University of SaskatchewanHARVEST
  • Login
  • Submit Your Work
  • About
    • About HARVEST
    • Guidelines
    • Browse
      • All of HARVEST
      • Communities & Collections
      • By Issue Date
      • Authors
      • Titles
      • Subjects
      • This Collection
      • By Issue Date
      • Authors
      • Titles
      • Subjects
    • My Account
      • Login
      JavaScript is disabled for your browser. Some features of this site may not work without it.
      View Item 
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item

      Biotransformation of selenium and arsenic in insects : environmental implications

      Thumbnail
      View/Open
      RuwandiE.pdf (1.390Mb)
      Date
      2009-07-09
      Author
      Andrahennadi, Ruwandi
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
      Show full item record
      Abstract
      Living organisms constantly respond to changing environmental conditions, and some changes can be far from optimal for many organisms. Insects represent the majority of species in many ecosystems and play an important role in bioaccumulation and biotransformation of environmental contaminants such as selenium and arsenic. Some insectivorous predators feeding on these insects are highly sensitive to such elements resulting in reduced growth, reproductive failures and low population numbers. The mechanisms of selenium and arsenic uptake through the food chain are poorly understood. The determination of chemical speciation is a prerequisite for a mechanistic understanding of a contaminant’s bioavailability and toxicity to an organism. Synchrotron-based X-ray absorption spectroscopy was used to identify the chemical form of selenium and arsenic in insects in both the field and laboratory conditions. Insects living in streams near Hinton, Alberta affected by coal mine activities were examined for selenium speciation. Results showed higher percentages of inorganic selenium in primary consumers, detritivores and filter feeders than in predatory insects. Selenides and diselenides constitute a major fraction of selenium in these insects. In another field setting, speciation of selenium was studied in insects attacking selenium hyperaccumulating plant Astragalus bisulcatus. The effect of selenate and arsenate alone and the combined effects of selenate and arsenate on insects and parasitoids were monitored using a laboratory-reared moth (Mamestra configurata). Hosts receiving selenium biotransformed selenate to organic selenides and diselenides, which were transferred to the parasitoids in the third trophic level. Arsenic fed larvae biotransformed dietary arsenate to yield predominantly trivalent arsenic coordinated with three aliphatic sulfurs. Larvae receiving arsenate used a novel six-coordinated arsenic form as an excretory molecule in fecal matter and cast skin. X-ray absorption spectroscopy imaging with micro X-ray fluorescence imaging on selenate and arsenate fed larvae revealed highly localized selenium and arsenic species, zinc and copper within the gut. The results provide insights into how the insects cope with their toxic cargo, including how selenium and arsenic are biotransformed into other chemical forms and how they can be eliminated from the insects. The implication of selenium and arsenic species in the diet of predators and detritivores is discussed.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Geological Sciences
      Program
      Geological Sciences
      Supervisor
      Pickering, Ingrid J.
      Committee
      Liber, Karsten; Nichol, Helen; George, Graham N.; Gardea-Torresdey, Jorge; Ansdell, Kevin
      Copyright Date
      July 2009
      URI
      http://hdl.handle.net/10388/etd-06302009-125949
      Subject
      Selenium
      Arsenic
      Chemical form
      Biotransformation
      Insects
      X-ray absorption spectroscopy
      Collections
      • Graduate Theses and Dissertations
      University of Saskatchewan

      University Library

      © University of Saskatchewan
      Contact Us | Disclaimer | Privacy