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Spectaclecase

Cumberlandia monodonta

Summary 2

The spectacle case pearly mussel or spectacle case (Cumberlandia monodonta) is a species of bivalve in the Margaritiferidae family. It is endemic to the United States.

Diagnostic description 3

Only two shells are similar to this species in its historical range, Elliptio dilatata (Rafinesque, 1820) and Ligumia recta (Lamarck, 1819). Both of the species always have well-developed hinge dentition, often have purple nacres (sometimes white, pinkish or orangish), have periostraca which may be rayed (distinctly or obscurly), and are pointed posteriorly (female L. recta are truncated posteriorly, but still have a point at the dorsal-posterior junction). Ligumia recta is never arcuate. Dry Cumberlandia shells tend to be brittle, crack, and posterior ends break-off. Butler (2003) and Oesch (1995) list key characters as large size, elongate shape, arcuate ventral margin, dark coloration, roughened surface, poorly developed teeth, and white nacre.

Distribution 4

Global Range: (5000-20,000 square km (about 2000-8000 square miles)) Historically, this species occurred throughout much of the Mississippi River system with the exception of the upper Missouri River system, uppermost Ohio River system, Cumberland and Tennessee River systems, and some tributaries in the lower Mississippi region of Arkansas. Historically, it is known from 45 streams in 15 states including: upper Mississippi River system (Mississippi River); lower Missouri River system (Missouri River?); Ohio River system (Ohio River); Cumberland River system (Cumberland River); Tennessee River system (Tennessee River); and lower Mississippi River system (Mulberry, Ouachita Rivers) (Butler, 2003; USFWS, 2003). Ahlstedt et al. (2004) recently reported sporadic occurrences (two recent) from the Duck River in a reach less than 30 miles long.

Ecology 5

This species often has been found in small, apparently even-aged clumps of individuals, indicating that they excysted from the glochidial host simultaneously. No ecological studies have been conducted on this species. Available data is derived from haphazard observations made during species surveys.

Habitat 6

Habitat Type: Freshwater

Comments: The spectaclecase occurs in large rivers and is a habitat-specialist, relative to other mussel species. Baird (2000) noted its occurrence on outside river bends below bluff lines. It seems to most often inhabit riverine microhabitats that are sheltered from the main force of current. Utterback's (1915) record of this species in the Northwest Missouri Lakes is puzzling, but may refer to seasonally flooded oxbow lakes along the Missouri River. It occurs in substrates from mud and sand to gravel, cobble, and boulders in relatively shallow riffles and shoals with slow to swift current (Buchanan, 1980; Parmalee and Bogan, 1998; Baird, 2000). According to Stansbery (1967), spectaclecase is usually found in firm mud between large rocks in quiet water very near the interface with swift currents. Specimens have also been reported in tree stumps, root masses, and in beds of rooted vegetation (Stansbery, 1967; Oesch, 1995). Similar to other margaritiferids, spectaclecase tend to be aggregated (Gordon and Layzer, 1989), particularly under slab boulders or bedrock shelves (Call, 1900; Hinkley, 1906; Buchanan, 1980; Parmalee and Bogan, 1998; Baird, 2000), where they are protected from the current. Unlike most species that move about to some degree, the spectaclecase may seldom, if ever, move except to burrow deeper; they may die from stranding during droughts (Oesch, 1995).

Habitat and ecology 7

Habitat and Ecology

The Spectaclecase occurs in large rivers and is a habitat-specialist, relative to other mussel species.This species is confined to flowing water systems only (USFWS 2003).Baird (2000) noted its occurrence on outside river bends below bluff lines. It seems to most often inhabit riverine microhabitats that are sheltered from the main force of current. Utterback's (1915) record of this species in the Northwest Missouri Lakes is puzzling, but may refer to seasonally flooded oxbow lakes along the Missouri River. It occurs in substrates from mud and sand to gravel, cobble, and boulders in relatively shallow riffles and shoals with slow to swift current (Buchanan 1980, Parmalee and Bogan 1998, Baird 2000). According to Stansbery (1967), the Spectaclecase is usually found in firm mud between large rocks in quiet water very near the interface with swift currents. Specimens have also been reported in tree stumps, root masses, and in beds of rooted vegetation (Stansbery 1967, Oesch 1995). Similar to other margaritiferids, the Spectaclecase tends to be found in aggregations (Gordon and Layzer 1989), particularly under slab boulders or bedrock shelves (Call 1900, Hinkley 1906, Buchanan 1980, Parmalee and Bogan 1998, Baird 2000), where they are protected from the current. Unlike most species that move about to some degree, the Spectaclecase may seldom, if ever, move except to burrow deeper; they may die from stranding during droughts (Oesch 1995).

