Zebra mussel

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Zebra mussel

Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Subclass:	Heterodonta
Order:	Veneroida
Superfamily:	Dreissenoidea
Family:	Dreissenidae
Genus:	Dreissena
Species:	D. polymorpha

Binomial name

Dreissena polymorpha
Pallas, 1771

The Zebra mussel, Dreissena polymorpha, is a bivalve mussel native to freshwater lakes of southeast Russia. Zebra mussels get their name from the striped pattern on their shells, though not all shells bear this pattern. They are usually about the size of a fingernail, but can grow to a maximum length of nearly two inches. [1]

Its native distribution is Black and Caspian Sea. Zebra mussels are considered an invasive species in North America, in Spain and in Sweden.

1 Reproduction
2 Spread
3 Ecology
4 Anatomy
5 Predators of zebra mussels
6 Effects of zebra mussels
7 References
8 External links

[edit] Reproduction

An adult female zebra mussel is one of the most reproductive organisms in the world. It may produce between 30,000 and 1 million^[1] eggs per year. Spawning usually begins in the months from late spring to early summer by free-swimming larvae (veligers).

[edit] Spread

Zebra mussel was found and described first in part of Russia, but then it was recognized in the Caspian Sea. Grossinger reported it in Hungary in 1794. Kerney and Morton described the rapid colonization of Britain by the zebra mussel, first in Cambridgeshire in the 1820's, London in 1824, and in the Union Canal near Edinburgh in 1834. ^[2] In 1827 zebra mussels were seen in the Netherlands at Rotterdam. Canals that artificially link many European waterways facilitated their early dispersal. It was recorded in Bohemia in Elbe river (now in The Czech Republic) in 1893^[3]. Around 1920 the mussels reached lake Mälaren in Sweden.

Sign advising boaters on how to prevent zebra mussel spread on Titicus Reservoir in North Salem, New York.

The first Italian appearance of the organism was in northern Italy in Lake Garda in 1973^[4]; in central Italy they have appeared in Tuscany since 2003^[5].

In the U.S., they were first detected in the Great Lakes in 1988, in Lake St. Clair, located between Detroit, Michigan and Windsor, Ontario. It is believed they were inadvertently introduced into the lakes in the ballast water of ocean-going ships traversing the St. Lawrence Seaway. Another possible often neglected mode of introduction is on anchors and chains, although this has not been proven. Since adult zebra mussels can survive out of water for several days or weeks if temperature is low and humidity is high, chain lockers provide temporary refuge for clusters of adult mussels that could easily be released when transoceanic ships drop anchor in freshwater ports.

From their first appearance in American waters in 1988 zebra mussels have spread to a large number of waterways, including the Mississippi, Hudson, St. Lawrence, Ohio, Cumberland, Missouri, Tennessee, Colorado, and Arkansas rivers disrupting the ecosystems, killing the local unionid mussels, (primarily by out-competing native species for food)^{[citation needed]} and damaging harbors, boats, and power plants. Water treatment plants were initially hit hardest because the water intakes brought the microscopic free-swimming larvae directly into the facilities. The U.S. Coast Guard estimates that economic losses and control efforts cost the United States about $5 billion each year.

A common inference made by scientists predicts that the zebra mussel will continue spreading passively, by ship and by pleasure craft, to more rivers in North America. Trailered boat traffic is the most likely vector for invasion into the North American west. This spread is preventable if boaters would take time to thoroughly clean and dry their boats and associated equipment before transporting these to new water bodies. Since no North American predator or combination of predators has been shown to significantly reduce zebra mussel numbers,^{[citation needed]} such spread would most likely result in permanent establishment of zebra mussels in many North American waterways.

[edit] Ecology

Zebra Mussel

Zebra mussels and the closely related and ecologically similar quagga mussel are voracious filter-feeding organisms. They remove particles from the water column, increasing water clarity and reducing pollution. Some particles are consumed as food, and feces are deposited on the lake floor. Non-food particles are combined with mucus and other matter and deposited on lake floors as pseudofeces.

