Author : Christopher T. Owen
Publisher :
ISBN 13 :
Total Pages : 298 pages
Book Rating : 4.:/5 (654 download)
Book Synopsis Investigations for the Conservation and Propagation of Freshwater Mussels by : Christopher T. Owen
Download or read book Investigations for the Conservation and Propagation of Freshwater Mussels written by Christopher T. Owen and published by . This book was released on 2009 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
