Cryptochrome 2 mediates directional magnetoreception in cockroaches

Abstract

The ability to perceive geomagnetic fields (GMFs) represents a fascinating biological phenomenon. Studies on transgenic flies have provided evidence that photosensitive Cryptochromes (Cry) are involved in the response to magnetic fields (MFs). However, none of the studies tackled the problem of whether the Cry-dependent magnetosensitivity is coupled to the sole MF presence or to the direction of MF vector. In this study, we used gene silencing and a directional MF to show that mammalian-like Cry2 is necessary for a genuine directional response to periodic rotations of the GMF vector in two insect species. Longer wavelengths of light required higher photon fluxes for a detectable behavioral response, and a sharp detection border was present in the cyan/green spectral region. Both observations are consistent with involvement of the FADox, FAD•− and FADH -redox forms of flavin. The response was lost upon covering the eyes, demonstrating that the signal is perceived in the eye region. Immunohistochemical staining detected Cry2 in the hemispherical layer of laminal glia cells underneath the retina. Together, these findings identified the eye-localized Cry2 as an indispensable component and a likely photoreceptor of the directional GMF response. Our study is thus a clear step forward in deciphering the in vivo effects of GMF and supports the interaction of underlying mechanism with the visual system. magnetoreception | cryptochrome | light spectrum | locomotor activity | circadian genes

Increased motor activity of the beetle Laemostenus punctatus caused by a static magnetic field of 110 mT

“…It has been shown that cryptochromes in the photoreceptor neurons of bird eyes have an impact on magnetic orientation during migration (Heyers et al, 2007). Bazalova et al (2016) demonstrated a Cry-dependent sensitivity to the direction of geomagnetic field in two cockroach species -American cockroach, Periplaneta americana (L.), and German cockroach, Blattella germanica (L.)and the importance of the eye for the directional geomagnetic field response. It may help to determine the position of the geomagnetic north and aid orientation in space.…”

Exposure to extremely low frequency electromagnetic fields alters the behaviour, physiology and stress protein levels of desert locusts

“…These insects are able to detect very low levels of static magnetic fields and use them to drive orientated movements. There is also evidence for different mechanisms of magnetoreception by organisms responsive to these low level static magnetic fields in the environment, including direct detection through either ferromagnetic crystal (Fe 3 O 4 ) deposits910 or through cryptochrome molecules611.…”

A geomagnetic declination compass for horizontal orientation in fruit flies

“…Therefore, it is reasonable to consider that there has been no convincing evidence for the magnetic compass that underlies the observed flies' horizontal orientations. Second, recent studies that showed magnetosensitive body alignment in two animal species (Bazalova et al ; Hart et al ) supported the possibility that animals can exhibit magnetoreceptive behavior by sensing changes in declination without detection of the direction of geographic north. Cockroaches could sense repeated changes in magnetic direction caused by the shift of the horizontal component of the GMF; they showed significant correlated body alignment within an interval of a few minutes without any geographic directional cue in the testing arena (Bazalova et al ).…”

“…Second, recent studies that showed magnetosensitive body alignment in two animal species (Bazalova et al ; Hart et al ) supported the possibility that animals can exhibit magnetoreceptive behavior by sensing changes in declination without detection of the direction of geographic north. Cockroaches could sense repeated changes in magnetic direction caused by the shift of the horizontal component of the GMF; they showed significant correlated body alignment within an interval of a few minutes without any geographic directional cue in the testing arena (Bazalova et al ). In addition, the north–south body alignment of domesticated dogs during excretion in open fields was specifically dependent on the rate of change in the declination, but not the absolute value of declination or total‐, vertical‐, horizontal‐intensity of the GMF (Hart et al ).…”