Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

The reproductive biology of four unionid mussels, Actinonaias carinata, Elliptio dilatata, Cyclonaias tuberculata, and Tritogonia verrucosa, from the New River in Virginia and West Virginia was investigated. The gametogenic cycle, length and timing of spawning and glochidial release periods, and age at sexual maturity were described for each species. Comparisons of growth rates of C. tuberculata subpopulations from the Greenbrier River and three locations downstream of Bluestone Dam on the New River in West Virginia were also made to determine the effect of the dam on growth of mussels downstream. A. carinata is bradytictic, spawning in mid-summer, brooding glochidia throughout the fall and winter, and releasing them in the spring. E. dilatata, C. tuberculata, and T. verrucosa are tachytictic. Spawning began in mid-March for these three species and continued into May for T. verrucosa, into June for C. tuberculata, and into July for E. dilatata. Glochidia were released upon maturation, beginning in mid-April and continuing through June for T. verrucosa, and into August for E. dilatata. C. tuberculata released glochidia from March through June. All four species appeared to reach sexual maturity between the ages of 4 and 6, depending upon the species. Growth in shell length in the four subpopulations of C. tuberculata was asymptotic. Growth rate, described by the parameter w from a reparameterization of the von Bertalanffy growth equation, was significantly higher immediately below Bluestone Dam compared to the site furthest downstream. Growth of this species did not differ significantly among the other sites; however, a trend of decreasing growth rate with increasing distance from the dam was apparent. Observed differences in growth were attributed to differences in food availability and quality resulting from the operation of Bluestone Dam. / Master of Science

I examined the suspension feeding of four freshwater unionid mussels, Elliptio complanata, Elliptio dilatata, Fusconaia flava and Strophitus undulatus to help explain how more than 30 species can coexist in a single river, as well as to contribute new insights into their basic biology. I examined whether the flux of algae affected the suspension feeding (clearance rate, CR) of unionids in a flow chamber. CR varied with seston flux (J = UC, where U is the velocity and C is the algal concentration) for the 4 species examined. The lotic species (E. dilatata) cleared up to four times more water than lentic species (E. complanata). Differences in CRs were found among E. dilatata, F. flava, and S. undulatus from the same hydrodynamic habitat at the highest flux tested; the CR of E. dilatata varied with the hydrodynamics of its native river. These results provide new insight into how seston flux influences unionid suspension feeding, which may help to explain niche breadth in this group.

A thesis submitted to the School of Graduate Studies in partial fulfilment of the requirements for the degree of Master of Science in the graduate academic unit of Biology / Microparticles enter aquatic environments through many sources, including wastewater treatment plants (WWTPs), but their uptake by aquatic organisms is poorly understood. Freshwater bivalves accumulate multiple contaminants, making them potential bioindicators for MP pollution. This study aims to understand the abundance and characteristics of microparticles that accumulate in wild bivalves. Samples were collected from 5 locations along the Grand River (Ontario, Canada) in 2021-2022, including 3 municipal WWTPs where both an upstream and downstream site were sampled. At each site, fingernail clams (Sphaeriidae, n=5 composite samples), flutedshell mussels (Lasmigona costata, n=10), and surface water (n=3) were sampled. Within the mussels, the gill, digestive gland, and hemolymph tissues were targeted and compared. Microparticles were isolated and quantified via stereomicroscopy but have not yet been confirmed as plastic; as such, they will be referred to herein as microparticles. Fibers were the dominant morphology and clear, blue, and black were the most common colours, but there were some differences among sites and sample types. Most microparticles were between 80 μm and 1 mm in length. Fingernail clams contained the highest microparticle counts per mass of tissue at 35.5 ± 29.4 microparticles/g, mussel tissues ranged from 4.3 ± 4.2 microparticles/mL to 6.5 ± 8.1 microparticles/g, and water samples contained the lowest counts at 0.0055 ± 0.0028 microparticles/mL. Elevated microparticle counts at downstream sites were only seen in mussel gills and not other bivalve tissues. Surface water samples did not show elevated counts downstream of the WWTPs and microparticle exposures were similar across sites. This study provides baseline data for future monitoring and informs toxicity studies to fully assess the risk of microparticles to vulnerable freshwater bivalves and other aquatic organisms. It also suggests microparticles in freshwater bivalves are coming from sources in addition to WWTPs and are ubiquitous in the Grand River. / Thesis / Master of Science (MSc) / Microplastics are found in nearly every environment, especially freshwater ecosystems. These plastics come from a variety of sources, and this study focuses on assessing the characteristics of microparticles in freshwater clams and mussels (bivalves) that have been exposed to municipal wastewaters. Bivalves and water samples were collected from 5 locations along the Grand River (Ontario, Canada) in 2021-2022, and microparticles were extracted and analyzed from each sample. Fibers were the most abundant type of microparticle, with colours consisting mostly of clear, blue, and black. Clams had the highest number of microparticles per mass of tissue collected and the lowest counts were found in water samples. Higher microparticle counts were only seen in one (mussel gill) of the four tissues from bivalves collected downstream of wastewater outfalls. This study provides baseline data on microparticle characteristics in freshwater bivalves and will guide future studies on the toxicity of microparticles to these animals.

