Mollusc
ANS—Mollusc
Zebra Mussel
Description
Zebra Mussel- Dreissena polymorpha
- Has caused profound ecological changes in freshwater ecosystems where it is established, including losses of phytoplankton and microzooplankton
- Causes mortality of native clams and mussels
- Cost municipal and industrial water facilities millions of dollars to control
- If introduced into Montana will likely survive, become established and result in significant environmental and industrial damage
- Transported overland in bilges, livewells, motors and attached to boats and trailers
General Characteristics
- larvae not possible to see with naked eye
- newly settled larvae feel like sand paper on smooth surfaces
- juveniles are pepper corn size
- mussel with brown to black stripes
- adults can grow up to 2" long, typically are ¾" long
Links
US Geological Survey (USGS)—Zebra Mussel 
New Zealand Mudsnail
Description
New Zealand Mudsnail Distribution Map (USGS)
Key shows the size of New Zealand Mudsnails.- Potamopyrgus antipodarum
- Spread via stocking operations, by recreational anglers, or possibly aquarium release
- Reproduces asexually and thus it only takes one to start a new population
- Found in lakes and rivers
- Can close operculum to avoid desiccation
- Out competes native snails and other invertebrate
- May impact fisheries by reducing food availability
General Characteristics
- range in size from a grain of sand to 1/8" long
- color brownish to bluish-green
- operculum covers opening of shell, which is on left
- densities reported over 500,000 per square meter!
Links
US Geological Survey (USGS)—New Zealand Mudsnail
