Lizards respond to an extremely low-frequency electromagnetic field

Tsutomu Nishimura,Masanori Fukushima,Hideyuki Okano,Etsuko Nishimura,Harue Tada,Kenji Sugimoto,Kaneo Mohri

doi:10.1242/jeb.031609

Abstract

Animals from a wide range of taxa have been shown to possess magnetic sense and use magnetic compasses to orient; however, there is no information in the literature on whether lizards have either of these abilities. In this study, we investigated the behavioral responses of a diurnal agamid lizard (Pogona vitticeps) to a sinusoidal extremely low-frequency electromagnetic field (ELF-EMF; 6 and 8 Hz, peak magnetic field 2.6 microT, peak electric field 10 V m(-1)). Fourteen adult lizards were divided randomly into two groups (the EMF and control groups; each group had three males and four females). The EMF group received whole-body exposure to ELF-EMF and the control group did not. Lizards in the EMF group were exposed to ELF-EMF for 12 h per day (during the light period). The number of tail lifts was monitored beginning 3 days before exposure and ending after 5 days of exposure. For each individual, the average number of tail lifts per day was calculated. The average number of tail lifts per individual per day was greater in the EMF group than in the control group (20.7+/-6.3 and 9.1+/-4.5 tail lifts, respectively, N=7 each, P=0.02). We confirmed the reproducibility of this response by a cross-over trial. These results suggest that at least some lizards are able to perceive ELF-EMFs. Furthermore, when the parietal eye of the lizards was covered with a small round aluminum 'cap' which could block light, the tail-lifting response to ELF-EMF disappeared. Our experiments suggest that (1) lizards perceive EMFs and (2) the parietal eye may be involved in light-dependent magnetoreceptive responses.

Highlights

In their review of magnetoreception in animals, Wiltschko and Wiltschko (Wiltschko and Wiltschko, 2006) present evidence showing that animals from a wide range of taxa possess magnetic sense and use magnetic compasses to orient
The thresholds of sensitivity to changes in the geomagnetic field are reported to be in the range of 10–200 nT (Walker et al, 2002) and magnetoreception mechanisms involving magnetite are sensitive to extremely low-frequency electromagnetic field (ELF-electromagnetic field (EMF)) up to Ϸ10 Hz (Kirschvink, 2000)
In which we evaluated the effects of an extremely low-frequency (ELF)-EMF on P. vitticeps, a continuous ELF-EMF for a few days evoked tail-lifting in the lizards more frequently during daytime hours (T.N., unpublished data)

Summary

INTRODUCTION

In their review of magnetoreception in animals, Wiltschko and Wiltschko (Wiltschko and Wiltschko, 2006) present evidence showing that animals from a wide range of taxa possess magnetic sense and use magnetic compasses to orient. The thresholds of sensitivity to changes in the geomagnetic field are reported to be in the range of 10–200 nT (Walker et al, 2002) and magnetoreception mechanisms involving magnetite are sensitive to ELF-EMFs up to Ϸ10 Hz (Kirschvink, 2000). We exposed P. vitticeps to ELF-EMFs and observed them to determine whether this non-migratory lizard species is behaviorally sensitive to ELF-EMFs. Because experimental evidence is accumulating that the threshold sensitivity of some animals to magnetic fields is less than a few tens of nanotesla (Walker et al, 2002), as a first step we exposed lizards to ELF-EMFs in the order of microtesla. We attempted to examine the behavioral responses of P. vitticeps to an EMF and to study whether or not the parietal eye of P. vitticeps is involved in a magnetoreceptive reaction by monitoring these behavioral responses

MATERIALS AND METHODS

RESULTS

DISCUSSION