The periods of gravidity and glochidial release, required fish hosts, and age and growth characteristics of Fusconaia cuneolus were studied in the upper Clinch River, Virginia during 1986 and 1987. This summer brooder is gravid from mid-May through late July, releasing most glochidia in midJune. Gills of gravid females assume the color of enclosed conglutinates, and hues change from pink to peach as embryos mature to glochidia. As judged by diel sampling of stream drift, glochidia of the fine-rayed pigtoe are most abundant in the water column in early morning. A total of 1,619 fish representing 39 species were electroshocked and examined from the Clinch River at Slant for glochidial attachment. Prevalence of infestation of amblemine glochidia was highest on species of the Cyprinidae (27 to 46%), and six species were identified as possible fish hosts for the glochidia of the fine-rayed pigtoe. Amblemine glochidia were absent on non-cyprinid fish species. Glochidia exhibited host specificity in laboratory experiments, metamorphosing on the following seven minnow and one sculpin species: fathead minnow (Pimephales promelas), river chub (Nocomis micropogon), stoneroller (Campostoma anomalum), telescope shiner (Notropis telescopus), Tennessee shiner (Notropis leuciodus), white shiner (Notropis a/beo/us), whitetail shiner (Notropis galacturus), and mottled sculpin (Cottus bairdi). Tested species of sunfishes, catfishes, and darters did not serve as hosts. Age and growth characteristics were obtained by thin-sectioning shells collected in muskrat middens at Slant and Pendleton Island, Virginia. As predicted by the von Bertalanffy equation, the fine-rayed pigtoe achieves a maximum length of roughly 90 mm and age of 35 yr in the Clinch River. Annual growth in length averaged 5 mm/yr through age 10, decreasing to a rate of roughly 2 mm/yr thereafter. Based upon an age-length key, most individuals (50%) were of intermediate ages (13 to 16 yr). Specimens less than 10 yr old were uncommon, comprising only 22.4% of the deme at Slant. No individuals less than 6 yr old were found at Slant or Pendleton Island. Based on cohort structure at these sites, the fine-rayed pigtoe population appears to be declining in the Clinch River. A monitoring program is suggested. / Master of Science

The Leon River, a small-medium river in central Texas, is highly impacted by multiple impoundments, enrichment from agricultural runoff, and decreased dissolved oxygen levels. This degraded river contains sixteen unionid species, two of which are both endemic to the region and candidates for the federal endangered species listing (Quadrula houstonensis and Truncilla macrodon). While there is a short historical record for this river basin and a recent modern survey completed in 2011, zooarchaeological data adds evidence for conservation efforts by increasing the time depth of data available and providing another conservation baseline. Zooarchaeological data for the Leon River is available from the two Late Holocene archaeological sites: 41HM61 and the Belton Lake Assemblages. Data generated from these assemblages describe the prehistoric freshwater mussel community of the Leon River in terms of taxonomic composition and structure. By comparing this zooarchaeological data to the data generated by the longitudinal modern survey of the Leon River, long term changes within the freshwater mussel community can be detected. A conceptual model is constructed to evaluate how robusticity, identifiability, and life history ecology affect unionid taxonomic abundances in zooarchaeological data. This conceptual model functions as an interpretive tool for zooarchaeologists to evaluate forms of equifinality in zooarchaeological assemblages. This thesis determines differences between the late Holocene and modern freshwater community of the Leon River, explores how different alternative mechanisms influence zooarchaeological data, and exemplifies of how zooarchaeological data can be used for conservation biology.

