The Tar River spiny mussel or Tar River spinymussel (''Elliptio steinstansana'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

freshwater mussel Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs ...

in the family

Unionidae The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is at its most diverse ...

, the river mussels. This species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. This species is endemic to North Carolina in the United States. It is expected to become extinct without significant human intervention. Under the

Endangered Species Act The Endangered Species Act of 1973 (ESA or "The Act"; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of ec ...

, this species is listed as

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

in the United States.

Description

Tar River spinymussels are a shade of yellow/brown when young but as they grow they become darker brown. These mussels earn their name from the row of spines that run on the posterior ridge of their shells, also known as valves . Each of the valves on the Tar River spinymussels can have up to 6 spines. The larger Tar River spinymussels don’t grow larger than roughly 5.5 cm (2.2 in).

Life History

The female spinymussels’ time of

gravidity In biology and human medicine, gravidity and parity are the number of times a woman is or has been pregnant (gravidity) and carried the pregnancies to a viable gestational age (parity). These terms are usually coupled, sometimes with additional t ...

runs from early April to mid-July. At the end of the gravid period the females release conglutinates into the water. Conglutinates are packets of

glochidia The glochidium (plural glochidia) is a microscopic larval stage of some freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels. These larvae are ...

. The fact that females release conglutinates multiple times during one brooding season makes the Tar River spinymussel

iteroparous Semelparity and iteroparity are two contrasting reproductive strategies available to living organisms. A species is considered semelparous if it is characterized by a single reproductive episode before death, and iteroparous if it is characteri ...

. The white shiner, the pinewoods shiner, and the bluehead chub are fish species that serve as the

hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman *Michel Host ( ...

for glochidia development. Temperature influences the amount of time during which the glochidia are attached on their host species. Studies have shown that warmer temperatures cause a shorter attachment time. Tar river spinymussels grow at a rate that ranges from 0.7-1.4mm/year. The closely related and also endangered James River spinymussel has a comparable life history. One study indicated that gravid James River spinymussels can release between 90 and 168 conglutinates. Juvenile Tar River spinymussels are about 4-10mm (0.16-0.39 inches) long.

Ecology

Diet

Tar River spinymussels, like many other mussels, are

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

s. They eat

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

, and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...

s by drawing in water. This type of feeding helps purify the water around them.

Behavior

The Tar River spinymussel, makes conglutinates which are filled with

, the

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e of a mussel. These conglutinates are made to attract its host. Many

minnow Minnow is the common name for a number of species of small freshwater fish, belonging to several genera of the families Cyprinidae and Leuciscidae. They are also known in Ireland as pinkeens. Smaller fish in the subfamily Leusciscidae are co ...

species try to eat these conglutinates which make them a known

host species In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

to the Tar River spinymussel glochidia. The glochidia then attaches to the host and after it has developed, will detach. When this species reproduces, females of the Tar River spinymussel can release up to four to five times the amount of conglutinates.

Habitat

The range of the Tar River spinymussel is very restricted which indicates that the suitable

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

for this species is limited. In the

Tar River The Tar River is a river that is approximately long, in northeast North Carolina flowing generally southeast to an estuary of Pamlico Sound. The Tar River becomes the tidal Pamlico River once it underpasses the U.S. Highway 17 Bridge in Washin ...

basin, the Tar River spinymussels exists in small population fragments while in the

Neuse River The Neuse River ( , Tuscarora: Neyuherú·kęʔkì·nęʔ) is a river rising in the Piedmont of North Carolina and emptying into Pamlico Sound below New Bern. Its total length is approximately , making it the longest river entirely contained in No ...

basin, there is much less of the species found. The Tar River spinymussel is mostly found in loose beds of coarse sand and gravel. They are found in areas that are wooded near streams. The spinymussel lives in water that is fast-flowing and of good quality, with less runoff and

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...

compared to the rest of the water system.

Range

This species is found in North Carolina. When the recovery plan was introduced, the three main populations of Tar River spinymussel were found in the main part of Tar River and in Swift Creek. The mainstream part of the Tar River contains two small populations while Swift Creek contains one larger population. All three of these populations are known to be able to reproduce. The population size of the Tar River spinymussel is estimated to be around 100-500.

Conservation

Population Size

Surveys done by the North Carolina Wildlife Resources Commission from 2014-2020 found only 11 individuals over the course of high-sampling efforts. This indicates that the population is still on the decline. There are currently fewer than 5 populations of Tar River spinymussels. These populations have low densities and are not connected geographically. Although surveys have recorded very few individuals it is possible that several thousands of Tar River spinymussels are still living. Although the historic population size of this species is uncertain, the historic range could have supported much larger populations.

Past and Current Geographical Distribution

The Tar River spinymussel is

to the Tar and Neuse Rivers both currently and historically. Before this area was settled in the 1700s, it is likely that this species occurred in many large waterways within the Tar and Neuse river basins. The Shocco creek, Tar, and Neuse river populations may already be

locally extinct Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...

