Zebra Mussel
Zebra Mussel
Dreissena polymorpha
Dreissena polymorpha
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Population, Conservation Status, Threats:
Zebra mussels are considered least concern by the IUCN, and their numbers are actively increasing. While concern for this species' survival is minimal, the impacts of this species' rapid reproduction and colonization of North America is of great concern. Zebra mussels are wildly invasive, capable of outcompeting native mussels across the United States and clogging infrastructure, causing millions of dollars in damage yearly, and reducing native biodiversity.
Physical Description:
Zebra mussels are small, rarely exceeding 1.5 inches, possessing a triangular shell with a flat underside. They are named for the alternating dark and light stripes commonly seen on their shells, though all-light or all-dark individuals also exist. They also posses a tuft of threads called byssal fibers on the hinge of their shell which allows them to firmly attach to surfaces, something that is generally not seen in native species.
Parts of the United States known to to contain zebra mussels from the United States Geological Survey. Zebra mussels are native to freshwater habitats in southern Russia and Ukraine, but have become an invasive species in many countries.
Habitat:
Zebra mussels are incredibly adaptable, able to live in freshwater environments across the world. In the United States, they have been found across the eastern half of the country, and are likely to expand into the rest of the country if measures are not taken to mitigate their spread.
Behavior:
Adult zebra mussels are sessile, attaching themselves to surfaces with their strong byssal fibers. They have been known to congregate on top of native mussels and essentially smother them. Their economic impact to both infrastructure and recreation is significant; large concretions of mussels can clog water intake structures and pipes and damage boats. Dead mussels may also wash up on beaches, creating a foul smell as their shells pose a hazard to bare fee, reducing recreation. One of the characteristics making them particularly well-suited to colonizing new environments is their ability to survive long periods of time out of the water - up to two weeks in humid conditions.
Diet:
Zebra mussels are incredibly efficient filter feeders, and phytoplankton and other suspended particulates make up a large portion of their diet. Their efficiency means they are able to quickly outcompete other species for food, and leave water clearer, which promotes the growth of aquatic vegetation and toxic algae, which they do not feed on.
Reproduction:
One female mussel is capable of producing over 30,000 eggs per reproductive cycle, adding up to a potential total of more than a million eggs per year. Fertilized eggs hatch into free-swimming larvae called veligers, which can survive for up to a month in the water column before finding a surface and anchoring themselves to it. Young mussels tend to colonize hard surfaces together in large groups, creating clusters which can be problematic for other species and human machinery.
Associated Species:
Zebra mussels look similar to the related, and also wildly invasive, quagga mussel. The spread of zebra mussels across the world has been facilitated by human transportation activity, and their economic impact to human infrastructure is of great concern. Zebra mussels pose an existential threat to many native freshwater mussel species across the United States.
Illustration by Willow Sedam
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