title: Effects of dietborne copper and silver on reproduction by Ceriodaphnia dubia.
abstract: Recent studies have indicated the potential for dietborne metals as an important exposure pathway for metal toxicity in freshwater organisms. We conducted a study in which freshwater cladocerans (Ceriodaphnia dubia) were fed green algae (either Pseudokirchneriella subcapitata or Chlorella vulgaris) that were grown in Ag- or Cu-contaminated media. In one series of toxicity tests patterned after the U.S. Environmental Protection Agency's three-brood C. dubia chronic toxicity test, we exposed C. dubia to waterborne Ag or Cu while feeding them normal amounts of uncontaminated yeast-Cerophyll-trout chow (YCT) slurry and either algae grown in standard media or algae grown in standard media supplemented with Ag or Cu (added as AgNO3 or CuSO4 x 5H2O). These parallel tests demonstrated that dietborne metal did not contribute to survival or reproduction effects beyond the effects caused by waterborne metal alone. We also conducted dietborne-only toxicity tests patterned after two other recently published experimental designs in which (1) C. dubia were fed only metal-contaminated algae for 4 h, transferred to fresh water, and fed uncontaminated algae and YCT slurry for the duration of the three-brood test or (2) C. dubia were fed standard amounts of metal-contaminated algae and uncontaminated YCT slurry for the entire three-brood test. In contrast to previous studies, we did not find consistent dietborne metal toxicity or standard concentration-response relationships in those two experiments. Instead, among-experiment variation in intracellular partitioning of metals in the algae fed to the C. dubia, among-laboratory differences in experimental procedures, selective feeding by C. dubia to avoid metal-contaminated algae, an interaction between reproductive status of the C. dubia and dietborne metal concentration, or a combination of these might help explain the apparently inconsistent results.
authors: Department 3166, Zoology and Physiology, 1000 East University Avenue, University of Wyoming, Laramie, Wyoming 82071, USA.
authors: Jason M
authors: JM
authors: Kolts
authors: Connie J
authors: CJ
authors: Boese
authors: Joseph S
authors: JS
authors: Meyer
mesh_terms: D000818:Animals; D003300:Copper / Q000008:administration & dosage / Q000633:toxicity*; D003445:Crustacea / Q000187:drug effects* / Q000502:physiology; D004032:Diet; D056890:Eukaryota / Q000187:drug effects / Q000254:growth & development; D012098:Reproduction / Q000187:drug effects*; D012834:Silver / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D012834:Silver; D003300:Copper