Selenium speciation influences bioaccumulation in Limnodynastes peronii tadpoles.
Despite being essential for animal health and fitness, Se has a relatively narrow range between deficiency and toxicity, and excess Se can cause a variety of adverse effects in aquatic organisms. Amphibians are particularly vulnerable to contaminants during larval aquatic life stage, because they can accumulate toxic ions through various routes including skin, gills, lungs and digestive tract. Few attempts have been made to understand the tissue-specific accumulation of trace elements, including the impacts of chemical speciation in developing amphibian larvae. We used radiolabelled75Se to explore the biokinetics and tissue distributions of the two dominant forms occurring in surface waters, selenite (SeIV) and selenate (SeVI). Tadpoles of the native Australian frog Limnodynastes peronii were exposed to Se in both forms, and live-animal gamma spectroscopy was used to track accumulation and retention over time. Tissue biodistributions were also quantified at the end of the uptake and depuration phases. Results showed the bioconcentration of SeIV to be 3 times greater compared to SeVI, but rates of elimination were similar for both forms. This suggests a change of Se speciation within the organism prior to excretion. Depuration kinetics were best described by a one-phase exponential decay model, and tadpoles retained approximately 19% of the accumulated Se after 12 days of depuration in clean water. Selenium bioaccumulation was greatest in digestive and excretory organs, as well as the eye, which may directly relate to previously reported Se-induced impairments. Results demonstrate how the use of radiotracing techniques can significantly improve our understanding of trace element toxicokinetics and tissue distributions in developing amphibians. From an environmental monitoring perspective, the findings highlight the importance of considering chemical speciation as this could influence the accuracy of risk assessment.
Central Queensland University, School of Medical and Applied Sciences, Gladstone, QLD 4680, Australia; Australian Rivers Institute, School of Environment, Griffith University, Southport, QLD 4215, Australia. Electronic address: c.lanctot@griffith.edu.au.
C M
CM
Lanctôt
Australian Rivers Institute, School of Environment, Griffith University, Southport, QLD 4215, Australia. Electronic address: s.melvin@griffith.edu.au.
S D
SD
Melvin
Australian Nuclear Science and Technology Organisation (ANSTO), Locked Bag 2001, Kirrawee DC, NSW 2232, Australia. Electronic address: tom.cresswell@ansto.gov.au.
T
T
Cresswell
D000818:Animals; D001001:Anura; D001315:Australia; D004784:Environmental Monitoring / Q000379:methods*; D005880:Gills / Q000737:chemistry; D007814:Larva / Q000187:drug effects / Q000378:metabolism*; D008657:Metabolic Clearance Rate; D009928:Organ Specificity; D064586:Selenic Acid / Q000493:pharmacokinetics* / Q000633:toxicity; D020887:Selenious Acid / Q000493:pharmacokinetics* / Q000633:toxicity; D014018:Tissue Distribution; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics* / Q000633:toxicity
D014874:Water Pollutants, Chemical; D020887:Selenious Acid; D064586:Selenic Acid
Amphibian; Bioaccumulation; Radioisotope tracer; Selenate; Selenite; Selenium