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. / Ph. D.

There is a great deal of concern about the declining freshwater mussel fauna of North America. Although deteriorating water quality and habitat degradation may account for much of the decline, it has been suggested that the exotic Asian clam, Corbicula fluminea, may be having an effect on native unionids. Negative impacts may result directly from competition or indirectly, because of Corbicula population crashes that release ammonia and reduce dissolved oxygen in the sediment. Laboratory tests were conducted to determine the relative sensitivity of native mussel and Asian clam life stages to unionized ammonia, and mussel glochidia were the most sensitive (24-hr LC50 of 0.11 mg/L NH₃-N). Juvenile and adult mussels were similarly sensitivity, with average 96-hr LC50's of 0.49 and 0.52 mg/L NH₃-N, respectively. Adult C. fluminea were the least sensitive, having an average LC50 of 0.80 mg/L NH₃-N. The EPA standard test organism, Ceriodaphnia dubia, had one of the lowest LC50's (0.07 mg/L NH₃-N) of the five species, and the fathead minnow, Pimephales promelas, had the highest (1.18 mg/L). The differing sensitivities of the various life stages are important when trying to determine the impact of an Asian clam dieoff. If a dieoff occurs at a time of year when the more sensitive life stages, such as glochidia are present, then the impact on mussel recruitment may be greater. Two miniature artificial stream tests were used to determine the effect of clam density on dieoff rate, ammonia production and dissolved oxygen levels. Only clams at the highest density of 10,000/m2 experienced 100% mortality. Unionized ammonia levels exceeded 4.0 mg/L, and dissolved oxygen levels dropped below 1.0 mg/L during the dieoff. The amount of unionized ammonia produced was twofold greater than the concentration that produced an LC50 in adult C. fluminea and ~40 times greater than the LC50 for V. iris glochidia. Factors thought to have contributed to the C. fluminea dieoff were flow rate, low dissolved oxygen levels, temperature and perhaps ammonia. A complete dieoff did not occur until flow was stopped and dissolved oxygen concentrations began to drop. One-hundred percent mortality occurred in 38 days for the first test, and 21 days in the second test. Higher water temperatures in the first test (26° C) compared to the second test (average = 21.7°C) are thought to have resulted in the faster dieoff. / Master of Science

The anthropogenic alteration of riverine ecosystems has led to declines in the abundance and diversity of freshwater mussels (Bivalvia: Unionoida) worldwide. Central Texas is home to a diverse freshwater mussel fauna including three candidates for federal listing under the Endangered Species Act. Surveys conducted over the last few decades suggest many of the endemic freshwater mussel species in Texas exist in small isolated populations that may be vulnerable to the deleterious effects of genetic diversity loss. Microsatellite primers from two closely related species were used to identify a set of genetic markers that functioned in the Golden Orb (Quadrula aurea). Microsatellite markers were then applied to document the population genetic structure of Q. aurea within and among three connected river drainages in southeastern Texas. Gene flow within existing Q. aurea populations appears high indicating little potential for genetic issues stemming from isolation and inbreeding. Two weakly divergent admixed populations were identified occupying the San Antonio and Guadalupe/San Marcos rivers. Population genetic structure was related to river basin affiliation, but results for environmental factors were unresolved. Current effective population size estimates are large for the Guadalupe/San Marcos drainage and moderately large for the San Antonio drainage and there is no clear genetic evidence of contemporary population declines. Transport in the glochidial phase by a highly mobile host fish, the channel catfish (Ictalurus punctatus), may provide a mechanism for maintaining connectivity among spatially discrete mussel beds and deserves further study. Information on the occurrence and habitat associations of Q. aurea and two other threatened freshwater mussel species was documented. Quantification of the population genetic structure for Q. aurea provides important information needed for the management of this species, a baseline for understanding future changes, and insight into the factors that shape the population genetic structure of other threatened unionids in Texas.