Lake floor food supplies are enriched by zebra mussels as they filter pollution out of the water. This biomass becomes available to bottom feeding species and to the fish that feed on them. The zebra mussel reduced eutrophication of Lake Erie^[6] and increased water quality.^[7] The catch of yellow perch increased 5 fold after the introduction of zebra mussels into Lake St. Claire.^[8] Zebra mussels attach to most substrates including sand, silt, and harder substrates. Other mussel species frequently represent the most stable objects in silty substrates, and zebra mussels attach to, and often kill these mussels.^{[citation needed]} This has eliminated many native mussel species from affected lakes in North America.^{[citation needed]} This pattern is being repeated in Ireland where zebra mussels have eliminated the two freshwater mussels from several waterways, including some lakes along the Shannon.^{[citation needed]}

[edit] Anatomy

Zebra mussels are relatively small in size, adults range from 1/4 to 1 1/2 inches long[2]. They have tiny stripes down their shells, hence the name Zebra Mussels. Zebra Mussels have a D-shaped shell. They attach to things with strings coming out of their umbo on the dorsal surface (side with the hinge). These strings are called byssal threads and make it very hard to remove the zebra mussel from the area it is attached to.

[edit] Predators of zebra mussels

There are a number of natural predators of zebra mussel. Zebra mussels have high nutritional value (Walz, 1979) and are consumed in large quantities by crayfish, waterfowl and in smaller quantities by muskrats. The nutritional value changes seasonally, particularly in terms of protein and carbonate content.

Crayfish could have a significant impact on the densities of 1 to 5 mm long zebra mussels. An adult crayfish consumes an average of nearly 105 zebra mussels everyday, or in all about 6000 mussels in a season. Predation rates are significantly reduced at cooler water temperatures.

Several species of fish consume zebra mussels. Of these, roach seems to have the most significant impact on mussel densities. In some Polish lakes the diet of the roach consists almost exclusively (~95%) of zebra mussels (Stanczykowska, 1957). Despite all this, it seems that fish do not limit the densities of zebra mussels in European lakes. Mackie et al 1989

[edit] Effects of zebra mussels

Zebra mussel infestation on the walls of Arthur V. Ormond Lock on the Arkansas River

Zebra mussel-encrusted Vector Averaging Current Meter from Lake Michigan

Zebra mussels are filter feeders. When in the water, they open their shells to admit detritus.

Zebra mussels are a great nuisance to people. Since colonizing the Great Lakes, they have covered the undersides of docks, boats, and anchors. They have also spread into streams and rivers nationwide. In some areas they completely cover the substrate, sometimes covering other freshwater mussels. They can grow so densely that they block pipelines, clogging water intakes of municipal water supplies and hydroelectric companies.

Zebra mussels and other non-native species are credited with the increased population and size of smallmouth bass in Lake Erie. [3] Zebra mussels are also believed to be the source of deadly avian botulism poisoning that has killed tens of thousands of birds in the Great Lakes since the late 1990s. [4] They also cleanse the waters of inland lakes, resulting in increased sunlight penetration and growth of native algae at greater depths. This proves beneficial for fish most of the time, helping the fish live in better conditions.

[edit] References

^ /nationalatlas.gov
^ Mackie, G; Gibbons, W; Muncaster, B & Gray, I, The Zebra Mussel, Dreissena polymorpha: A synthesis of European Experiences and a preview for North America, Ontario Ministry of Environment
^ Blažka, F. (1893). "Do Čech zavlečená slávka: Dreissena polymorpha Pall." (in Czech). Vesmír 22 (15): 177-178.
^ Giusti F and Oppi E (1973). "Dreissena polymorpha (Pallas) nuovamente in Italia. (Bivalvia, Dreissenidae)" (in Italian). Mem Mus Civ St Nat Verona 20: 45-49.
^ Elisabetta Lori and Simone Cianfanelli (2006). "New records of Dreissena polymorpha (Pallas, 1771) (Mollusca: Bivalvia: Dreissenidae) from Central Italy" (in English). Aquatic Invasions 1 (4): 281-283.
^ Holland, R. E.; Johengen, T. H. & Beeton, A. M., Trends in nutrient concentrations in Hatchery Bay, western Lake Erie, before and after Dreissena polymorpha., vol. 52:1202-1209, Canadian Journal of Fisheries and Aquatic Sciences
^ Garton, D. W.; Berg, D. J.; Stoeckmann, A. M. & Hagg, W. R., Biology of recent invertebrate invading species in the Great Lakes: The spiny water flea, Bythotrephes cederstoemi, and the zebra mussel, Dreissena polymorpha. pages 63-84 (in B. N. McKnight editor. Biological pollution: The control and impact of invasive exotic species. ed.), Indianapolis, Indiana.: Indiana Academy of Science.
^ Saggoff, M., What’s Wrong with Exotic Species?, College Park, Maryland: Institute for Philosophy and Public Policy, Maryland School of Public Affairs, <http://www.puaf.umd.edu/IPPP/fall1999/exotic_species.htm>