''Obovaria retusa'' is a rare species of

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. Its common names include golf stick pearly mussel This mussel was native to

Alabama (We dare defend our rights) , anthem = "Alabama (state song), Alabama" , image_map = Alabama in United States.svg , seat = Montgomery, Alabama, Montgomery , LargestCity = Huntsville, Alabama, Huntsville , LargestCounty = Baldwin County, Al ...

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolita ...

Indiana Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th s ...

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia to ...

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

, and

West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...

. By 1991 it was thought that there were about five populations remaining in Kentucky, Tennessee, and West Virginia. It is now thought to be

extirpated 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 ...

from West Virginia, as the population there was a misidentification. Only a few specimens of the species have been observed recently. If any viable populations remain, they will be located in the

Green River Green River may refer to: Rivers Canada * Green River (British Columbia), a tributary of the Lillooet River *Green River, a tributary of the Saint John River, also known by its French name of Rivière Verte *Green River (Ontario), a tributary of ...

of Kentucky.

General Summary

The Ring Pink mussel (Obovaria retusa) is also referred to as the “golf stick pearly mussel” or “Ring Pink.”Biggins, Richard G. “Ring Pink Mussel Recovery Plan.” Ecos.fws.gov, U.S. Fish and Wildlife Service, 25 Mar. 1991, https://ecos.fws.gov/docs/recovery_plan/910325.pdf. Ring Pink mussels are

freshwater bivalves 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 ...

. They are in the river mussel family

. Ring Pink mussels are native to the eastern and southeastern regions of the United States. They are currently found in Alabama, Kentucky, and Tennessee. The U.S. Fish and Wildlife Services listed the Ring Pink mussel as an endangered species 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 ...

in 1989. The species is still listed as endangered.Koch, Leroy, et al. “Ring Pink Obovaria Retusa (Lamarck, 1819) 5-Year Review: Summary and Evaluation .” Federal Register, U.S. Fish and Wildlife Service, 25 Sept. 2019, https://ecos.fws.gov/docs/tess/species_nonpublish/2870.pdf

Morphological Description

The Ring Pink mussel was first described by the french naturalist Jean-Baptise Lamarck in 1819. This mussel has a medium to large shell. The shapes of this shell can range from oval to square. The exterior of the shell ( periostracum) does not have rays and has a yellow-green to brown color. Usually, older individuals are darker brown or black. The inner layer of the shell (

nacre Nacre ( , ), also known as mother of pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer; it is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is f ...

) has a salmon to deep purple color and a white border.

Life History

General

information supplements the current knowledge on the Ring Pink mussel. The Ring Pink mussel’s life cycle and history are not well known. For freshwater mussels, males discharge their sperm into the water column. Females take their sperm in through their gills to fertilize the eggs. In typical freshwater mussel life cycles, the larvae develop into a life stage called

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 ...

. Pregnant females release glochidia from their gills. After release, these glochidia attach to the gills or scales of freshwater fish. Once attached to the fish, the larvae act as parasites for weeks to months. It is unknown if the Ring Pink mussel utilizes a specific fish species or is more generalist in their attachment. This

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

attachment to the host fish determines their population distribution. During this time as a parasite they metamorphosize into juvenile mussels. Afterwards, they detach from their fish host. The juvenile mussels sink to the

benthos Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.Ortmann, A. E. 1909. The breeding season of Unionidae in Pennsylvania. Nautilus, 22(9):91-95; 22(10):99-103. Ring Pink mussels pregnant with

have been observed in late August.Ortmann, A. E. 1912. Notes upon the families and genera of the naiades. Annals Carnegie Mus., 8:222-365. Ring Pink

have been described as “rather large and hookless”. Overall, Ring Pink mussels and other freshwater mussels are long-lived organisms. They exhibit

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

reproduction and reach sexual maturity at a late stage. They have a low frequency of successful reproduction events.

Ecology

Diet

The Ring Pink mussel’s specific diet is unknown. Its diet likely does not differ from the diet of other freshwater mussels. Freshwater mussels’ diets often comprise

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

, diatoms,

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 ...

