Carolina heelsplitter

Taxobox
name = Carolina heelsplitter


status = CR | status_system = IUCN2.3
regnum = Animalia
phylum = Mollusca
classis = Bivalvia
ordo = Unionoida
familia = Unionidae
genus = "Lasmigona"
species = "L. decorata"
binomial = "Lasmigona decorata"
binomial_authority = I. Lea, 1852
synonyms =

The Carolina heelsplitter, "Lasmigona decorata", is a species of bivalve in the Unionidae family. It is endemic to the United States.

Found in only North Carolina and South Carolina, the species has been appropriately named the Carolina heelsplitter. The scientific name of the Carolina heelsplitter is "Lasmigona decorata". This species current status is classified as critically endangered. The IUCN Red List website states that to be considered critically endangered means that the species is facing an extremely high risk of becoming extinct in the wild in the immediate future. For more information on status definitions visit [http://www.iucnredlist.org] .

Description

The first recorded encounter with the Carolina heelsplitter was in 1852 by a man named I. Lea. Lea described this new creature as "Unio decoratus". The largest recorded specimen was about five inches long.

As for the appearance of the Carolina heelsplitter, it is described with an outer shell of greenish-brown to dark brown in color, and a usually pearly white or bluish white nacre. The nacre isn’t always found in shades of white, but has been known to be pale orange in the older specimens of the species. Also, the younger heelsplitters tend to have rather faint black or greenish-brown rays found on their outer shell.

The medium-sized mussel of the Carolinas has well-developed, yet thin, lateral teeth that are somewhat delicate. The Carolina heelsplitter also has two blade-like pseudocardinal teeth in the left valve and one in the right valve.

With an “ovate, trapezoid-shaped, unsculptured shell“, the size of largest Carolina heelsplitter runs at about 4.6 inches in length and 1.56 inches in width. The height for that particular mussel of this species was 2.7 inches tall.

Endangered Species Act and Recovery Plan

The Carolina Heelsplitter, "Lasmigona decorata", was determined to be endangered on Wednesday, June 30th, 1993. In the final document the reasons stated were for “Present or threatened destruction, modification, or curtailment of its habitat or range”, “over utilization for commercial, recreational, scientific, or educational purposes”, “disease or predation”, “the inadequacy of existing regulatory mechanisms”, and “other natural or manmade factors affecting its continued existence”. After first being listed there has since been a review of the species and how it has been recovering. The review of the species was dated July 28th, 2006.

The original recovery plan written for the Carolina heelsplitter was officially recognized in January 1997 and was written by John A. Fridell. The major points of the recovery plan for the Carolina heelsplitter were using government regulations to protect the species, creating educational opportunities, continue to search for new populations, establish six viable populations, and to alleviate threats proving as major issues to the species, with the final objective to get the species delisted.

When the recovery plan was written, there were only four known populations of "Lasmigona decorata", stating that the populations appeared to have extremely restricted distribution and that much of the habitat in the species historic range (Catawba, Pee Dee, Saluda, and Savannah River systems) is now unsuitable for the reintroduction of the species. The recovery plan also stated that it was very important that the species were extensively enough established so the population couldn’t be completely wiped out by one major event involving the habitat in which they lived in.

Reproduction

Like most mussels, the reproductive cycle begins when the male Carolina heelsplitter releases its sperm into the stream. Soon afterwards the sperm is taken in by the females, a process which is called siphoning. The female's eggs, which will be carried in the females gills, then become fertilized. When the glochidia (larvae) are fully developed the female mussel releases them into the water, then the larvae are on their own. Soon after being set free into the water system, the baby Carolina heelsplitters must attach themselves quickly to a body part of their host fish, which is not harmed in the process. In this particular case the host fish is still unknown. The heelsplitters then receive the oxygen and other needs from the fish host for several weeks. When they have grown and turned into fully developed juvenile mussels, they release themselves from the fish host and settle into the stream or river.

A fish host is very important to all mussels, not only because it provides the younglings with food and oxygen, but also because it serves as a mode of transportation. The transportation of the mussels is key when attempting to create new populations in streams and river banks. Not much information is know about the fish host of the Carolina heelsplitters, in fact the fish host hasn’t been pinpointed as an exact species of fish yet.

Location and Distribution

The Carolina heelsplitter enjoys living in shallow streams and rivers, even the occasional pond. The species can usually be found in mud or some mixture or mud and another type of sediment. The heelsplitter are generally found along stable stream banks, but have also been found in the middle of a water way. It is also important that the water isn’t carrying much sediment.

Historically the Carolina heelsplitter was known to be found in the Catawba and Pee Dee River systems in North Carolina, and the Pee Dee and Savannah River systems of South Carolina. It is also possible that they historically lived in the Saluda River systems located in South Carolina.

