The spectaclecase (Cumberlandia monodonta) is a freshwater mussel that the U.S. Fish and Wildlife Service listed as an endangered species. It is found in the Mississippi, Missouri and Ohio River basins. The spectaclecase is considered a specialist species that requires very specific habitat needs, which limit its current range and distribution to certain sites within large rivers. Generally, mussels are long-lived, with individuals surviving up to several decades, sometimes up to 100 to 200 years. The oldest documented spectaclecase was thought to be 70 years old!
Major threats to the spectaclecase mussel include dams, small population size and fragmentation, sedimentation and pollution. Population losses due to dams have contributed more to the decline and potential extinction of the spectaclecase than any other factor.
Dams affect both upstream and downstream populations by disrupting seasonal flow patterns, scouring river bottoms, altering water temperatures and quality, and eliminating river habitat. Large rivers throughout nearly all of the spectaclecase mussel’s range have been dammed, leaving short, isolated patches of habitat between dams. Spectaclecase mussels likely depend on a fish, or other aquatic species, to move upstream. Because dams block
, mussels are also prevented from moving upstream. This isolates upstream populations from those downstream and leads to small, unstable populations. Consequently, these smaller populations are more vulnerable to other threats.Impoundment and channelization of rivers and streams further impacts these endangered mussels because of the increase in sedimentation and siltation. The 2014 recovery outline for the species notes that excess sedimentation, for example, reduces the feeding and respiratory efficiency of the mussels. Additionally, slow-moving deep water is created by impoundments which are perfect habitat for certain species such as the exotic zebra mussel, which poses a serious threat to native mussels.
The mostly sedentary lifestyle of these animals renders them more vulnerable to toxins and degraded water quality from pollution. Contaminants from accidental spill, factory discharge, sewage treatment plants and landfills and runoff from field feedlots, mines and construction sites can directly kill mussels. Indirectly, contaminants reduce the water quality, affecting the ability of surviving mussels to reproduce and lower the numbers of host fish.
Spectaclecase mussels are found in large rivers where they live in areas sheltered from the main force of the river current. This species often clusters in firm mud and in sheltered areas, like beneath rock slabs, between boulders and even under tree roots.
A natural body of running water.
Adult spectaclecase are suspension-feeders, siphoning water and feeding on suspended algae, bacteria, detritus, microscopic animals and dissolved organic material. Adult mussels spend their entire lives partially or completely buried within river bottom substrates.
The spectaclecase is a large mussel that can grow up to 9 inches in length. The shape of the shell is elongated, sometimes curved, and somewhat inflated, hence its name.
The life cycle of the spectaclecase is complex and includes a stage that is parasitic on fish or other host species. Males release sperm into the river current. As females siphon water for food and respiration, they also siphon sperm that fertilizes their eggs. Within special gill chambers, fertilized eggs develop into microscopic larvae called glochidia. After they mature, female mussels expel the glochidia, which must then attach to the gills or fins of a specific species, usually a fish, to continue developing into a juvenile mussel.
If glochidia successfully attach to a host, they mature into juvenile mussels and then drop off. If they land in a suitable area, glochidia grow into adult mussels. Using fish, or other aquatic species, as a host allows the spectaclecase to move upstream and populate habitats it could not otherwise reach. Two fish hosts for spectaclecase were confirmed in 2017, the mooneye (Hiodon tergisus) and the goldeye (H. alosoides). Host research is now focused on these two species, although efforts continue to identify additional hosts. Identification of host species now allows for propagation of juvenile mussels. Current research is focused on the husbandry of host fish and juvenile mussels in laboratory conditions.
Explore the information available for this taxon's timeline. You can select an event on the timeline to view more information, or cycle through the content available in the carousel below.