The Coosa moccasinshell, Medionidus parvulus, is a small species of mussel that historically occurred in the Cahaba River, the Sipsey Fork of the Black Warrior River and the Coosa River, as well as tributaries in Alabama, Georgia and Tennessee. However, due to habitat loss and degradation, the species has disappeared from the mainstems of all of these rivers and persists in mostly small, localized populations throughout their tributaries.
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It is difficult to distinguish between the Alabama moccasinshell and Coosa moccasinshell, however, the posterior end of the Alabama moccasinshell is typically more pointed than that of the Coosa moccasinshell.
Freshwater mussels live an interesting multi-stage life cycle which depends upon a fish host to complete. Males release sperm into the water column, to be hopefully siphoned in by the incurrent aperture of the females, where the eggs held within her gills are then fertilized. Once the fertilized eggs start to develop, the female becomes inflated or gravid. The fertilized eggs develop into glochidia, which is the mussels larval stage. This stage requires a fish host for transformation into the juvenile stage, which sometimes requires a little coaxing by females. Glochidia are housed in packets called conglutinates and often mimic a food source of the fishes within that ecosystem to lure the fish to bite. Once the fish bites, the glochidia clamp down onto the fish, becoming encysted, and feed from the fish for several weeks until dropping off as juveniles.
The Coosa moccasinshell is believed to be a long term brooder, gravid from October to June.
The Coosa moccasinshell typically occupies sand, gravel or cobble shoals with moderate to strong currents in streams and small rivers.
A natural body of running water.
Although the diets of freshwater mussels are poorly understood, it is believed to consist of algae and or bacteria. Some studies suggest that the diets of freshwater mussels may change throughout their life, with juveniles collecting organic materials from the substrate though pedal feeding and then developing the ability to filter feed during adulthood. Pedal feeding is a form of deposit feeding where the animal uses their muscular foot to bury into the sediment, collecting organic matter. Filter feeding is a process by which mussels feed off of suspended organic material by pumping in water through their incurrent aperture and out through their excurrent apertures. In doing so they catch small suspended particles as food.
Many freshwater mussels spend the majority of their life sedentary and filter feeding on the bottom of rivers and streams. Sometimes they will bury into the sediment, only revealing a small portion of their aperture, which is used for gas exchange and filter feeding. The Coosa moccasinshell is believed to behave similarly to the Alabama moccasinshell, spending most of the time buried in the sediment, emerging only to display the female's modified mantle lure.
The Coosa moccasinshell has been historically reported from the Cahaba River, the Sipsey Fork of the Black Warrior River and the Coosa River, as well as their tributaries in Alabama, Georgia and Tennessee. Since this species was listed, its presence has been confirmed only in the Conasauga River, in Murray/Whitfield County, Georgia and Bradley County, Tennessee. Additionally at the time of listing, the species was also found in the tributary, Holly Creek, in Murray County, Georgia. Distribution is believed to be less than eight river miles in the Conasauga River and Holly Creek combined.
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