Appalachian elktoe

Taxobox
name = Appalachian elktoe


status = CR | status_system = IUCN2.3
regnum = Animalia
phylum = Mollusca
classis = Bivalvia
ordo = Unionoida
familia = Unionidae
genus = "Alasmidonta"
species = "A. raveneliana"
binomial = "Alasmidonta raveneliana"
binomial_authority = (I. Lea, 1834)
synonyms =

The Appalachian elktoe, scientific name "Alasmidonta raveneliana", is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.

=Physical Characteristics=The Appalachian elktoe has a “thin, kidney-shaped shell, reaching up to about 10 centimeters (4 inches).” Younger mussels normally have a yellowish-brown periostracum (outer shell) while more mature mussels generally have a dark brown to greenish-brown periostracum. Features on the outer shell of the mussel, whether juvenile or adult, are often fine or hard to distinguish. In some cases streaks or waves are apparent, which are most easily noticeable on the dorsal region of the outer shell. Most individuals however have green waves, which are a similar hue as the rest of the shell and are often minute. The shell nacre (inside shell surface) has a sheen of white, blue, and silver. The center of the inner shell changes from a light, almost translucent shine, to a more pink or tan. Some species have irregular spots or blotches in the center of the nacre that are much darker than the lining of the shell. (Fridell)

Habitat

Despite the rarity of the species and the lack of information regarding the Appalachian elktoe, their habitat is one that is very easily studied because of the similarity to other species of freshwater mussels. The Alasmidonta raveneliana have been found mostly in shallow to medium sized creeks or rivers. Cooler temperature water is what they prefer, along with fast-flowing to moderately-flowing currents. They can be found near sections of the water where there is more rock or gravel at the bottom as opposed to water that flows over areas with a lot of clay or silt at the bottom. Also, Appalachian elktoe do not survive well in areas of streams with clay or silt moving through the current. The species has been found in areas with varying sizes of rock such as sand, gravel, and boulders, and ideally are in an area that has a combination of all three. Appalachian elktoe need stability in order to survive so they are not in any areas where there is shifting gravel or bedrock. Shifting bedrock threaten the survival of the mussels when they are in their habitat. (Fish and Wildlife Service)

Life Cycle

Many aspects of the Appalachian Elktoe are unknown. The species is hard to find, and populations are only decreasing. Currently, we are unaware of what the Appalachian Elktoe feed on, what fish they use as host fish, or how long their life span is. We do know, however, that this is a very sensitive species, making it difficult to study. (Fridell)

Like other mollusks, the Appalachian Elktoe feeds itself by picking out particles of food that are in the water. The specifics of their diet has yet to be determined, but it has been assumed that the Appalachian Elktoe survives off the same things as other freshwater mussels: detritus, diatoms, phytoplankton, and zooplankten (Churchill and Lewis, 1921).

The reproductive cycle of the Appalachian Elktoe is also similar to other native freshwater mussels. First, the male releases a trail of sperm into the water column. Then, when females come in contact with the sperm, they take it in through their siphons. Normally this process occurs during either respiration or feeding. Once the females have taken the sperm in, they retain it in their gills until the larvae (glochidia) have matured and are fully developed. After the larvae are ready, they are then released from the female’s gills into the water. Shortly thereafter, the baby mussels will find a host fish to live off of for a while. When the mussels have grown into juveniles, they will then detach themselves from the host fish and continue maturation on their own. This stage of the mussels’ life-cycle is one that not all mussels go through. In order for the mussels to survive the separation from the host fish, they need to detach themselves in a suitable area. Only of species of fish has been identified as a host fish for the Appalachian Elktoe: the Banded Sculpin or Cottus carolinae. (Fish and Wildlife Services)

Distribution

The Appalachian elktoe are endemic to mountain river streams in Western North Carolina and Eastern Tennessee. Although historical information is unavailable, it is believed that the species once lived in a more vast area in larger creeks and streams of the upper Tennessee River systems. Currently, the Appalachian elktoe has very fragmented populations. The mussels survive in scattered sections of suitable habitat in portions of the Little Tennessee River system, Pigeon River system, the Little River in North Carolina and the Nolichucky River system in North Carolina and Tennessee. In the Little Tennessee River system in North Carolina, populations survive in the reach of the main stem of the Little Tennessee River, between the city of Franklin and Fontana Reservoir, in Swain and Macon Counties (Service 1994, 1996; McGrath 1999; Fridell, pers. observation, 2002), and in scattered reaches of the main stem of the Tuckasegee River in Jackson and Swain Counties, from below the town of Cullowhee downstream to Bryson City (M. Cantrell, Service, pers. comm. 1996; Fridell, pers. observation 1996, 1997; McGrath 1998; T. Savidge, North Carolina Department of Transportation (NCDOT), pers. comm. 2001).