Growth rates, age-frequency distributions, and mortality rates of six mussel species were examined at four sites in the Clinch River, Virginia and Tennessee, to identify potentially impacted sites in the upper river. The bioaccumulation of copper in mussel shells also was examined as a possible contributing factor to the declining mussel fauna. Higher growth rates observed at Hackneys site, river kilometer (RK) 433.7, may have been due to the discharge of domestic sewage from the town of Cleveland into the Clinch River. However, a sewage treatment facility was constructed in 1986 which removed the source of enrichment. Growth rates of female Lampsilis fasciola were significantly less than growth rates of male L. fasciola after 3 years of age, probably due to the onset of sexual maturity. Age-class distributions revealed an absence of recruited juveniles at the Slant site (RK 359.3) after 1977 to 1979 for four mussel species examined. Substantial erosion of stream banks in tributaries of the Clinch River and deposition of sediment in the Clinch River were observed at Slant, indicating a potential cause of decline. Mean annual mortality rates of adult mussels were extraordinarily high for all species at all sites, which confirms the overall decline of freshwater mussels in the upper Clinch River. There were no statistically significant differences in accumulation of copper in shells of L. fasciola among sites or sexes. Although Appalachian Power Company’s Clinch River Plant (CRP) had a history of high copper levels in the effluent discharge, it is apparently not the cause of reduced recruitment at the Slant site, located 72 km downstream. As indicated by this research, water quality or habitat conditions of the upper Clinch River continue to be insufficient to sustain freshwater mussels. The CRP has improved the effluent discharge to contain less than 12 μg Cu/L, which should improve conditions directly downstream; however, erosion of stream banks, sewage treatment facilities, and agricultural and urban runoff, continue to contribute to the demise of a rich freshwater mussel fauna. / Master of Science

I investigated whether Neogobius melanostomus, an invader of biodiversity “hot-spots” in Ontario facilitates or inhibits unionid mussel recruitment by serving as a host or as a sink for their parasitic larvae (glochidia). Infestation and metamorphosis rates of four mussel Species at Risk (Epioblasma torulosa rangiana, Epioblasma triquetra, Lampsilis fasciola, and Villosa iris) and one common species (Actinonaias ligamentina) on N. melanostomus were compared to rates on known hosts in the laboratory. All species successfully infested N. melanostomus, but only E. triquetra, V. iris, and A. ligamentina successfully metamorphosed, albeit at low rates. Neogobius melanostomus collected from areas of unionid occurrence in the Grand and Sydenham rivers exhibited body burdens of 39.4% and 5.1%, respectively. Analyses indicate that N. melanostomus serves more as a sink for glochidia than as a host for unionids, thereby limiting recruitment, which is a novel way by which N. melanostomus is affecting native mussel species.

Mussel studies in the Tennessee River drainage (1973 - 1982) examined ecology and distribution and investigated factors limiting to distribution. This river system presently supports 71 freshwater mussel species, 25% of which are endemic to the Cumberlandian Region. Species have been extirpated from this drainage within the past 60 years, however the number of extant species remains high. The major impact of man's activities has been reduction of available habitat. Past and present distribution records indicate that mussel species assemblages are determined by geologic history and stream size. Although some overlap of species exists among stream size categories, there is no longer a continuous gradation from one category to the next; mussels exist in isolated communities separated by nonproductive river reaches. Productive reaches supporting more than 60 mussel species once existed in habitats spanning the transition from medium to large rivers; reaches now altered by impoundment. The maximum number of species reported in recent collections from any one site in the Tennessee drainage is less than 40, which seems to be the maximum number of species niches available. Quantitative sampling reveals characteristic patterns of species dominance. Changes in species dominance and age class structure provide a better basis for evaluating changes over time than do species composition or diversity alone. Mussel density was found to be more variable than species composition, and was unrelated to species abundance. Experiments on effects of siltation indicated that silt can be a significant limiting factor to mussel distribution. Transplant studies showed that mussels transplanted into heavily silted areas exhibited poor survival over a one year period compared to mussels moved to unsilted habitats. Results indicate that siltation may interfere with reproductive activity. Laboratory experiments testing the effect of suspended silt on the uptake of C-14 tagged algae by freshwater mussels showed that suspended silt can interfere with feeding. Food uptake was reduced to approximately 50% (of control) at silt levels of 211 to 820 mg/l, and to 80% at silt levels over 1000 mg/l. It was concluded that the limiting mechanism is one of dilution of food rather than direct interference with filtration or respiration. / Ph. D.