. The Sandy creek, fishing creek, and little river populations still exist but are very small. The current populations suffer isolation from one another.

Major Threats

Sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...

: Increased amounts of

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

entering streams and rivers damage the

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...

of the habitat Tar River spinymussel occupies. Suspended sediment has the potential to clog the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s of freshwater mussels as well as changing the makeup of the sediments on the

riverbed A stream bed or streambed is the bottom of a stream or river (bathymetry) or the physical confine of the normal water flow ( channel). The lateral confines or channel margins are known as the stream banks or river banks, during all but flood ...

. Additionally, more suspended sediment leads to less light penetrating the water column which decreases

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

abundance. Without sufficient phytoplankton, the mussels lose a large part of their food source. Runoff water: High amounts of water running off of nearby non-penetrable surfaces have destabilized the stream and river banks where the Tar River spinymussel resides. Runoff water from

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

, residence, and

construction sites Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and come ...

contain chemical pollutants that are a major threat to the extant populations.

Pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...

in particular was implicated in the death of many individuals in the Tar River during a single event in 1990. Timbering operations: Timbering and

deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...

projects that operate within the Tar and Neuse river basins allow woody debris to enter the waterways and degrade the habitat of the spinymussels. Reducing the number of large trees that maintain the stability of the stream and river banks degrades the spinymussel’s habitat. Wastewater Mismanagement: Wastewater management facilities along the Tar River have histories of violating regulations controlling effluent

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

from their sites. Wastewater effluent can introduce toxic chemicals, diseases, and

microplastic Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a v ...

pollutants into the habitat of Tar River spinymussels.

Listing under the ESA

The Tar River spinymussel was listed as

on June 27, 1985.

Five-Year Review

The 5 year review for the Tar River spinymussel was initiated in the Federal Registrar on June 20, 2019. Its purpose was to provide information to decide whether this species should continue to be protected under the Endangered Species Act. It includes listing history, review history, population distribution, and factors that have been threatening the population. To determine the listing for the Tar River spinymussel, threats were examined. These threats included habitat change, overutilization, disease and

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

, and

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

. When the spinymussels were tracked, only 11 wild mussels were found. These extremely low numbers suggest that this species has been declining. Declining numbers as well as the previous threats mentioned indicate that the Tar River spinymussel still meets the definition of endangered. The 5 year review concludes that this species should continue to receive protection under the Endangered Species Act. The 5 year review also mentions the recovery plan and gives recommendations to promote recovery of the Tar River spinymussel. These recommendations focus on providing a

reintroduction Species reintroduction is the deliberate release of a species into the wild, from captivity or other areas where the organism is capable of survival. The goal of species reintroduction is to establish a healthy, genetically diverse, self-sustainin ...

program, decreasing threats, and

habitat restoration Restoration ecology is the scientific study supporting the practice of ecological restoration, which is the practice of renewing and restoring degraded, damaged, or destroyed ecosystems and habitats in the environment by active human interrupt ...

Species Status Assessment

The Species Status Assessment is currently unavailable for the Tar River spinymussel.

Recovery Plan

The recovery plan was first established in 1985, revised in 1992, and amended in 2019. In 1985, the reasons for listing included habitat modification/destruction, over-utilization, disease/predation, lack of regulatory mechanisms, and

exotic species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

. The 1985 plan states that there is no need for

critical habitat Critical habitat is a habitat area essential to the conservation of a listed species, though the area need not actually be occupied by the species at the time it is designated. This is a specific term and designation within the U.S. Endangered Spec ...

designation, and this has yet to be updated. For the Tar River spinymussel to be moved from endangered to

threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensat ...

, the 1992 plan listed four criteria: # Evidence of reproduction in all populations # At least two new populations are discovered # All populations and their habitats are protected against future threats # All population sizes remain stable or increase in a period of fifteen to twenty years. In 2019, these criteria were amended in three ways: # At least seven sub-population sizes must increase or remain stable # The

spatial distribution A spatial distribution in statistics is the arrangement of a phenomenon across the Earth's surface and a graphical display of such an arrangement is an important tool in geographical and environmental statistics. A graphical display of a spatial di ...

of the seven sub-populations must include one sub-population in each of the Tar and Neuse river basins # The threats are managed so that the species will remain viable into the foreseeable future Some of the actions provided to meet these criteria include using existing legislation, getting support via educational programs, as well as searching for and monitoring populations.

References

External links

*USFWS
''Elliptio steinstansana'' Recovery Plan.
May 1992. {{DEFAULTSORT:Tar_River_spinymussel_(Elliptio steinstansana) Endemic fauna of North Carolina Molluscs described in 1983 Elliptio ESA endangered species Taxonomy articles created by Polbot Taxobox binomials not recognized by IUCN