Unionoid mussels are globally threatened and their conservation requires species-specific knowledge on their ecology and parasite-host interaction. Unio crassus is one of Europe’s most threatened unionoid species and has a temporary obligate parasitic life stage (glochidia) on fish. A lack of suitable hosts is probably a major limitation for mussel recruitment, but host species composition, suitability and availability in time and space have yet to be fully explored. This thesis examines different aspects of the host fish species, including their composition, suitability and ecological importance, in relation to U. crassus, using both field and laboratory studies. The effects of mussel and host density on mussel reproductive potential were considered, as were aspects of evolutionary adaptations between mussels and fish and how climate change may affect their interaction. The results show that U. crassus is a host generalist, parasitizing a variety of fish species. Host suitability and density, which varied among fish species and rivers, affected the level of glochidia encapsulation, hence mussel reproductive potential, more so than the density of mussels taking part in reproduction. Ecologically important hosts included both highly suitable primary hosts, and less suitable hosts that were highly abundant. Whether or not U. crassus has specific adaptations to its hosts to enhance juvenile transformation remains unclear. No distinct pattern of local adaptation was found, nor was there an effect of host fish presence on the timing of glochidia release by adult mussels. Instead, temperature played a major role, with results suggesting that changes in spring water temperature regimes can cause temporal and spatial mismatches in the mussel-host interaction. This thesis indicates that investigations of local mussel-host interactions help in identifying mechanisms important for unionoid conservation management and prioritization. / Många sötvattenmusslor har en komplex livscykel där larverna (glochidier) under sin utveckling till frilevande musslor parasiterar på gälarna hos lämpliga värdfiskar. Flera av våra musslor, såsom den tjockskaliga målarmusslan (Unio crassus), är globalt hotade och för att kunna bevara och förvalta dessa arter på bästa sätt behöver vi lära oss mer om deras ekologi och samspelet mellan musslan och dess värdfiskar. Avsaknaden av värdfiskar innebär förmodligen en stor begränsning för rekryteringen av juvenila musslor, men det finns trots detta en begränsad kunskap om hur artsammansättningen i fisksamhället och dess tillgänglighet påverkar musselpopulationer.  Min avhandling undersöker olika aspekter av interaktioner mellan U. crassus och dess värdfiskar, som hur värdfisksamhällen och fiskarters värdlämplighet påverkar musslans reproduktionspotential. Jag har även studerat hur tätheter av olika fiskarter och vuxna musslor påverkar rekryteringen, eventuella evolutionära anpassningar samt om en förhöjd temperatur skulle kunna påverka interaktionen mellan U. crassus och dess värdfiskar. Resultaten visar att U. crassus är en generalist som parasiterar på en mängd olika fiskarter. Jag fann dock en stor variation i dominerande fiskarter och lämpliga värdar mellan olika åar, vilket påverkade reproduktionspotentialen hos musslorna mer än vad tätheten vuxna musslor som deltog i reproduktionen gjorde. Som ekologiskt viktiga värdar fanns således både särskilt lämpliga, primära värdarter, men också mindre lämpliga arter som förekom i höga tätheter. Ingen tydlig lokal anpassning kunde observeras, och fiskens närvaro påverkade inte tidpunkten för när de vuxna musslorna släppte sina glochidielarver. Däremot fann jag att temperaturen spelade en viktig roll för musslans reproduktion, där ökad temperatur föreslås ha negativa effekter på interaktionen mellan musslan och dess värdfiskar. Avhandlingen visar på vikten av att studera interaktioner mellan den tjockskaliga målarmusslan och dess värdar på lokal skala för att bättre kunna identifiera och prioritera viktiga naturvårdsåtgärder. / UnioCrassusforLIFE (European LIFE+ project: LIFE10 NAT/SE/000046)

The Upper Mississippi River (UMR) basin contributes over 50,000 metric tons of nitrogen (N) to the Gulf of Mexico each year, resulting in a “dead zone” inhospitable to aquatic life. Land-applied N (fertilizer) in the corn-belt is attributed with a majority of the N-load reaching the Gulf and is difficult to treat as run-off is considered a non-point source of pollution (i.e. not from a pipe). One solution to this “grand challenge” of intercepting N pollution is utilizing filter-feeding organisms native to the UMR. Freshwater mussel (order Unionidae) assemblages collectively filter over 14 billion gallons of water, remove tons of biomass from overlying water, and sequester tons of N each day. Our previous research showed mussel excretions increased the sediment porewater concentrations of ammonium by 160%, and indirectly increased nitrate and nitrite by 40%, presumably from microbial degradation of ammonium. In response, the goal of this research was to characterize how mussels influenced microbial communities (microbiome) to determine the fate of N in UMR sediment. First, we used qPCR and non-targeted amplicon sequencing within sediment layers to identify the N-cycling microbiome and characterized microbial community changes attributable to freshwater mussels. qPCR identified that anaerobic ammonium oxidizing (anammox) bacteria were increased by a factor of 2.2 at 3 cm below the water-sediment interface when mussels were present. Amplicon sequencing of sediment at depths relevant to mussel burrowing (3 and 5 cm) showed that mussel presence reduced microbial species richness and diversity and indicated that sediment below mussels harbored distinct microbial communities. Furthermore, mussels increased the abundance of ammonia oxidizing bacteria (family Nitrosomonadaceae), nitrite oxidizing bacteria (genus Nitrospira), but decreased the abundance of ammonia oxidizing archaea (genus Candidatus Nitrososphaera), and microorganisms which couple denitrification with methane oxidation. These findings suggested that mussels may enhance microbial niches at the interface of oxic and anoxic conditions, presumably through excretion of N and burrowing activity. In response, we performed metagenomic shotgun sequencing to identify which genes of the microbiome were most impacted by mussels. We hypothesized that genes responsible for ammonia and nitrite oxidation would be greater in the sediment with mussel assemblages. We found the largest abundance of N-cycling genes were responsible for nitrate reduction and nitrite oxidation, which is corroborated by the high concentration of nitrates in UMR water. Linear discriminant analysis statistical analyses showed nitrification genes were most impacted by mussels, and this presented an opposing effect on genes responsible for producing nitrous oxide, a potent greenhouse gas. Further investigation showed an increased abundance of a novel organism capable of completely oxidizing ammonia to nitrate (Candidatus Nitrospira inopinata) and coexisted with metabolically flexible Nitrospira (sp. moscoviensis), likely enhancing both carbon and N-cycling. We demonstrated that native mussels harbor a unique niche for N-cycling microorganisms with large metabolic potentials to degrade mussel excretion products. Our findings suggest the ecosystem services of mussels extend beyond water filtration, and includes enhanced biogeochemical cycling of carbon, N, and reduces the potential for a potent microbially-produced greenhouse gas. Ultimately, this research could be used to advocate for mussel habitat restoration in the UMR to lessen the impacts of non-point pollution.