The life history of this speciesin the Gasconade and Meramec rivers, Missouri, was reported by Baird (2000). That population had a 1:1 sex ratio, no sexual dimorphism in shell morphology and no hermaphroditic individuals. However, occasional hermaphrodites have been reported (van der Schalie 1966). The age at sexual maturity in the Gasconade and Meramec rivers is four to five years for males and five to seven years for females, but inference from growth rate suggests major investment in reproduction may not occur until after about 10 years. Based on maximum ages recorded by Baird (2000) of 56 years, this would put the generation length (average age of parent) at 30-33 years (and three generations at 90-100 years). This species is a long-term brooder. In the Gasconade and Meramec rivers, females brooded eggs between September and December, and mature glochidia in April and May. Conglutinates are white, branched and feathery. Fecundity was reported to range from approximately 2,000,000 to more than 9,000,000 (Baird 2000,Williamset al. 2008). It has been suggested that the species may produce two broods per year (Howard 1915, Gordon and Smith 1990), but Baird (2000) reported no evidence of biannual reproduction.

Baird (2000) reported no successful transformations of glochidia in laboratory host fish trials. However, natural infestations of the species were found on Moxostoma macrolepidotum (Shorthead Redhorse, Catostomidae) and Hybopsis amblops (Bigeye Chub, Cyprinidae) from the Meramec River, Missouri (Baird 2000,Williams et al. 2008).

Systems
  • Freshwater

Iucn red list assessment 8


Red List Category
EN
Endangered

Red List Criteria
A2ac

Version
3.1

Year Assessed
2012

Assessor/s
Cummings, K. & Cordeiro, J.

Reviewer/s
Bohm, M., Seddon, M. & Collen, B.

Contributor/s
Richman, N., Dyer, E., Soulsby, A.-M., Whitton, F., McGuinness, S., Kasthala, G., Milligan, HT, De Silva, R., Herdson, R., Thorley, J., McMillan, K., Collins, A., Duncan, C. & Offord, S.

Justification
Cumberlandia monodonta has been assessed as Endangered under A2ac, because of estimated and, in parts of its range, observed declines in individuals, populations and area of occupancy of between 30-70% over the past century. Assuming that the average number provides us with a good estimate of decline, and given the long generation length of this species, a 50% decline over the past three generations is inferred. The species is now extirpated from several U.S. states (Indiana, Kansas, Nebraska, Ohio) and many of the remaining populations have poor or no viability. The species has largely been reduced to a relatively few disjunct sites, some of which may not be capable of reproduction either through loss of fish hosts or adverse environmental conditions (e.g., hypolimnetic release from reservoirs). Only the Gasconade and Meramec Rivers of Missouri and perhaps also in the Upper Clinch River, Tennessee are fairly stable for now, with the remaining populations in decline. Further research and protection is required in order to offer this species adequate conservation protection.

In 1996 the species was considered 'Near Threatened' in a review by Bogan and Seddon (Seddon, pers. comm., 2012), on grounds of population loss over the region (see 1996 & 2000 Red List). However this more comprehensive review provides more data on range and decline rates allowing review and confirmation of higher threat status.

History
  • 2000
    Lower Risk/near threatened (LR/nt)
  • 1996
    Lower Risk/near threatened (LR/nt)
  • 1994
    Indeterminate (I)
  • 1990
    Indeterminate (I)
  • 1988
    Indeterminate (I)
  • 1986
    Indeterminate (I)

Nature serve conservation status 9

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Area of occupancy of this species has been drastically reduced (near 50%) with continuing decline of populations. Range extent has also been reduced as the species is extirpated from several U.S. states (Indiana, Kansas, Nebraska, Ohio) and many of the remaining populations have poor or no viability. The species has largely been reduced to a relatively few disjunct sites, some of which may not be capable of reproduction either through loss of fish hosts or adverse environmental conditions (e.g., hypolimnetic release from reservoirs). Only the Gasconade and Meramec Rivers of Missouri and perhaps also in the Upper Clinch River, Tennessee are fairly stable for now with the remaning populations in decline.

Intrinsic Vulnerability: Highly to moderately vulnerable.

Comments: The likelihood that some populations of the spectaclecase are below the effective population size necessary to adapt to environmental change and persist in the long-term seems high. Many small spectaclecase populations may be reproducing at levels too low to persist despite high adult survival. These populations may also be too isolated to be sustained by recruits from other populations. This species was widespread throughout much of the upper two-thirds of the Mississippi River system and in several tributary systems, and there were likely no or few natural barriers to prevent migration (via fish hosts) among suitable habitats. Construction of dams, primarily during the first half of the 20th century, destroyed spectaclecase populations and isolated others (USFWS, 2003).

Environmental Specificity: Moderate. Generalist or community with some key requirements scarce.

Comments: This species is confined to flowing water systems only (USFWS, 2003).

Sources and Credits

  1. (c) USFWSmidwest, some rights reserved (CC BY), http://commons.wikimedia.org/wiki/File:Cumberlandia_monodonta.jpg
  2. Adapted by rkkessler from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Cumberlandia_monodonta
  3. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28949311
  4. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28949305
  5. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28949313
  6. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28949315
  7. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34408111
  8. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34408108
  9. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28949298

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