Dreissena polymorpha: A. Lateral view; B. Dorso-ventral view illustrating byssal threads; C. View of internal tissues; D. Cluster of mussels referred to as a “druse.”
Superfamily: Dreissenacea
Family: Dreissenidae
Genus: Dreissena
Species: polymorpha
Common name: Zebra mussel
Negative impacts: Biofouling potential for man-made and natural structures, competition with native species
Introduced Dreissenacea
Introduced to North America between 1986 and 1988.
Habitat:
· Attached to hard substrates in freshwater habitats. Also found colonizing soft sediments in Lakes Erie and Ontario.
· May also be found in pipes and grates associated with state, federal, and municipal facilities.
Size: Small, shell length up to 6 cm, average length of 1.5 cm
Life span: Short-lived (3-5 years)
Reproductive cycle:
· Dioecious with external fertilization.
· Larvae settle out of the plankton and attach to hard substrates with byssus as described (see Life History/Biology section).
Distinguishing characteristics:
Internal
· Myophore plate present anteriorly.
External
· Dorsally tapered shell valves.
· Epifaunal, attached to hard substrate.
· Umbone located anteriorly.
· Byssal threads present ventrally.
· Bottom flat or concave.
· Acutely angled ventral shell margin.
· Many color variations for shell valves.