I am shiny, dark brown and have one to five distinctive spines on my upper and lower shell. As a full grown adult I can fill your whole hand. I am a type of pearly mussel found nowhere else but the Altamaha River and cannot be mistaken for any other kind of mussel. Just in case you have not guessed who I am, I am a candidate listed on the endangered species list know as the Altamaha Spinymussel (Elliptio spinosa) [Krueger].
The Altamaha spinymussel was first discovered near the mouth of the Altamaha River in Darien, GA, in 1836. This species are found in stable, coarse to fine sandy sediments of sandbars and sloughs, buried approximately two to four inches below the substrate surface, restricted only to swiftly flowing waters. Their historical range is restricted to the Coastal Plain portion of the Altamaha and the lower portions of its three major tributaries: the Oconee, Ocmulgee, and Ohoopee Rivers [Krueger].
Recent studies have shown a steady decline of the Altamaha spinymussel. No evidence of the spinymussels has been recorded since recent surveys dating back to 2001, which leads scientists to believe they are nonexistent. Only 10 of the 90 sites along the Ocmulgee River have presented life of spinymussels since 1993. Only 10 sites along the Oconee River have been conducted since 1993, which has lead to the thought of the spinymussel being extirpated from this river. The majority of the surveys conducted have been along the Altamaha River since 1993, only to produce the greatest number of individuals found at one site at any given time of nine.
The Altamaha Spinymussel, like other mussels, has limited mobility, which means they generally do not move more than a few dozen meters throughout their lives. In winter months, they burrow and remain inactive until summer months when the water temperatures begin to rise and avoid drought conditions. Due to their limited mobility, they are filter feeders and can filter 40 liters of water per day as an adult. The Altamaha Spinymussels filter certain types of algae, bacteria, and other microorganisms from the water [Johnson].
Spiny mussels have a very unique life cycle. Male mussels release their sperm into the water column towards the female in which the female uses her incurrent aperture (siphon) to obtain the sperm that then fertilize the eggs that are held in modified gills. The female larval mussels, known as glochidia, can be held by the female spinymussel for a few weeks or even over the winter; however, in order for the glochidia to complete their life cycle and become adult mussels, they need to attach to a fish host to transform into juvenile. The spinymussel reproduce in the late spring, by May or June. This is typically the season when the female is ready to release her glochidia, which are released in packets that resemble aquatic insect larvae that are ingested by fish. Instead of being ingested, the glochidia attach to the fish’s gills where they are encysted for two to four weeks before transforming into juvenile mussels. Shortly after their transformation, they detach from the fish and settle into the sediment where they will remain throughout their lives [Johnson].
Given the Altamaha Spinymussel’s preferred habitat in swift-moving water, they can be vulnerable to many predators as well as predation. “Juvenile mussels are highly susceptible to predation by parasites such as nematodes.” [Johnson] “Raccoons, otters, and muskrats are known predators of all freshwater mussel species.” [Johnson] However, human activities pose much more of a threat through sedimentation from certain land use practices, such as logging and agriculture (farming), which has been shown to be very devastating to mussels. Such sedimentation results in less food availability and respiratory problems. Plus, if severe enough, high increases in sediments to a stream could literally suffocate the mussels to death. Industrial effluent poses another threat due to their contents of toxic substances, which can be caused by thermal pollutions such as coal-fired and nuclear power plants usage of large volumes of river water for cooling purposes and then disposing the warm water back into the river; thereby, increasing the downstream water temperature which results in an increased frequency and intensity of algal blooms as well as lower dissolved oxygen levels [Johnson].