As for where they are presently located, there are now ten known populations prior to the 2007-2008 drought in North Carolina and South Carolina. The areas include Goose Creek and Flat Creek in the Pee Dee River system, Waxhaw Creek, Sixmile Creek, Gills Creek, Fishing Creek, and Bull Run Creek in the Catawba River system, and Red Bank Creek, Turkey Creek, and Cuffytown Creek all located in the Saluda River system.

John A. Fridell states the numbers of individuals in each and every one of the populations indicate very low numbers. The number of individuals found in each of the populations for resent surveys are as follows (please allow room for error):
*1-17 individuals were found in eight of the known populations, with only 1-5 individuals being found in four of these eight populations.
* 26 individuals were found in only one population
*The largest population included only 42 individuals.

The numbers of individuals that the surveyors found also indicate that the species is in decline number wise, and also that none of the populations have improved over time. John A. Fridell also mentions that the populations are very highly fragmented and isolated, and that they have also only been found in short stream reaches of eat other.

Many combined influences are connected to the decline and endangerment of the Lasmigona decorata populations. The biggest reasons for their critical endangerment deal with sedimentation and stream pollution, road construction and maintenance, runoff, mining, and several other human inflicted problems.

Threats and Reasons for Endangerment

Population Size

One of the main reasons that the Carolina heelsplitter has such a high risk of going extinct is its population size. As stated in the Location and Distribution section, the number of individuals in each population is very low, creating a lack of genetic diversity currently and later on in future years not giving them enough genetic material to adapt properly to natural and manmade events among other things. Genetic diversity is very important if you want a species to survive. It increases the chance of survival by allowing enough variability that if a new virus came wreaking havoc on a species, it hopefully won’t wipe out the entire population due to that diversity.

Not only do the populations have very few individuals, but they are also located at a far enough distance from one and other that they have little opportunity to mingle and share genes. This also poses a problem when a disaster happens in one area because the other existing populations are highly unlikely to be able to repopulate in that area.

Water Pollution

Just like humans, clean and unpolluted water is very important to the Carolina heelsplitters. For this species of mussel, pollution has more than one form. One of the biggest is the ordeal of chemical water pollution.

Chemical water pollution can include runoff, dumping trash or chemicals into the stream and rivers, and several other things. Toxic substances in the mussel’s water ways was listed as one of the top five stressors mussel species, as well as habitat degradation and decline in water quality as being the some of the biggest causes in the decline of most mussel species.

One report in particular, studying out of North Carolina, studied the water quality and how it affects all stages of the mussel life. The study showed that mussel larvae and juveniles are extremely sensitive to high levels of copper and ammonia, but seem to be okay with higher levels of chlorine. The most elevated levels of ammonia were found at the stations at Goose Creek, as well as the highest chlorine and copper levels were located at Goose Creek. The research group thought that the higher levels of copper were due to higher suspended sedimentation because of a recent rain downpour.

Goose Creek remained to have the biggest problems with inorganic pollutants, many of the results showing that levels were at chronic exposure levels leaving Goose Creek to still be at risk for pollution effecting the living organisms within it, not to mention the high levels of all the tested pollutants can have a monumental effect on the recovering populations of the Carolina heelsplitters.

Habitat Degradation

Another important factor is the habitat for this species. The Carolina heelsplitter is now found in shallow streams and rivers ranging from about one to four feet deep. The water has to be clear, without culverts, dams, or anything that might obstruct the flow of the river. It is also an absolute must that the rivers have high oxygen content with a lot of microscopic organisms and plants to feed on. And the fact alone that they need very stable river or stream banks to live on says a lot about the sensitivity of the species. Stable beds and clear water are two things that these mussels cannot live without, and that is why habitat degradation is an important issue to acknowledge with "Lasmigona decorata".

Crumbling banks not only take away home for this group of mussels, but it also pollutes their water in a different way. A stable stream bank system includes many plants and trees near the stream banks to hold the soil and sediment in place with their roots. Any rise of silt or sediments in the rushing water can have a detrimental effect on the species. The biggest issue is that when too much of the sediment is flowing with the river water, it can cause the Carolina heelsplitters to suffocate and die. And since the populations and not get up and leave, it is very important that measures are taken to ensure that the waters ways and surrounding area are not disturbed so much as to cause the suffocation of the mussels.

Developing areas around the rivers greatly disturb the delicate balance of the carried sediment in the water. If a city decides to cut down the habitat near a part of the river, the soil runoff can be enough to cause a problem with the sediments running with the river, as well as construction like building and demolishing bridges and roads. Anything that can potentially disturb the water will be an issue that has to be dealt with. The Carolina heelsplitters sensitivity to increased sedimentation can be quite the obstacle to overcome when cities are always wanting to expand and people of all types want to develop and use the land around them. Not to mention that increased sedimentation blocks out sunlight from reaching the bottoms of the rivers and streams.

