Discovery Guides Areas


Freshwater Mussels: Engineering Ecosystems One Shell at a Time
(Released August 2011)

  by Natalie Abram  


Key Citations




Resources News Articles
Historical Newspapers

News Articles

  1. Endangered invertebrates: The case for greater attention to invertebrate conservation

    Black, Scott Hoffman; Shepard, Matthew; Allen, Melody Mackey, Endangered Species Update, 03-01-2001

    Invertebrates eclipse all other forms of life on Earth, not only in sheer numbers, diversity, and biomass, but also in their importance to functioning ecosystems. Invertebrates perform vital services such as pollination, seed dispersal, and nutrient recycling. Although invertebrates are vitally important, they are often overlooked in management decisions, especially in management for endangered species. One indicator of the low emphasis on invertebrates is the lack of invertebrates included in both worldwide and US. endangered species programs. A review of current U.S. Endangered Species Act listings and policies show that this endangered species program is biased toward vertebrates We believe there is compelling evidence that agencies, scientists, conservationists, and land managers should do more to promote the conservation of imperiled invertebrates. We briefly outline the steps that need to be taken to protect invertebrates and detail butterfly farming and a pollinator protection campaign as two possible ways to protect and restore invertebrate diversity and habitat.

    For full-text documents see ProQuest's eLibrary


    Knight, Danielle, Global Information Network, 01-07-2002

    WASHINGTON, Jan. 7 (IPS) — Loss of habitat for flora and fauna in Canada, Mexico and the United States has caused a "widespread crisis" of shrinking of biodiversity throughout the region, an inter-governmental environmental body warned today.

    The remaining natural environments in the region are under enormous stress and have been fragmented, polluted, or damaged in other ways despite efforts to set aside protected areas, the North American Commission for Environmental Cooperation (CEC) said in a report to the three countries' governments.

    "Over the past few decades, the loss and alternation of habitat has become the main threat to biodiversity," said Janine Ferretti, executive director of the Montreal-based CEC, which was set up under the 1993 North American Free Trade Agreement (NAFTA) at the request of environmental groups.

    The report, "The North American Mosaic: A State of the Environment Report," was based on scientific papers prepared for the CEC by scholars and government experts in the three nations.

    Half of North America's most biologically diverse areas were severely degraded, said the report. At least 235 species of mammals, birds, reptiles and amphibians — including the Monarch Butterfly and Northern Codfish — were threatened.

    Freshwater species were especially at risk because physical barriers, including dams, prevented them from escaping to new ecosystems when their own habitat became destroyed or degraded.

    "The United States contains the world's greatest diversity of freshwater mussel species but more than 65 percent of these are threatened or extinct," said the report.

    For full-text documents see ProQuest's eLibrary

  3. Musseled out

    O Connell, Kim A, National Parks, 01-01-1997

    To THE CASUAL observer wading in a river or creek, mussels may be nothing more than rock-like objects. But these freshwater bivalves-considered indicator species-contain crucial information about river ecosystems. When mussels' numbers fall, a river's water quality could be in serious danger.

    Currently two-thirds of all freshwater mussels in the United States are at risk, according to a report released last summer by The Nature Conservancy The mollusks are the most rapidly dedining animal group in the country, and some scientists believe that one in ten species may have become extinct during this century alone. The federal endangered species list includes about two dozen species of mussels, with such colorful names as the Appalachian monkeyface pearlymussel, the orangefoot pimpleback pearlymussel, and the purple cat's paw pearlymussel.

    Many freshwater mussels reside in the waterways of the Midwest and the Southeast, including St. Croix National Scenic Riverway in Wisconsin, Ozark National Scenic Riverways in Missouri, and Big South Fork National River and Recreation Area in Tennessee and Kentucky. The decline of freshwater mussels largely can be attributed to human actions. Agricultural runoff as well as improper erosion-control practices and dredge-and-fill activities are major killers of mussels. Known as filter feeders, these shellfish require unsilted, free-flowing water to survive.

    Dams pose another threat by altering the flow of a river and preventing the migration of fish. Immature freshwater mussels must attach to a host fish species to complete their lifecycle. Without the host fish-which also helps to disperse the mussels—the young mollusks will die.

    Mussels also are suffering as a result of the inadvertent introduction of an aggressive, non-native cousin-the zebra mussel. No larger than a quarter, the Eurasian zebra mussel, believed to have arrived in this country by transatlantic ship sometime before 1988, has spread throughout the Great Lakes and the Mississippi River basin. If this expansion continues unchecked, native mussels of the Mississippi River, which contains more endemic species of mussels than any other river system, could be reduced by 50 percent within a decade.

