Taxonomic name: Dreissena polymorpha (Pallas, 1771)
Synonyms: Mytilus polymorpha Pallas 1771
Common names: moule zebra (French), racicznica zmienna (Poland), zebra mussel (English), Zebra-Muschel (German)
Organism type: mollusc Zebra mussels (Dreissena polymorpha) are native to the Caspian and Black Seas. They are now established in the UK, Western Europe, Canada and the USA. They compete with zooplankton for food, thus affecting natural food webs. They also interfere with the ecological functions of native molluscs and cause great economic damage. Description
Black or brown and white striped bivalve mollusc with byssal attachment to hard substrates. Maximum size approx. 3cm long. Shell is highly carinate, having an angle between the ventral and dorsal surfaces. Colour patterns highly polymorphic, from almost pure black to unpigmented, with a variety of striped forms. Occurs in:
estuarine habitats, lakes, urban areas, water courses Habitat description
Tolerates salinity to 6ppt, temperatures to approx. 29 degrees C, will not settle in currents greater than 2m/sec. General impacts
Zebra mussels filter organic and inorganic particles between 7 and 400 microns, competing with native planktivores for food. The net result is a sedimentation of previously suspended organic matter in the form of feces and pseudofeces, shifting energy and nutrient balances from the pelagic to the benthic zone. Increases in water clarity favour increased photosynthesis by rooted aquatic macrophytes, and negatively effect fish species that prefer slightly turbid conditions, such as walleye. Removal of green algae gives cyanobacteria a competitive advantage, as zebra mussels will stop filtering in the presence of cyanobacteria. Zebra mussels settle in high numbers on native mussels (Unionidaceae), causing suffocation, starvation, and energetic stress leading to death. Loss of native mussel populations has increased dramatically where zebra mussels are present, particularly in the Great Lakes and Hudson and Mississippi rivers. Dense colonization of hard substrates is beneficial to benthic invertebrates, as habitat complexity increases as does availability of organic matter. Spawning reefs of fishes such as lake trout are negatively affected by zebra mussel colonies.Conroy et al. (2005) whilst discussing implications for Lake Erie ecosystem change state that: "Dreissenid mussels represent a dynamic link between the benthic and pelagic regions of a lake ecosystem (Ackerman et al. 2001)". (the benthic zone is the lowest level of all aquatic biomes. It includes the sea floor and bottom-dwelling organisms, pelagic refers to living in the water of the ocean above the bottom)
The authors observe that dreissenid mussels are both a sink and source of nutrients through consumption and excretion processes, respectively and thus have an impact on the nutrient regime of the Lake. Notes
Tolerates salinity to 6 ppt, temperatures to approx. 29 C, will not settle in currents greater than 2m/sec. Geographical range
Native range: Native range includes the Black, Caspian, and Azov seas;
Known introduced range: Since the 1700's its range has expanded westward to most of western Europe, UK, and North America, where it is found in the Great Lakes and all of the major river drainages east of the Rocky Mountains. Introduction pathways to new locations
Floating vegetation/debris:
Pet/aquarium trade: Possibly via aquarium dumping.
Ship:
Ship ballast water: Introduced between continents and among Great Lakes in ballast water.
Ship/boat hull fouling: Introduced to smaller lakes by overland transport on boat hulls and trailers.
Translocation of machinery/equipment:
Local dispersal methods
Aquaculture (local): Larvae may be transported during fish stocking.
Boat: Adults may attach to anchors and boat hulls and be transported.
On animals: Ducks could theoretically transport larvae in wet feathers.
Other (local): Larvae may be transported on scuba diver's wetsuits, or in scientific sampling equipment.
Water currents: Range expansion within North America has been very rapid due to downstream transport of planktonic larvae. Management information
Numerous control methods are available to remove mussels from substrates or kill them within infested water intakes or on fouled man-made substrates; none of these methods is useful for control in the wild. Controls include mechanical removal (scraping, mechanical scrubbers in pipes), chemical (chlorine, bromine, deoxygenation), thermal, UV light, electric current, and antifouling paints (containing zinc or copper, or slick surfaces such as epozy that make removal of mussels easier). Natural predators include diving ducks, crayfish, muskrats, and fishes with grinding teeth (carp, freshwater drum, pumpkinseed, round goby, bream, roach), eel, sturgeon, flounder. Nutrition
Filter a wide range of size particles, but select algae and zooplankton between 15-40 microns. Larval stages feed on bacteria. Reproduction
Zebra mussels are dioecious and fertilize externally; larvae are planktonic for several weeks before settling and attaching to substrate
Estimated at up to 1.5 million eggs per female per year; survival to adult stage may be less than 1%. Lifecycle stages
Fertilized egg hatches into trocophore (40-60 microns, 1-2 days), several stages of free-swimming planktonic veliger lasting 8-180 days (or longer in cold water), then at 350 micron size the larvae settle as plantigrade mussels, attach to substrate as juveniles, and may mature within the first year of life under optimal conditions; maturity in the second year is more usual. Zebra mussels live 3-5 years. This species has been nominated as among 100 of the "World's Worst" invaders Reviewed by: Major update under progress
J. Ellen Marsden, School of Natural Resources, University of Vermont, Burlington, USA.
Compiled by: J. Ellen Marsden, School of Natural Resources, University of Vermont, Burlington, USA.
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Last Modified: Wednesday, June 22, 2005
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