The vegetation along the river and stream sides also help regulate the water’s temperature during the long and hot summers. It also provides decaying leaves and plants that are an essential part to the survival of all organisms living in the water. The death plants and leaves that surround the area of the water way provide a major source of food to the creatures living in the river or stream.

Expansion and Development

Both expansion and development greatly effect the Carolina heelsplitter, as it does most species. One problem that directly harms the Carolina heelsplitter is that of channelization, impoundments and stream dredging. This harms them by directly destroying the Carolina heelsplitter’s habitat.

Another big issue is when the land around the streams is developed for whatever purpose it is developed for, most likely for growing cities like Charlotte, North Carolina. Forestry and agriculture are also having a big impact of the species due to lack of forest buffer zones left behind and runoff of pesticides and excess sediments into the rivers and streams that are home to the Carolina heelsplitters.

Poorly regulated development from cites and agriculture pose the biggest problem when trying to keep the water quality at a high enough level to support the life of the Carolina heelsplitter. Resulting in more wastewater discharges and less healthy water for the entirety of the ecosystem.

Another important aspect of what we know about the Carolina heelsplitter can help not only the environment directly around them, but it can also benefit humans. Mussels are a good indicator of water quality, the better the water, the higher the number of mussels. We know that one of the leading causes of the declining of this species is because of water pollution, and it’s not just the big corporations and companies that are polluting it, we all have a hand in polluting the earth around us. We may not notice it yet, but more sensitive species are already being affected by how humans are altering the environment. If we try to help out the Carolina heelsplitters by keeping their water ways clean and with fewer chemical toxins, we not only help them out but we also benefit from the act of it ourselves.

Not all that much is known about the Carolina heelsplitter, making it a lot more difficult to save from extinction. One area that really needs to be looked into is to finding out what species of fish serve as the fish host for the Carolina heelsplitters. Once it is found out what fish carry the mussel’s larvae, we might be able to find out another reason as to why they are so critically endangered. If the fish host is endangered or over fished , we could cook up new measures to help protect and increase the number of that fish and by doing so, that could also help out Carolina heelsplitters and other mussels along the way.

ources

* Bogan, A.E. 1996. [http://www.iucnredlist.org/search/details.php/11360/all Lasmigona decorata] . [http://www.iucnredlist.org 2006 IUCN Red List of Threatened Species. ] Downloaded on 07 August 2007.

* Bogan, A.E. 1996. Lasmigona decorata. In: IUCN 2007. 2007 IUCN Red List of Threatened Species. [http://www.iucnredlist.org] . Downloaded on 27 April 2008.

* "Carolina heelsplitter." Species Profile. U.S. Fish and Wildlife Service. [http://ecos.fws.gov/speciesProfile/SpeciesReport.do?spcode=F02L] .

* U.S. Fish and Wildlife Service. 1996. Carolina Heelsplitter Recovery Plan. U.S. Fish andWildlife Service, Atlanta, GA.

* "The Carolina Heelsplitter in the Carolinas." Library.fws.gov. December 2002. U.S. Fish and Wildlife Service. [http://library.fws.gov/Pubs4/carolina_heelsplitter.pdf] .

* Price, Jennifer. "Carolina Heelsplitter." DNR. [http://www.dnr.sc.gov/cwcs/pdf/CarolinaHeelsplitter.pdf] .

* Fridell, John A.. "Carolina Heelsplitter in North Carolina." U.S. Fish and Wildlife Services. 2003. U.S. Fish and Wildlife Services. 8 Apr 2008 [http://www.fws.gov/nc-es/mussel/carolheel.html] .

* Ward, Sara . Augspurger, Tom. Dwyer, F. James. Kane, Cindy. Ingersoll, Christopher G. "Environmental Toxicology and Chemistry." SETAC Journals Online. 2007. Society of Environmental Toxicology and Chemistry. [http://www.setacjournals.org] .

* G. Booy, R. J. J. Hendriks, M. J. M. Smulders, J. M. Van Groenendael, B. Vosman (2000) Genetic Diversity and the Survival of Populations Plant Biology 2

* John FridellUS Fish and Wildlife Service

* "Species Information and Status." North Carolina Mussel Atlas. North Carolina Wildlife. [http://www.ncwildlife.org/pg07_WildlifeSpeciesCon/pg7b1a1_4.htm] .

* "Discover Goose Creek and the Carolina Heelsplitter." North Carolina Wildlife. North Carolina Wildlife Resources Commission. [http://www.ncwildlife.com/pg07_WildlifeSpeciesCon/documents/Educators_06.pdf]

* "Endangered and Threatened Wildlife and Plants; 5-Year Review of 19 Southeastern Species." Species Profile. 28 July 2006. U.S. Fish and Wildlife Service. [http://ecos.fws.gov/speciesProfile/SpeciesReport.do?spcode=F02L] .