User:Longmv/Lasmigona

Lasmigona
Lasmigona is a genus of freshwater mussels, aquatic bivalve mollusks, in the family Unionidae. They are found in freshwater systems within North America, primarily in the eastern United States.

Species
Lasmigona alabamensis

Lasmigona complanata

Lasmigona compressa

Lasmigona costata

Lasmigona decorata

Lasmigona etowaensis

Lasmigona holstonia

Lasmigona subviridis

Description
The shells of adult Lasmigona can range from small (60 mm) to large (200 mm). They generally live over 10 years, sometimes several decades, and are relatively sedentary organisms. Although they are free-living, they fix themselves into the substrate on the bottom of stream beds. Often, many individuals will be in the same area, forming large "mussel beds".

Life Cycle
Adult Lasmigona are free-living, but their larval stage, called glochidia , is parasitic. The glochidia require a fish as a host while it metamorphoses into a juvenile. Adult females release glochidia into the water from their gills. There are hooks on the glochidia to help them attach to the gills or fins of fish as they swim by, which must happen within 1-2 days of the glochidia being released. After metamorphosing into juvenile mussels, they drop off the fish and begin their lives as free-living filter-feeders.

Ecology
Freshwater mussels, including Lasmigona, play an important role in the health of freshwater ecosystems. They are filter feeders that remove particles from flowing water and, in turn, deposit nutrients. Entire streams can be filtered when large mussel beds are present. These beds occur in areas of a stream that has flowing water slow enough to allow them to settle at the bottom, but fast enough that sand does not completely cover them. This narrow requirement and inability to move great distances makes them sensitive to changes in their environment.

Conservation Concerns
Over 70% of freshwater bivalve species in North America are considered endangered, threatened, or of special concern. Within Lasmigona, the International Union for Conservation of Nature lists one species, Lasmigona decorata, as critically endangered, but two other species, Lasmigona subviridis and Lasmigona holstonia, as decreasing and one other species, Lasmigona compressa, as unknown. The primary threats to all freshwater bivalves, including Lasmigona, are stream pollution, stream alterations, particularly those that cut off head waters and decrease water flow and increase sedimentation, and invasive species, such as the zebra mussel. A threat unique to freshwater bivalves is the loss of host fish species. Most mussel species can only use one or a few specific species of fish as a host during the glochidial stage. Declines in fish populations threaten the respective mussel populations that rely on them.