The populations in each of these rivers are small and range from two live mussels to fifteen. Normally however, averages of only two to four mussels are found together at the same site of these river systems. The species continues to be very spread out in where they survive. This can make it difficult to find Appalachian elktoe in their habitat, especially when there are only two or three mussels per site. Historically, the geographic range of the species was broader and ranging from Tulula Creek, the main stem of the French Broad River, and the Swannanoa River, but the Appalachian elktoe have not been spotted in these bodies of water recently, and it has been assumed that they no longer inhabit the areas. It has also been documented that the species used to live in the North Fork Holton River in Tennessee. Later studies at that site then proved that a similar species of mussel was found in the area, but not the Appalachian elktoe. It is still somewhat of a mystery as to whether the species actually did at one time live in the North Fork Holston River, but even so, the species will not be found in that area today. As of 1996, only two populations of Appalachian elktoe were known to be surviving. One of the populations was found in the main stem of the Little Tennessee River, and the other was found scattered about in the main stem of the Nolichucky River in various counties of North Carolina. (Fridell)

Endangerment

The Appalachian elkoe was added to the Federal Register of Endangered Species on November 23rd, 1994. The exact cause for the declination of the species is unknown. Many factors have been attributed to the endangerment such as siltation from logging, mining, common agricultural practices, and also area construction work. Run-off into the river systems can seriously affect the species survival since the mussels only live in clean, well-oxygenated streams. The run-off and discharge of pollutants from industrial, agricultural, and municipal sources can cause major damage to the sensitive species. Human alterations of the species’ habitat, such as dredging, damming, and other forms of channel manipulation, also have been attributed to declining populations. Changing aquatic environments without the proper sedimentation control, not only affects the mussels, but most other freshwater species as well.

Mussels are somewhat stationary creatures. They are unable to move long distances, which is why they live in very specific, stable habitats that fulfill all of their needs. Their immobility is hindering their survival because they are unable to adapt to constantly changing aquatic environments. When their habitat is constantly being tampered with, they are unable to fully develop and reproduce. Interestingly, the species was first noticed to be declining in populations after hurricanes Frances and Ivan hit the Southeastern region of the United States in the early 1990s. Although the landscape was changed due to the high winds and heavy rain of the hurricanes, the storms did not directly affect the mussels. Naturally occurring storms such as hurricanes are not threatening to the Appalachian elktoe. When humans tamper with the naturally occurring state of the streams however, it is very difficult for the Appalachian elktoe, as well as other mussel species, to remain active. (Shaw)

Siltation in the rivers is one of the biggest threats to freshwater mussels. Naturally occurring siltation usually does not bother the species because it is on a much smaller scale. Siltation caused by human interaction both directly and indirectly affects mussels. Siltation causes the natural patterns of the rivers to change. It can create mounds on the bottom of the streams which not only cover the rocks that mussels prefer to live by, but also creates areas in the water that are difficult for the mussels’ host fish to swim causing serious species fragmentation. Siltation also degrades the quality of the water, and exposes mussels to many more pollutants than they are naturally exposed to. A study done in 1936 found that even one inch of unnatural sedimentation in the habitat causes high mortality rates in most mussels including the Appalachian ekltoe (Ellis). Juveniles and reproduction are also seriously affected by even a small amount of sedimentation. When the clean, well-oxygenated water of the mussels’ habitat gets certain amounts of sedimentation, the juveniles are not able to develop properly because the silt clogs the gills of the host fish that they parasitize themselves on. Most mussels are sensitive to many pollutants. Some of the most harmful pollutants to the mussels come from different forms of heavy metal, higher than normal concentrations of nutrients, and chlorine. (Vaughn)

Because of the irregularity of the Appalachian elktoe’s, and similar species of mussel’s habitat, over 144 miles of river area in Western North Carolina and Eastern Tennessee were deemed critical habitat on September 27th, 2002. Critical habitat is an area that the government has reserved for monitoring and protecting in efforts to save species currently inhabiting that area. By declaring the Appalachian elktoe’s habitat critical, it allows for management plans to be fully implemented and for penalties or fines to be created for partaking in activities that may lead to the species’ decline. (Vaughn)

Recovery Plan

In August of 1996, a recovery plan was published in order to save the endangered mussels. It is a regional plan that includes all areas where the species currently live and also areas where the species has been thought to live in the past. The ultimate goal of the recovery plan is, of course, to delist the species from the Endangered Species List. Presently the Appalachian elktoe are now considered critically endangered and it is unknown if they are still actively reproducing. Originally when the recovery plan was made, the species was supposed to be down-listed from endangered to threatened. There are four main steps to the recovery plan that promote the delisting of the Appalachian elktoe. The first step is, whether by establishing new populations or by protecting existing populations, to have at least four stable populations of Appalachian elktoe surviving in sites that are thought to be in their historic range. Ideally there will be one population in each of the Little Tennessee, French Broad, and Nolichucky River systems. The second step, which can only be accomplished after the first step is deemed a success, is to create different age groups of the mussels in these river systems. Three age groups must be surviving in order for a population to keep reproducing: juveniles, adults, and developing larvae (glochidia). The third step in the recovery plan is to keep all the new populations of mussels in stabilized and unthreatened habitat. This will be done by monitoring the streams frequently and protecting them from threatening factors of the past, as well as possible threats that might occur in future instances. The fourth and final step to recovering the Appalachian elktoe is to maintain stability in all four populations, and possibly have them increasing by the next ten or fifteen years. (Hoggarth)

