zebra mussel
Dreissena polymorpha (Pallas)


Dreissena polymorpha or Zebra mussel are native to the drainage basins of the Black, Caspian, Aral and Azov seas. It has a small triangular shell with a sharply pointed umbo (hinge end). The prominent dark and light banding pattern on the shell is the most obvious characteristic. The outer covering of the shell is generally well polished, a light tan in color with broad, dark bands across the shell. These bands can be either smooth or zigzag in shape.
Life Cycle
D. polymorpha eggs hatch then go through planktonic larval stages for up to 4 weeks. Larvae are usually moved by water flow. Once larvae reach about 350 microns in size they develop into their juvenile stage. At this point they settle to the bottom and search for a substrate to attach to by a cluster of threads called a byssus. D. polymorpha reach maturity in 1-2 years depending on conditions. The life span can range from 3 to 9 years. Adult D. polymorpha can detach to seek out more favorable conditions. Synchronized spawning occurs in reproductively mature D. polymorpha. Spawning is usually triggered by water temperature.
D. polymorpha is considered one of the ‘World’s Worst’ invaders. They have been found in central and western Europe, Great Britain, North America, Russia and Scandinavia.
Control Efforts
Preventing infestations of D. polymorpha by proper ballast water management including mid-ocean exchange and disinfection should be a priority. Physical removal by high pressure washes can be effective. Freezing, heating to high temperatures and desiccation will control D. polymorpha.


Selected Images


EDDMapS Distribution

EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org

State Regulated List

State Regulated List - This map identifies those states that list this species on their regulated list. For more information, visit Invasive.org

Taxonomic Rank

Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Veneroida
Family: Dreissenidae
Genus: Dreissena
Subject: Dreissena polymorpha (Pallas)