Effects of low-dose ionizing
radiation on
larval Rana catesbeiana (bullfrog)
Karolina Stark--Research Projects--SREL
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Effects of low-dose ionizing
radiation on |
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Experiment design
Hypothesis: Current regulatory guidance on acceptable dose rates to aquatic organisms (10mGy/d) established by IAEA (1992), sufficiently protects frogs under chronic and acute exposure conditions.
Facility: LoDIF with 137Cs-sources at Par Pond Laboratory. The LoDIF consists of 40 tanks divided into 8 blocks with 5 tanks in each block. 4 tanks in every block will be used for the different treatments. A total of 4 blocks will be used during the exposure period in the experiment. In addition, a high irradiation source in the H-area at the Savannah River Site (SRS) will be used for the acute exposures of frogs.
Frog species: Rana catesbeiana (Bullfrog), inhabitant of SRS. Typical frog and life-cycle. Large tadpoles. For Bullfrog up to 15 cm and a larval period of 2 years.
Prior to this experiment, tadpoles (in pre-metamorphosis stage) will be collected in the field on the SRS and brought to lab. The stage and size of the tadpoles will be recorded.
In this experiment we hypotheses that 10 mGy/d sufficiently protect frogs under chronic and acute exposure conditions. We test our hypothesis by exposing frog tadpoles to dose rates of 0, 1.8, 18, and 180 mGy/d for 21 days. An exposure period of 21 days would result in a total dose of 0, 0.038, 0.38, and 3.8 Gy, respectively. Three buckets (size: 16 L) will be placed in the center of every tank. In total 48 buckets will be used. Every bucket has 3 holes in them covered with nets that allow a flow-through system of water in the tanks.
In one bucket in every tank 4 tadpoles will be placed. The remaining buckets in the tank will be empty and serve as support for that other bucket. The exposure will be interrupted three times to record mortality and feeding. The tadpoles will also have excess to algae and periphyton in the buckets as food during the whole exposure period. The exposure period will be ended after 21 days. A total of 64 tadpoles will be exposed in the LoDIF.
In addition, (4 x 4) tadpoles will be exposed to an acute dose of 0, 1.5, and 3.0 Gy. These tadpoles can be used as positive samples to verify that the molecular endpoint is working or/and they (the 3.0 Gy group) can also be used as a comparison of acute vs. chronic dose. One group in the LoDIF will receive a total dose of 3.8 Gy during 21 days and the other group of tadpoles will receive an acute dose of 3.0 Gy. The acute-exposed tadpoles and the chronic-exposed tadpoles can all be used for construction of a dose rate – response curve for frogs and the molecular endpoint.
When the exposure period is ended, blood samples will be collected from the tadpoles by cardiac puncture. The size and stage of the tadpoles will be recorded.
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