The data of a previous experiment (Severini et al. 2010) are re-processed to evaluate the sensitivity of tadpole developmental rate to small variations of weak extremely low frequency magnetic flux densities (in two different aquariums E1 and E2).
Two cohorts of 35 tadpoles were exposed during their immature period (whole larval stage) at two different magnetic flux densities and two comparable cohorts served as controls. The experiment was replicated three times (with litters from three different frog pairs).
Exposure duration: continuous for 22 days
|Exposure duration||continuous for 22 days|
|magnetic flux density||70.1 µT||mean||calculated||-||+/- 0.3 µT in the center of E1|
|magnetic flux density||72.4 µT||mean||calculated||-||+/- 0.4 µT in the center of E2|
|magnetic flux density||63.9 µT||minimum||measured||-||E1|
|magnetic flux density||76.4 µT||maximum||measured||-||E1|
|magnetic flux density||68.4 µT||minimum||measured||-||E2|
|magnetic flux density||76.4 µT||maximum||measured||-||E2|
The data showed that tadpoles of aquarium E2 under the stronger field matured with a significant delay of 2.5 days with respect to tadpoles of aquarium E1 under the weaker field. This delay was clearly caused by exposures to two slightly different ranges of magnetic flux densities. The results suggest the existence of a field threshold around 70 µT in controlling the animal's developmental rate.