Multi-Level Effects of Low Dose Rate Ionizing Radiation on Southern Toad, Anaxyrus [Bufo] terrestris

• Published in: PloS one Vol. 10; no. 4; p. e0125327
• Main Authors: Stark, Karolina, Scott, David E, Tsyusko, Olga, Coughlin, Daniel P, Hinton, Thomas G
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 30-04-2015; Public Library of Science (PLoS)
• Subjects: Amphibia; Amphibians; Analysis; Animals; Background radiation; Bioassay; Bioassays; Blood cells; Body Size - radiation effects; Bufo terrestris; Bufonidae - growth & development; Cell division; Cesium isotopes; Cesium radioisotopes; Comet assay; Contaminants; Damage detection; Deoxyribonucleic acid; Developmental stages; DNA; DNA damage; DNA Damage - radiation effects; Ecotoxicology; Embryogenesis; Embryos; Erythrocytes; Exposure; Female; Hatching; Ionizing radiation; Laboratories; Larvae; Life Cycle Stages - radiation effects; Male; Metamorphosis; Organisms; Oviposition; Population; Radiation; Radiation Dosage; Radiation effects; Radiation, Ionizing; RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT; Radiosensitivity; Red blood cells; River ecology; Soil sciences; Survival; Terrestrial environments; Toads; Toxicity; Vertebrates
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0125327

Despite their potential vulnerability to contaminants from exposure at multiple life stages, amphibians are one of the least studied groups of vertebrates in ecotoxicology, and research on radiation effects in amphibians is scarce. We used multiple endpoints to assess the radiosensitivity of the southern toad (Anaxyrus [Bufo] terrestris) during its pre-terrestrial stages of development -embryonic, larval, and metamorphic. Toads were exposed, from several hours after oviposition through metamorphosis (up to 77 days later), to four low dose rates of 137Cs at 0.13, 2.4, 21, and 222 mGy d-1, resulting in total doses up to 15.8 Gy. Radiation treatments did not affect hatching success of embryos, larval survival, or the length of the larval period. The individual family variation in hatching success of embryos was larger than the radiation response. In contrast, newly metamorphosed individuals from the higher dose-rate treatments had higher mass and mass/length body indices, a measure which may relate to higher post-metamorphic survival. The increased mass and index at higher dose rates may indicate that the chronic, low dose rate radiation exposures triggered secondary responses. Additionally, the increases in growth were linked to a decrease in DNA damage (as measured by the Comet Assay) in red blood cells at a dose rate of 21 mGy d-1 and a total dose of 1.1 Gy. In conclusion, the complex effects of low dose rates of ionizing radiation may trigger growth and cellular repair mechanisms in amphibian larvae.