    For full-text documents see ProQuest's eLibrary

Historical Newspapers
  1. MUSSELS TO BE SAVED; Federal and State Experts Propagate Pearl Makers. SPECIES IS NEAR EXTINCTION Investigation Extending Over Several Years Just Ended Proves That Valu- able Shellfish Can Be Saved and Grown Like Oysters — Work Is Begun at the Station at Fairport, Iowa.

    The Washington Post , Apr 28, 1912.

    Abstract (Summary) The threatened extinction in the upper Mississippi River and its tributaries of fresh-water mussels, whose shells have been taken in enormous numbers, both for the manufacture of pearl buttons and for the pearls which they occasionally contain, is ended. The United States and the State of Missouri will protect and breed them.

    Original Newspaper Image (PDF)

  2. MUSSEL HATCHING CHANGED; Fish Hosts Replaced by Artificial Nutrient Medium.

    New York Times , Sep 25, 1926.

    Abstract (Summary) On the basis of experiments which have been carried on for the last two years fishery experts are hopeful that the culture and propagation of freshwater mussels can in the future be accomplished through purely artificial means, thus dispensing with the use of fish which have heretofore formed the hosts for the young embryonic mussels while they passed through their parasitic stage of development.

    Original Newspaper Image (PDF)

  3. Those Endangered Species: What Good Are They?

    PETER STEINHART, Los Angeles Times , Jul 2, 1978.

    Abstract (Summary) The Tennessee state legislature, which only a few years ago was telling school teachers that Darwin's theory was nothing more than an interesting guess, is suddenly filled with "born again" evolutionists.

    Original Newspaper Image (PDF)

Taken from ProQuest's Historical Newspapers.


  1. Evaluation of diet, gametogenesis, and hermaphroditism in freshwater mussels (Bivalvia: Unionidae)

    by Henley, William F. Ph.D. Virginia Polytechnic Institute and State University, 2002.

    Abstract (Summary)
    To determine the effects of different algal diets on freshwater mussels, tissues of Elliptio complanata were sampled for physiological, somatic, and gametogenic condition from August 1999 to May 2000. Treatments included mussels fed Scenedesmus quadricauda (S), Neochloris oleoabundans (N), a no feed treatment (NF), and a reference group of mussels from the Nottoway River (NR), Virginia. The levels of protein and glucose differed among treatments (p < 0.0001), but glycogen and percentage tissue moisture did not (p > 0.17). Production of ripe and developing gametes differed significantly among treatments (p = 0.001), but stage of gamete development did not (p = 0.70). Lipid levels and muscle fiber areas of treatment groups differed significantly (p < 0.0001). Results of the feeding trial indicate that S. quadricauda is a suitable feed for E. complanata , but future experiments should identify algal species higher in carbohydrates for a mixed algal diet. To determine sex and stage of gametogenesis, tissue histological sections from gonads of Villosa iris and Utterbackia imbecillis were evaluated. Occurrences of oogenic, spermatogenic, and hermaphroditic tissues were summarized in frequency tables. Visceral sites from which similar tissues were collected from conspecific specimens were evaluated for gametogenic stage. Sex was accurately determined in the central, visceral portion V. iris and female regions of U. imbecillis ; and spermatogenic tissue was consistent in the dorsal-anterior areas of U. imbecillis . These areas also provided accurate determination of gamete stage in specimens. Reproductive asynchrony was observed among males and females (p < 0.02). Male regions of U. imbecillis showed gamete stage characterized by mature and developing spermatogenic tissue, while 2 groups of mussels were showed oogenic development characterized by mature oocytes and resorption of gametes. Male V. iris showed early gamete development without mature spermatozoa, and 2 groups of female V. iris showed mature and developing gametes and resorption of gametes. Protocols for biopsy tissue collection from selected visceral areas were developed for U. imbecillis and V. iris for sex determination and staging of gametogenesis. The application of this biopsy protocol should be considered population specific, and protocols appropriate for other populations and species should be developed with methods of this study.

    For full-text documents see ProQuest's Dissertations & Theses Database

  2. Host infection strategies determine dispersal abilities in freshwater mussels (Bivalvia: Unionidae)

    by Schwalb, Astrid Nadine. Ph.D. University of Guelph (Canada), 2010.

    Abstract (Summary)
    Unionid freshwater mussels are a highly imperiled group. Little is known about their dispersal, which is a complex process that depends on the transport of larvae (glochidia) and juveniles in the water column, and movement of their host fish during the mussels' parasitic stage. The hypothesis of this research was that specialization with respect to host infection strategy influences dispersal abilities. This was examined by comparing dispersal processes and early life history traits among Lampsilini mussels. I focused on Actinonaias ligamentina that broadcasts its glochidia and was therefore considered a "generalist", and Epioblasma triquetra , a "specialist" that captures its host between the valves. Release experiments with stained glochidia showed that glochidia of the generalist can travel in the water column considerable distances (up to 100 m in low flow conditions), whereas glochidia of the specialist can attach directly to the trapped fish. Transport distances of juvenile mussels of both species may extend over 10s of m as suggested by a combination of field and lab experiments, if turbulent flow conditions diminish the effect of lower release heights in the water column from the specialist's benthic hosts. Examination of host fish movements were based on a mark-recapture study and a literature review, which indicated that the specialist's host fish has significantly shorter movement distances (10s of m) than host fish of the generalist (100s of m to km).