Freshwater mussels are a viable option to detect real-time changes in water quality within aquatic ecosystems. Known as ecosystem engineers, freshwater mussels are constantly filtering particles and recycling nutrients in the benthic community. Therefore, identifying their physiological responses to alterations in water quality will enable mussels to not only serve as biomonitors but help model their impact on nitrogen cycle. This research focuses on identifying how mussel gape and heart rate respond to the addition of phytoplankton following a period of limited food availability. Immediately following phytoplankton addition, mussels show a decreased gape position linked with changes heart rate. As the gape returns to an open position, overlying ammonia concentrations increase showing an end of the metabolism process. As a result, pairing physiological changes with increased concentrations of phytoplankton, freshwater mussels' impact on ammonium concentrations can be accurately predicted. By inputting experimental excretion rates combined with variations in gape position, dynamic models will be simulate ammonium concentrations in the overlying water.

Labeled by the National Academy of Engineering (NAE) as one of fourteen Grand Challenges for Engineering, the management of the nitrogen cycle has become an increasingly difficult obstacle for sustainable development. In an effort to help overcome this challenge, the goal of our study is to expand on the limited scientific understanding of how the nitrogen cycle within aquatic environments may be affected by increasing human- and climate-induced changes. To this end, we are using freshwater mussels as a sentinel species to better understand the impacts of ecosystem perturbation on nitrogen processing in large river systems. This was completed by examining the physical, biological, and chemical characteristics of a mussel habitat in the Mississippi River, evaluating the impact of the 2008 floods on the habitat and the ecosystem's nutrient processing, establishing a well-equipped mussel laboratory habitat to investigate mussel behavioral responses, and analyzing highly time resolved data to examine the mussels' contribution to daily nitrate fluxes.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 2004. / Title from PDF t.p. (viewed on Dec. 7, 2005). Vita. In abstract the "E" in HE is subscript. Includes bibliographical references.

Freshwater mussels are the most imperiled group of freshwater invertebrates globally. Recent research suggests a better understanding of mussel feeding ecology may facilitate and improve conservation efforts. The use of stable isotopes is becoming an increasingly common method to study aquatic food webs. Carbon (C) and nitrogen (N) are two of the most frequently employed elements in food web studies. Differences in natural abundance of 13C/12C can indicate which food sources are the basal sources of carbon incorporated into a consumer’s tissue, while the ratio of 15N /14N provides a method of assessing trophic position within a food web. Attached macroalgae, including the genus Cladophora, may be the dominant primary producers in running water systems. Cladophora, however, has not yet been indicated as a prominent assimilated food source for freshwater mussels. The overall purpose of this study was to assess if the diet of two common Green River mussel species, Amblema plicata (Say) and Elliptio dilatata (Rafinesque) were influenced by the seasonal change in availability of Cladophora during a summer-autumn rapid growth period. Two specific questions were asked: 1) Are the assimilated diets different between control and treatment areas, and 2) are the assimilated diets influenced by differing Cladophora levels across the study period? A mesocosm approach was employed in order to manipulate Cladophora levels within a treatment area. Seventy-two mussels, 36 each species, were sampled across four months,twice between control (= reach-scale, heavy Cladophora cover) and treatment (= localscale removal of Cladophora) areas. The freeware program, IsoSource, a concentration weighted linear mixing model, was used to determine the potential contribution of potential food sources to the diet of both mussel species. IsoSource revealed that Cladophora was the primary assimilated food source for both species across the study period. Although assimilated diets were not different between control and treatment areas, diets were, however, influenced by Cladophora availability across time. The results of this study indicate that, during bloom conditions, Cladophora is the primary carbon source for both A. plicata and E. dilatata and may form the base of food webs in the upper Green River.

Thesis (Ph. D.)--University of Michigan, 1934. / Thesis note on label mounted on t.p.; also on p. [7]. Descriptive letterpress on versos facing the plates. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 78-83.

Thesis (Ph. D.)--University of Michigan, 1934. / Thesis note on label mounted on t.p.; also on p. [7]. Descriptive letterpress on versos facing the plates. Bibliography: p. 78-83.