Mussel, ring pink

Obovaria retusa

phylum: Mollusca

class: Bivalvia

order: Unionoida

family: Unionidae

status: Critically endangered, IUCN Endangered, ESA

range: USA (Kentucky and Tennessee)

Description and biology

The ring pink mussel, also known as the golf stick pearly mussel, is a medium-sized mussel. The outer surface of its shell is yellow-green to brown in color. Inside, its shell is dark purple with a white border.

Like other freshwater mussels, the ring pink mussel breeds in a unique way. In the spring, males of the species release sperm, which is carried downstream by currents. As they are feeding, females take in this sperm, which fertilizes the eggs stored in their gills. Once the eggs hatch, the glochidia (pronounced glow-KID-ee-a) or larval forms of the mussel continue to develop in the gills.

After a while, the glochidia are released from the female's gills. They then attach themselves to the gills of a host fish (those glochidia that are unable to attach themselves sink to the river's bottom and die). The glochidia remain on the host

fish until they have grown and developed a shell. Once they have, the young mussels detach from the fish and sink to the riverbed where they bury themselves in the sand, leaving only their shell margins (edges) and siphons exposed.

A siphon is a tube through which the mussel feeds, removing plankton (microscopic plants and small animals) and other plant matter from the water. Because this is the only way it feeds, a mussel requires a river environment where there is not much current and very little silt. Too much silt (mineral particles) or sediment (sand and stones) in the water can clog a mussel's siphon and kill it.

Habitat and current distribution

The ring pink mussel is the most endangered of all North American freshwater mussels. It inhabits sections of the silt- free, sandy bottoms of the Tennessee, Cumberland, and Green Rivers in Tennessee and Kentucky. Biologists (people who study living organisms) are unaware of the total number of these mussels still in existence.

History and conservation measures

The ring pink mussel was once found in several major tributaries of the Ohio River. These stretched into Alabama, Illinois, Indiana, Ohio, Pennsylvania, and West Virginia. As indicated by its current small range, this mussel is in grave danger of extinction. Biologists believe the known remaining populations are all too old to reproduce.

As is the case with many other freshwater mussels, the ring pink mussel is disappearing because humans have tampered with its habitat. Dams built on rivers have caused upstream sections to become filled with silt. Downstream areas are subject to constantly changing currents, water levels, and water temperature.

Water pollution is another major threat, especially to remaining populations. Industrial wastes and pesticide runoff from farms are the main pollutants of the mussel's habitat.

Unless biologists discover new populations of the ring pink mussel in the wild, the future of this species is in doubt.