The effects of a chronic whole-body exposure of tadpoles to a 50 Hz magnetic field with 1 mT on the metamorphosis of the clawed frog should be investigated.
Three-day-old tadpoles were randomly assigned to four groups with 200 individuals each. Two groups were then transferred into aquaria exposed to the magnetic field for 65 days and two groups were transferred into aquaria with sham exposure. Data was collected from all aquaria each day until the end of exposure. Experiments were replicated four times.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 65 days
|
|
for further information on the setup see also: Grimaldi, S., Pozzi, D., Lisi, A., Rieti, S., Manni, V., Ravagnan, G., Giuliani, L., Eremenko, T., and Volpe, P. (2000) Influence of the magnetic field on tadpole metamorphosis. Int. J. Radiat. Med. 1(5), 96-103
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 65 days |
| Exposure source | |
|---|---|
| Setup | 960 mm long solenoid consisting of 620 turns of 1.5 mm diameter copper wire wound on a 1000 mm long G10 fiberglas cylindric tube with a diameter of 360 mm and a wall thickness of 8 mm; aquariums containing the tadpoles were located in 220 mm x 235 mm x 230 mm metacrylate amagnetic incubators whose temperature was kept constant by thermostated water baths; incubators for exposure placed inside the solenoid; field homogeneity greater than 98 % in the exposure area |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1 mT | - | measured | - | - |
At the end of the experiment (after 65 days), the total percentage of surviving individuals in exposed groups was not significantly different from sham exposed groups. However, especially during the first 10 days of exposure, the mortality in exposed groups was strikingly higher. This led to a significantly decreased survival-rate in exposed groups up to day 60. Metamorphosis was strikingly delayed with the maximum of daily metamorphosis occurring six days later in exposed than in sham exposed groups. Finally, metamorphosis was successful for 85% of individuals in sham exposed and for 45% of individuals in the exposed groups, respectively.
The authors conclude, that an exposure of claw frog tadpoles to a 50 Hz magnetic field has a distinct effect on their development.
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