, and

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

.Churchill, E. P., Jr., and S. I. Lewis. 1924. Food and feeding in freshwater mussels. Bull. U.S. Bur. Fish. 39:439-471

Behavior

Little is known about the Ring Pink’s reproductive behavior. Ring Pink mussel mating is thought to resemble that of other freshwater mussels. Freshwater mussels typically exhibit burrowing behavior in juvenile stages. See Life History section for more information. Since the Ring Pink mussel is a rare species, there have been few reports of its behavior in the wild.

Habitat

The Ring Pink mussel is found in medium to large rivers. They inhabit the silt, sand, and gravel substrate of these rivers. The Ring Pink does not frequent habitats deeper than about one meter.

Range

Historically, the Ring Pink mussel is native to the Ohio River and its

tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage b ...

in Pennsylvania, West Virginia, Ohio, Indiana, Illinois, Kentucky, Tennessee, and Alabama. Its range has decreased due to damming. The Ring Pink mussel is currently found or believed to be found in Alabama, Tennessee, and Kentucky.

Conservation

Population Size

Construction of dams on large rivers has caused declining numbers of the Ring Pink. In the Ring Pink mussel 1991 recovery plan, five known populations of Ring Pink mussels were reported. However, few sightings of the species have been noted since the early 1990s.Mussel Life Cycle - Minnesota State University, Mankato. https://mrbdc.mnsu.edu/sites/mrbdc.mnsu.edu/files/public/pdf/askexpert/mussel_lifecycle.pdf. In the past 15 years, only two live Ring Pink individuals have been observed. Both sightings were in the Green River in Kentucky. It is hard to find the mussel through typical surveying methods, so small populations of the Ring Pink may still exist. The 1991 Ring Pink recovery plan noted that the five populations in existence were old and most likely non-reproducing. A recent review by the U.S. Fish and Wildlife Services asserts that no viable populations currently exist.Koch, Leroy, et al. “Ring Pink Obovaria Retusa (Lamarck, 1819) 5-Year Review: Summary and Evaluation .” Federal Register, U.S. Fish and Wildlife Service, 27 Apr. 2011 https://ecos.fws.gov/docs/tess/species_nonpublish/1732.pdf. Studies have shown that decreased densities of freshwater mussels may lead to decreased fertilization and reproduction, possibly explaining the sudden drop in species numbers. Seeing that there are no reproducing populations, it is unlikely that population size will increase.

Past and Current Geographical Distribution

In the past, the Ring Pink mussel was widely distributed among the Ohio River and its tributaries. These rivers span Pennsylvania, West Virginia, Ohio, Illinois, Indiana, Kentucky, Tennessee, and Alabama. By 1991, only five populations of the Ring Rink mussel were known and occurred in Kentucky, Tennessee, and West Virginia. Since 1998, there have only been four sightings of the Ring Pink at the Green River in Kentucky. As of 2019, it is believed that a small population of Ring Pinks in the Green River is the only population in existence. There is some speculation that Ring Pink individuals may occur in the Cumberland and Tennessee Rivers as well.

Major Threats and Human Impact

The Ring Pink mussel is thought to be sensitive to habitat degradation. In the 1991 Ring Pink Recovery Plan, the U.S. Fish and Wildlife Services cite dam construction as a major cause of Ring Pink endangerment. Dam construction reduces the availability of preferred gravel and sand habitat for the Ring Pink. Dams also disrupt the life cycle of the Ring Pink mussel by limiting the availability of host fish for Ring Pink larvae. Gravel dredging and channel maintenance also contribute to habitat loss for the Ring Pink mussel. Besides habitat destruction, commercial mussel fishing also poses a threat to the Ring Pink mussel. The mussel is sometimes taken during commercial mussel fishing of other species.

