Habitat:
Diet:
Main Threats:
Fun Fact:
Additional Information
The dwarf wedgemussel is a small, freshwater mussel that rarely exceeds 1.5 inches in length. It is the only Atlantic Slope freshwater bivalve (two-shelled) mussel in North America that has two lateral teeth on the right valve, but only one tooth on the left. The outer shell is dark brown or yellowish brown and often exhibits greenish rays in young mussels. The inner shell is bluish or silvery white. Dwarf wedgemussels feed by filtering small particles from the water.
The dwarf wedgemussel occurs on muddy sand, sand, and gravel bottoms in creeks and rivers of various sizes. This species requires areas with a slow to moderate current, little silt deposition, and well-oxygenated, unpolluted water.
Like other freshwater mussels, dwarf wedgemussel eggs are fertilized in the female as sperm passes over the gills. Fertilization typically occurs in mid-summer and fall, and release of larvae (glochidia) occurs the following spring and summer. Upon release, the glochidia attach to a fish host to encyst and metamorphose, later dropping to the streambed as juvenile mussels. Laboratory studies have shown the tesselated darter (Etheostoma olmstedi), Johnny darter (E. nigrum), and mottled sculpin (Cottus bairdi) to be glochidial host fish for the dwarf wedgemussel.
Threats to the dwarf wedgemussel include direct habitat destruction from damming and channelizing of rivers, and indirect degradation of habitat due to pollution, sedimentation, invasion by exotic species, and fluctuations in water level or temperature. Freshwater mussels, including the dwarf wedgemussel, are sensitive to potassium, zinc, copper, cadmium, and other elements associated with industrial pollution. Industrial, agricultural, and domestic pollution are largely responsible for the disappearance of the dwarf wedgemussel from much of the species’ historic range.
Distribution in New Jersey:
The dwarf wedgemussel occurs in Sussex and Warren Counties. The species formerly occurred in Morris, Essex, Bergen, and Mercer Counties. See Federally Listed Species Occurrences by Municipality and County [PDF].
Creeks and rivers
Particles filtered from the water
Dwarf wedgemussels spend their larval stages attached to the gills of a fish host.
Dwarf Wedgemussel (Alasmidonta heterodon) [endangered]
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Overview
The dwarf wedgemussel was federally listed as an endangered species in 1990.
Distribution
Species Range:
The dwarf wedgemussel is found in ten States from New Hampshire to North Carolina. The species is currently known to occur in 15 major drainages, comprising approximately 70 sites.