title: Differential responses of juvenile and adult South African abalone (Haliotis midae Linnaeus) to low and high oxygen levels.
abstract: Marine invertebrates have evolved multiple responses to naturally variable environmental oxygen, all aimed at either maintaining cellular oxygen homeostasis or limiting cellular damage during or after hypoxic or hyperoxic events. We assessed organismal (rates of oxygen consumption and ammonia excretion) and cellular (heat shock protein expression, anti-oxidant enzymes) responses of juvenile and adult abalone exposed to low (~83% of saturation), intermediate (~95% of saturation) and high (~115% of saturation) oxygen levels for one month. Using the Comet assay, we measured DNA damage to determine whether the observed trends in the protective responses were sufficient to prevent oxidative damage to cells. Juveniles were unaffected by moderately hypoxic and hyperoxic conditions. Elevated basal rates of superoxide dismutase, glutathione peroxidase and catalase were sufficient to prevent DNA fragmentation and protein damage. Adults, with their lower basal rate of anti-oxidant enzymes, had increased DNA damage under hypoxic and hyperoxic conditions, indicating that the antioxidant enzymes were unable to prevent oxidative damage under hypoxic and hyperoxic conditions. The apparent insensitivity of juvenile abalone to decreased and increased oxygen might be related to their life history and development in algal and diatom biofilms where they are exposed to extreme diurnal fluctuations in dissolved oxygen levels.
authors.affiliation: School of Life Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban, 4000, South Africa. vosloo@ukzn.ac.za
authors.forename: Andre
authors.initials: A
authors.lastname: Vosloo
authors.forename: Anél
authors.initials: A
authors.lastname: Laas
authors.forename: Dalene
authors.initials: D
authors.lastname: Vosloo
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D020552:Comet Assay; D004249:DNA Damage; D053938:DNA Fragmentation; D004789:Enzyme Activation; D049851:Gastropoda / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D005979:Glutathione Peroxidase / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006433:Hemocyanins / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism; D009132:Muscles / Q000378:metabolism / Q000502:physiology; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors
chemical_list: D000975:Antioxidants; D018840:HSP70 Heat-Shock Proteins; D006433:Hemocyanins; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D010100:Oxygen