Cyclonaias tuberculata 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Bivalvia Unionoida Unionidae

Scientific Name: Cyclonaias tuberculata Rafinesque, 1820
Common Name(s):
English Purple Wartyback

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2017
Date Assessed: 2015-06-10
Assessor(s): Woolnough, D. & Bogan, A.E.
Reviewer(s): Seddon, M.B. & Ormes, M.
Contributor(s): Cordeiro, J.
This species is of conservation concern in the northern parts of its range but is more stable in the southern reaches in Virginia, Kentucky, Tennessee, and Alabama. In parts of the range (Mississippi River and its tributaries) the Zebra Mussel (Dreissena polymorpha) started impacting the species in the 1990s and has caused further declines 25-30%, however it is not certain that these would exceed the 30% declines over three generations (30-60 years). Hence it is listed as Near Threatened due to declining population size and population abundance, declining area of occupancy and loss of subpopulations in the northern part of its extent of occurrence (EOO) as well as considering that over the rest of its EOO the habitat quality is continuing to decline due to pollution and channel management with an impact on those subpopulations. Further research and monitoring is required to evaluate whether the species may qualify as Vulnerable using criterion A in the future.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This large freshwater mussel species is widespread in the Interior and Great Lakes basins, North America (Graf and Cummings, Mussel-P, 2016).

In Canada, it is found in Ontario where it occurs in the Grand and Thames Rivers (Metcalfe-Smith and Cudmore-Vokey 2004).

In the United States, it is found in the Lake St. Clair drainage, the Mississippi River basin from southern Minnesota south to Arkansas, and from the Ohio River drainage in western Pennsylvania (historically) west to eastern Oklahoma (Williams et al. 2008). It is widespread in the Cumberland River drainage and is found throughout the Tennessee River drainage in Alabama, Kentucky, Tennessee, and Virginia (Parmalee and Bogan 1998, Williams et al. 2008).
Countries occurrence:
Canada (Ontario); United States (Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota, Mississippi, Missouri, North Carolina, Ohio, Pennsylvania - Possibly Extinct, South Dakota - Possibly Extinct, Tennessee, Virginia, West Virginia, Wisconsin)
Additional data:
Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:1930630
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is of conservation concern in the northern parts of its range, but is stable in the southern reaches (Williams et al. 2008). It is considered widespread and common in the New River drainages in Virginia (Pinder et al. 2002) and it is widely distributed, but sporadic in the Tennessee and Cumberland drainages in Kentucky, Tennessee, and Alabama (Cicerello and Schuster 2003, Parmalee and Bogan 1998, Williams et al. 2008, Jones et al. 2014).

It has declined in the northern part of the range. Surveys at three sites on the Thames River (Ontario) found only seven live individuals of this species at two sites (out of total of 626 live individuals, representing 16 different species across three sites) (Marson et al. 2012).

In Minnesota, past surveys and shell records indicate that the Purple Wartyback was once widely distributed in the Mississippi River below St. Anthony Falls and in the Minnesota and St. Croix Rivers, although it was not found in large numbers anywhere (Dawley 1947, van der Schalie and van der Schalie 1950). It is gone from the Minnesota River, but is still locally common in the St. Croix River drainage (Sietman 2003).

In Illinois, it is present in only three of the 12 drainages where it formally occurred (Cummings and Mayer 1997), including the mainstem Kankakee River, where it was  considered historically widespread. The Kankakee River drainage has been well-surveyed, with 40 species known historically. A survey of the entire drainage in 2010 found 28 live individuals at four sites (1.7% of the total number of live individuals representing 27 species) and smaller survey in 2012 found 11 live individuals at two sites (about 5% of the total number of live individuals representing 18 different species) (Price et al. 2012, Cummings and Tiemann 2013).

Although it had disappeared from much of the Huron River in Michigan by 1975, surveys in 1986 revealed that the Purple Wartyback had re-established itself in portions of the river where it had disappeared. This partial recovery was attributed to improvements in water quality between 1975 and 1986 (Cordeiro 2009).

In Indiana, only weathered shells have been found in streams in Tippecanoe County (in 1987 and 2001) (Myers-Kinzie et al. 2001).

It is extinct in Pennsylvania and is believed to be extinct in South Dakota (Cordeiro 2009).

It was found at a prehistoric site in Bayou Bartholomew, Arkansas in 2013, but has not been recorded from here in any modern surveys (Peacock et al. 2013).
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species typically inhabits a gravel/mud bottom, usually in areas of current at depths of less than two to up to 20 feet. Different forms inhabit medium-sized to small streams or in the main channel of large rivers (Parmalee and Bogan, 1998).
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):10-20

Use and Trade [top]

Use and Trade: This species was used for the pearl and button industry; it has a thick shell with purple nacre.

Threats [top]

Major Threat(s): The viability of remaining Purple Wartyback populations is jeopardized by the continuing decline in habitat conditions on the Mississippi, associated with its management as a navigation canal, and with non-point and point source water and sediment pollution. Dams, channelization, and dredging increase siltation, physically alter habitat conditions, and block the movement of fish hosts. In Illinois the The Purple Wartyback is also being impacted by the infestation of non-native Zebra Mussels (Dreissena polymorpha) in the Mississippi River and its tributaries. Zebra Mussels can attach themselves in large numbers to the shells of native mussels, eventually causing death by suffocation. If the effects of these factors cannot be mitigated, the Purple Wartyback may become endangered in the future.

Conservation Actions [top]

Conservation Actions: A 10-year statewide mussel survey initiated by the Minnesota DNR in 1999 resulted in a better understanding of the Purple Wartyback's ecology and current status in Minnesota. It is listed as a threatened species in the states of Illinois, Minnesota and Michigan.

The species was considered as Near Threatened in the early IUCN assessments (Bogan, pers. comm., 1995), as it was uncertain whether it met the thresholds for 20% decline over 3 generations for Vulnerable (Seddon, pers. comm, 2016).

Citation: Woolnough, D. & Bogan, A.E. 2017. Cyclonaias tuberculata. The IUCN Red List of Threatened Species 2017: e.T6018A62905357. . Downloaded on 22 July 2018.
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