There are three main periods in the zebra mussel life cycle: the larval, juvenile, and adult stages. The larvae are planktonic (float in water column) during their initial three life stages: trochophore, straight-hinged veliger, and umbonal veliger. Larvae eventually settle on a substrate during their pediveliger stage, and move only by crawling during their plantigrade stage. The pediveliger is considered by some to be the final larval form, with the plantigrade as a stage between larval and juvenile stages (Ackerman et al. 1994). These stages are identified primarily on morphology and behavior and are somewhat variable and overlapping in physical dimensions. The amount of time required for a fertilized gamete to develop into a fully developed juvenile is longer at colder water temperatures and thus can range from 8 to 240 days (Nichols 1996).
The zebra musselís clam-like shape throughout much of its larval stage is replaced by a more triangular or mussel-like shape as it enters the juvenile stage. Mussels are considered adults when they become sexually mature. Adult mussels range from approximately 6 to 45 mm and generally live to be 2-3 years old in temperate climates.
Life History and Biology Introduction
Fertilization and Trochophore Stage
Juvenile and Adult Stages