In order for the species to be completely delisted, more criteria must be met. Instead of only four viable, reproducing populations of Appalachian elktoe, there must be a least six that are surviving on their own. Like the initial recovery plan, ideally there will be at least one population in the Little Tennessee, French Broad, and Nolichucky River systems. The next requirement is to have at least three age classes in each of the six populations. This includes a whole age class of juveniles and gravid females to make sure reproduction is occurring and occurring steadily. Once this goal is met, the next requirement for delisting is to make sure that the habitats of these populations are not in danger or susceptible to habitat destruction. Finally, like that last requirement in the first recovery plan, the last criteria for delisting is that all six populations remain stable and hopefully increasing steadily within a period of ten to fifteen years. (Fish and Wildlife Servces)

In order to take all the necessary steps in these recovery plans, some actions need to be taken. The first and most important action to saving the Appalachian elktoe is to utilize legislation and keep the species protected at all times. Along with informing local and federal legislation about the endangered species, the public needs to be informed as well. Education programs on mussels in the Southeastern region of the United States are crucial not only for the survival of the Appalachian elktoe, but also for the survival of other similar endangered mussels in the area. Another very important action to take is constant monitoring of the existing populations as well as searching and controlling developing populations. Monitoring the species is crucial in recovery, but unfortunately not a lot of information has been collected on the Appalachian elktoe. In order to fully benefit from all the steps of the recovery more information must be found. This is one of the most important actions needed to be taken. Ideally, the species’ historical records, habitat requirements, and threats will all be found over the course of the recovery plan. By determining important factors such as previous distribution and exact diet, it will allow us to use the most valuable information on how to save the Appalachian elktoe. Discovering this information also will allow us to implement valuable and informative management plans. (Fish and Wildlife Services)

The costs of the recovery plan were originally unknown. Because of the lack of information on the species, we do not know exactly what funding needs to be spent on and also how much. It is estimated that the costs will increase annually over the ten to fifteen year period. This is so because as more research is found, hopefully we will have established more species which will require more funds. The costs of this recovery are difficult to establish also because it normally takes mussels until age five to start reproducing, therefore a full ten years is needed to study reproduction rates and what affects them. (Hoggarth)

References

1996. Recovery plan for the Appalachian elktoe (Alasmidonta raveneliana) Lea. U.S. Fish and Wildlife Service, Atlanta, Ga. 31 pp.2002. Endangered and threatened wildlife and plants; designating critical habitat for the appalachian elktoe.Bauer, G, Hochwald, S and Wilkenat, W 1991 Spatial distribution of freshwater mussels the role of host fish and metabolic rate - Freshw Biol 26 377-386

Department of Interior. U.S. Fish and Wildlife Service. 1994. Endangered and Threatened Wildlife and Plants; Appalachian Elktoe Determined to be an Endangered Species. Federal Register 59(225):60324-60334.Fridell, J. A. 1999. Appalachian elktoe in north carolina.Hoggarth, M. A., D. A. Kimberly, and Van Allen, Benjamin G. 2007. A study of the mussels (mollusca: Bivalvia: Unionidae) of symmes creek and tributaries in jackson, gallia and lawrence counties, ohio. Ohio Journal of Science 107(4):57. Howard, J.K., K. M. Cuffey. 2006. The functional role of native freshwater mussels in the fluvial benthic environment - Freshw Biol 51 460-474Neves, R. J., A. E. Bogan, J. D. Williams, S. A. Ahlstedt, and P. W. Hartfield. 1997. Status of Aquatic Mollusks in the Southeastern United States: A Downward Spiral of Diversity. in G. W. Benz and D. E. Collins, editors. Aquatic Fauna in Peril: The Southeastern Perspective.Shaw, K. M., T. L. King, W. A. Lellis, and M. S. Eachles. 2006. Isolation and characterization of microsatellite loci in alasmidonta heterodon (bivalvia: Unionidae). Molecular Ecology Notes 6(2):365.Strayer, D. L., J. A. Downing, W. R. Haag, T. L. King, J. B. Layzer, T. J. Newton, and S. J. Nichols. 2004. Changing perspectives on pearly mussels, north america's most imperiled animals. Bioscience 54(5):429. Vaughn, C. C., C. M. Taylor. 1999. Impoundments and the Decline of Freshwater Mussels: A Case Study of an Extinction Gradient. Conservation Biology 13(4): 912-920.