Are zebra mussels harmful11/18/2023 found that smaller mussels (5 - 10 mm) tend to move a greater distance (e.g. Juvenile zebra mussels also have special floating byssal threads allowing them to resuspend into the water column and drift to new locations. Īlthough generally considered nonmobile, if conditions become unfavorable, zebra mussels can detach their byssal threads and use their feet to seek more suitable habitat, particularly rough-textured structures. The zebra mussel lifespan is typically between two and nine years. All sizes of zebra mussels exhibit negative phototaxis and prefer darker locations such as crevices, corners and edges. Mature mussels commonly congregate into colonies called druses, which are often located in shaded areas. In North America, sexually maturity typically occurs at a length of approximately 8 mm, which frequently happens after just one year of growth. However, even after the development of the adult shell, zebra mussel juveniles are not classified as adults until sexually maturity. These developments facilitate the excretion and formation of the adult shell. The velum is replaced by fully functioning gill filaments and a mouth, and the foot moves to a new position and increases in size. Once initial settlement has occurred, veligers secrete byssal threads to attach to the selected substrate and undergo further development. After initial settlement, zebra mussels can relocate to more suitable locations. Veligers often have difficulty locating suitable substrate for settling, with mortality rates as high as 98%. Veligers will also settle upon macrophytes, as well as on other invertebrates. Suitable surfaces are generally hard structures, including both natural surfaces such as rocks and artificial surfaces such as cement, steel, or rope. Īlthough veligers can settle upon a variety of surfaces, survival is influenced by surface selection. At 16 to 88 days post-hatch, veligers begin to swim or crawl along the bottom in order to find suitable surfaces upon which to settle. While gill filaments will not become fully developed until later life stages, the foot is fully developed at the veliger stage and can be used either for swimming near or crawling along the bottom. After shell formation, organs, including a foot and gill filaments, develop in the mantle cavity. Within the first seven days post-hatching, veligers also develop an unornate D-shaped shell followed by a more ornate shell a few days later. Shortly after hatching, larvae, called veligers, develop velum, an organ used for feeding and movement. Larval zebra mussels undergo multiple stages of development, with corresponding shifts in behavior. Several days after fertilization, free swimming larvae emerge and disperse throughout a waterbody. Within a year, one female can produce and release over a million eggs. A single female zebra mussel releases 30,000 to 40,000 eggs per spawning event. Spawning continues as long as temperatures are adequate, even into early fall. Spawning of sexually mature zebra mussels begins when water temperatures reach 12˚C with optimal spawning temperatures near 18˚C. Both eggs and larvae are capable of movement by either natural or anthropogenic means. Infestation of zebra mussels into new waterbodies is generally believed to occur during early life stages because of external fertilization of eggs in the water column and free-swimming larvae. Zebra mussels can attach directly to native North American mussels, which frequently leads to native mussel mortality. In addition, zebra mussels are epifaunal, using byssal threads to attach to hard surfaces and substrates not available to native mussels, which are infaunal and typically bury themselves in sediments. In contrast, native mussels must rely on host species to complete development. Dreissenid mussels have planktonic larvae that do not require a host to develop. Zebra mussels belong to the Dreissenidae, a mussel family possessing characteristics not found in native mussels. Sphaeriidae, Margaritiferidae and Unionidae are the only families of freshwater mussels native to North America, with Unionidae being the most common. Zebra mussels exhibit high fecundity and an ability to attach to a variety of surfaces that has allowed them to spread quickly and colonize new locations. It inhabits large freshwater lakes and rivers but has also been found in a wide variety of aquatic habitats, including flooded quarries, cooling ponds, and golf course ponds. It is a small, brown, freshwater mussel with a cream-colored zebra stripe pattern that varies among individuals. The zebra mussel Dreissena polymorpha is a bivalve native to eastern Europe.
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |