov, V. (2006) Delivering Alien Invasive Species Inventories for Europe: Mnemiopsis leidyi. [online] Available from: http:www.europe-aliens.orgpdfMnemiopsis_leidyi.pdf
Biology, ecology, spread, vectors
Finenko, G.A., Kideys, A.E., Anninsky, B.E., Shiganova, T.A., Roohi, A., Tabari, M.R., Rostami, H. & Bagheri, S. (2006) Invasive ctenophore Mnemiopsis leidyi in the Caspian Sea: feeding, respiration, reproduction and predatory impact on the zooplankton community. Marine Ecology Progress Series, 314, 171-185.
GESAMP. (1997) Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection. Opportunistic settlers and the problem of the ctenophore Mnemiopsis leidyi invasion in the Black Sea. GESAMP reports and studies 58, International Maritime Organisation, London.
Management and impact
Shiganova, T.A., Mirzoyan, Z.A., Studenikina, E.A., Volovik, S.P., Siokou-Frangou, I., Zervoudaki, S., Christou, E.D., Skirta, A.Y. & Dumont, H.J. (2001) Population development of the invader ctenophore Mnemiopsis leidyi, in the Black Sea and in other seas of the Mediterranean basin. Marine Biology, 139, 431-445.
General
Faasse, M.A. & Bayha, K.M. (2006) The ctenophore Mnemiopsis leidyi A.Agassiz 1865 in coastal waters of the Netherlands: an unrecognized invasion? Aquatic Invasions, 1, (4), 270-277.
Fuentes, V.L., Atienza, D., Gili, J-M. & Purcell, J.E. (2009) First records of Mnemiopsis leidyi A.Agassiz 1865 off the NW Mediterranean coast of Spain. Aquatic Invasions, 4, (4), Short communication.
https://www.cabi.org/isc/datasheet/75102
Gallery: American comb jelly