Listing Under the ESA

As of September 29, 1989, the species is listed as endangered under the Endangered Species Act. It was also listed as a small experimental, non-essential population established on October 15, 2007 in some portions of the

French Broad River The French Broad River is a river in the U.S. states of North Carolina and Tennessee. It flows from near the town of Rosman in Transylvania County, North Carolina, into Tennessee, where its confluence with the Holston River at Knoxville form ...

and

Holston River The Holston River is a river that flows from Kingsport, Tennessee, to Knoxville, Tennessee. Along with its three major forks (North Fork, Middle Fork and South Fork), it comprises a major river system that drains much of northeastern Tennessee ...

in Tennessee.

5-Year Review

The U.S. Fish and Wildlife Services has completed and published two 5-year reviews. These reviews determine species status and recovery achievements. The U.S. Fish and Wildlife Services publicly announced a review of the Ring Pink Mussel on November 6, 1991. This document provided no in-depth evaluation of species’ recovery,Koch, Leroy, et al. “Ring Pink Obovaria Retusa (Lamarck, 1819) 5-Year Review: Summary and Evaluation .” Federal Register, U.S. Fish and Wildlife Service, 27 Apr. 2011 https://ecos.fws.gov/docs/tess/species_nonpublish/1732.pdf. and no 5-year review was published in the decade after this notification. Another review was published in 2011. The review conducted a five-factor analysis of threats to the Ring Pink habitat. Habitat threats include overutilization, disease, predation, regulations, and other anthropogenic and natural factors affecting its existence. Only three individuals had been found between 1998 and 2011. Based on these results, the 2011 5-year review asserted that the Ring Pink should remain an endangered species. Another public notice of a 5-year review was announced on June 20, 2017 in the Federal Register. This review was published in 2019. This review presented a similar five-factor analysis and stated no need for change in listing. Both reviews assert there is a high threat to the Ring Pink species. Experts consider recovery potential as low. See “Recovery Plan” section for more information on recommendations for future action.

Species Status Assessment

No Species Status Assessments are currently available for this species.Department of the Interior; Endangered and Threatened Wildlife and Plants; 5-Year Review of Listed Species; Proposed Rule 56 Fed. Reg. 215 (November 6, 1991).

Recovery Plan

The aim of the U.S. Fish and Wildlife Recovery Plan is to downlist the Ring Pink mussel from endangered to threatened. Total recovery is not thought to be possible. The downlisting date cannot be estimated at this time. Mussels do not reproduce until about age 5. More than 10 years are needed to document reproduction and assess viability. Experts must study the impact of commercial fisheries. Some river beaches may need to be declared mussel sanctuaries. Recommendations for future actions acknowledge the limited success in finding individuals. Experts could perform surveys in the Tennessee and Cumberland rivers to find sites with suitable habitat. One suggestion was to determine the fish host(s) of the Ring Pink and propagate the species. This way, propagated juveniles could be moved to areas with mussel assemblages. The Round Hickorynut, another mollusk that could be considered a potential proxy, is hosted by the sand darter. This may indicate that the Ring Pink’s host is Ammocrypta clara and/or Ammocrypta pellucida. Another suggestion is to begin studies in cryopreservation. This could preserve

gametes A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

and

, since it is challenging to induce natural reproduction.

Responsible Parties

Kentucky Ecological Services Field Office, National Park Service, U.S. Forest Service, Indiana Department of Natural Resources, Tennessee Valley Authority , Tennessee Wildlife Resources Agency , Tennessee Department of Conservation , Fish and Wildlife Enhancement, Illinois Department of Conservation, Kentucky Department of Fish and Wildlife Resources, Kentucky State Nature Preserves Commission, Virginia Department of Game and Inland Fisheries, Kentucky Department for Surface Mining Reclamation and Enforcement, US Office of Surface Mining Reclamation and Enforcement, West Virginia Department of Natural Resources, USFWS Regional Office 5, USFWS Regional Office 3, USFWS Regional Office 4

References

Molluscs of the United States

retusa ''Retusa'' is a genus of very small head-shield sea snails or barrel-bubble snails, marine gastropod mollusks in the family Retusidae.Bouchet, P.; Gofas, S. (2013). ''Retusa'' T. Brown, 1827. Accessed through: World Register of Marine Species at ...

Bivalves described in 1819 ESA endangered species Taxonomy articles created by Polbot {{Unionidae-stub