    In addition, the conservation statuses of mussels in Ontario appear to be associated with the movement distances of their host fish. Overall, the generalist (broadcaster) has . considerably larger dispersal distances than the specialist (host capture), which is reflected in the findings that early life history traits relevant for dispersal differ considerably between broadcasting and host capture species. Other species that attract hosts with mimetic mantle flaps and packages of glochidia (conglutinates) fill positions between these extremes with respect to both dispersal abilities and early life history traits. This study demonstrates that dispersal distances can differ considerably among mussel species, but are predictable based on their ecology, which is a crucial first step to understand connectivity of populations and to develop sound conservation strategies.

    For full-text documents see ProQuest's Dissertations & Theses Database

  3. Investigations for the conservation and propagation of freshwater mussels

    by Owen, Christopher T. Ph.D. University of Louisville, 2009.

    Abstract (Summary)
    Freshwater mussels are the most imperiled freshwater fauna in North America. Species faced unregulated harvest during the 'ignorant extermination' periods where they were sought for their pearls and mother-of-pearl shells. Much of the native range of most species has dwindled due to the loss of habitat from impoundment by rivers and dams. Impoundment also impacted mussels by blocking the migration of many host fishes, as unionids are briefly parasitic on fish and thus dependent upon fishes for reproduction. Over 70% of all unionid taxa are deemed threatened, endangered or of special concern, and much of this loss of biodiversity can be embodied by E. O. Wilson's HIPPO concept. Conservation efforts to preserve and protect these species have been constrained due to the lack of understanding of the natural history of most species and currently consist of mitigating destabilizing impacts to existing populations and bolstering mussel populations in areas with critical mussel habitat through propagation. Muskrats are natural predators of all freshwater mussels and can severely impact already vulnerable populations, possibly reducing populations below the minimum number for successful reproduction (Alice effect). Muskrats appear to select mussels after developing a search image for particular prey-type. At our site, muskrats favored cube-shaped (inflated or swollen) animals, over compressed mussels of equal lengths, presumably because inflated individuals tend to have more edible soft tissues (or at least possess the appearance that they do). Muskrats were extremely efficient at finding cube shaped species that were found at extremely low densities in the live community, such as Quadrula metanevra. Muskrats also heavily favored the endangered Fanshell Pearlymussel, Cyprogenia stegaria, which was the number one favored prey item at our site. The majority of endangered unionids (measured from our site and museum specimens) fall within the same size and shape of the species favored in our study. Given the efficiency of muskrats at finding particular prey species, mitigation of predation pressure by locally trapping or relocating muskrats should be considered as part of mussel recovery programs. Mitigation may be necessary for successfully bolstering or establishing new populations with propagated juveniles released into critical mussel habitat.

    In vitro metamorphosis is such a propagation method. It facilitates culturing unionids without their host fish, and may be the only method of propagation for many endangered species for which the host fish is unknown. We investigated the components and protocol of the in vitro method to increase the efficacy of producing healthy juvenile mussels. Control of microbial contamination was the major impediment to successfully culturing most species. Microbial contamination is best controlled by minimizing the introduction of microbes into the culture dishes, changing the culture medium regularly and replenishing antibiotics daily. Antimycotics negatively affect the development of most species and should be used at minimum working concentrations. The protein source used in vitro may be important for host-specific mussels species, but host-generalists can be successfully cultured in either mammalian or fish serum sources, though fish serum may possess natural antibiotics that aid the control of microbial contamination. Juveniles in cultures containing fish serum increase their lipid reserves significantly over their levels as glochidia, but it is unknown how the lipid levels compare to juveniles cultured on host fishes. Lipid fortified media produces animals with high survivorship post-metamorphosis but data are conflicting as to whether the fortified media produces juveniles with greater lipid reserves than media without lipid supplements. With modifications to the in vitro medium and protocol, juvenile mussels can be easily and consistently cultured without host fishes. One cohort of Lampsilis siliquoidea was cultured in vitro using mammalian serum in the culture medium and the juveniles were grown in hatchery conditions for one year after metamorphosis. The growth of the juveniles as measured by total length exceeded the predicted length based on Von Bertalanffy growth equations, indicating our juveniles possessed no immediately observable developmental abnormalities. Variation of size, periostracum coloration and ray patterns were highly variable in the juveniles; diverse phenotypes are typical of wildtype populations and suggestive that our method may not be selective or reduce the genetic diversity of the animals to be used to bolster natural populations. Overall, we feel that with our modifications, we can successfully culture healthy, viable juveniles for bolstering existing populations of freshwater unionids. Our method also allows for the efficient production of juvenile mussels in a laboratory setting for toxicity testing, genetic work and general histological and physiological research.

    For full-text documents see ProQuest's Dissertations & Theses Database

  4. An integrative approach to understanding mussel community structure: Linking biodiversity, environmental context and physiology

    by Spooner, Daniel Edward. Ph.D. The University of Oklahoma, 2007.

    Abstract (Summary)
    The research detailed in my dissertation broadens our understanding of the biodiversity-ecosystem function paradigm using long-lived invertebrates in a freshwater ecosystem. Freshwater mussels (Unionoidea) are a globally threatened fauna with 70% of taxa considered threatened, yet little is known concerning their functional role. In addition to species extinctions, the overall biomass of both abundant and rare unionid species is declining in most rivers, and this loss of filter-feeding biomass is predicted to impact river function.

    My first chapter integrated biodiversity partitioning techniques with mussel community data across twenty one mussel beds to determine if mussel community biomass could be explained by patterns of species richness or species dominance. This partitioning approach tested the null hypothesis that biomass accrual within mussel beds is equal at all sites. The results of this work demonstrated that mussel biomass is largely explained by complementarity, which indicates that either niche partitioning or facilitation between mussel species is occurring. This conclusion was further supported by the fact that complementarity was highest in species rich, thermally variable mussel beds. In addition, numerically rarer species were in better condition (reduced oxygen consumption rates and higher body condition indices) in species-rich, thermally variable mussel beds which suggests that there is an energetic benefit to living in species rich communities.

    The research detailed in my second chapter built upon observed patterns of alternating species dominance by asking if different mussel species performed differently under a variety of thermal regimes. To address this question, I acclimated eight mussel species ( Lampsilis cardium, Fusconaia flava, Actinonaias ligamentina, Megalonaias nervosa, Amblema plicata, Quadrula pustulosa, Obliquaria reflexa , and Truncilla truncata ) to four temperatures (5, 15, 25, and 35°C). I quantified resource acquisition (clearance rate and oxygen consumption), assimilation (glycogen, body condition index, and Q10 rates of anabolism and catabolism), and ecosystem services (ammonia and phosphorus excretion rates, and biodeposition rates) using temperature-controlled respirometers. The results of this experiment demonstrate that although mussels are generally categorized as "filter feeders", there are distinct guilds within this functional group associated with their response to temperature. Megalonaias nervosa, Amblema plicata, Obliquaria reflexa , and Fusconaia flava are thermally-tolerant species assimilating energy at 35°C and increasing the magnitude of services (nutrient excretion, clearance and biodeposition rates) they contribute to ecosystems. Alternatively, A. ligamentina, L. cardium, Q. pustulosa , and Truncilla truncata appear to be thermally-sensitive with increased rates of catabolism at 35°C. However, the functional responses of thermally-sensitive species appeared to differ with some species decreasing filtration activity and increasing rates of nutrient excretion and others increasing both filtration and nutrient excretion rates. Extrapolating these data to real mussel communities highlighted the importance of the relative dominance between thermally-sensitive and tolerant-species under differing environmental contexts. Furthermore, shifts in community structure would be predicted to influence the nature of filtration, biodeposition and nutrient dynamics under current models of climate change.

    The focus of my third chapter is an integration of the physiology information collected in chapter two to address how species dominance of two distinct thermal guilds (thermally-tolerant and thermally-sensitive) influences gross primary production. I manipulated temperature (15, 25, and 35°C) and species dominance of five mussel species ( A. ligamentina, A. plicata and Q. pustulosa, M. nervosa , and O. reflexa ) using 1101 re-circulating stream mesocosms housed in an environmentally-controlled room. I quantified individual-based measures of resource acquisition (oxygen consumption, body condition index) and ecosystem services (ammonia and phosphorus excretion rates) for each species. In addition, I quantified gross primary production in the water column, benthos, and the entire stream mesocosm. Gross primary production was highest at 35°C and was positively related to both A. ligamentina and A. plicata dominance with communities. However, species dominance differentially influenced gross primary production of different compartments within the mesocosms with A. plicata (a thermally-tolerant species) positively influencing benthic production, and A. ligamentina (a thermally-sensitive species) positively influencing water column production. Species interactions within treatments were context dependent with A. ligamentina positively influencing A. plicata, M. nervosa , and O. reflexa at 25°C and negatively influencing M. nervosa and O. reflexa at 35°C. In addition to influencing resource acquisition, species dominance also influenced species-specific nutrient excretion rates and subsequently water-column nutrient levels.

    For full-text documents see ProQuest's Dissertations & Theses Database