Abstract
Previous studies of magnetoreception in honey bees, Apis mellifera, focused on the identification of magnetic material, its formation, the location of the receptor and potential underlying sensory mechanisms, but never directly linked magnetic material to a magnetoreceptive function. In our study, we demonstrate that ferromagnetic material consistent with magnetite plays an integral role in the bees' magnetoreceptor. Subjecting lyophilized and pelletized bee tagmata to analyses by a superconducting quantum interference device generated a distinct hysteresis loop for the abdomen but not for the thorax or the head of bees, indicating the presence of ferromagnetic material in the bee abdomen. Magnetic remanence of abdomen pellets produced from bees that were, or were not, exposed to the 2.2-kOe field of a magnet while alive differed, indicating that magnet exposure altered the magnetization of this magnetite in live bees. In behavioural two-choice field experiments, bees briefly exposed to the same magnet, but not sham-treated control bees, failed to sense a custom-generated magnetic anomaly, indicating that magnet exposure had rendered the bees' magnetoreceptor dysfunctional. Our data support the conclusion that honey bees possess a magnetite-based magnetoreceptor located in the abdomen.
Highlights
Magnetoreception is widespread among animals, including vertebrates, insects and even microorganisms [15]
In superconducting quantum interference device (SQUID) experiments, we show that the abdomen but not the head or the thorax of honey bees contains ferromagnetic material consistent with being magnetite, and for which remanent magnetization can be demonstrated
Previous studies of magnetoreception in honey bees have addressed the location of the magnetoreceptor [44,50,51,52,53], its formation [51,52] and potential mechanisms for encoding the direction and intensity of themagnetic field [31,50,52,54]
Summary
Magnetoreception (the sensory modality that enables organisms to detect magnetic fields) is widespread among animals, including vertebrates (mammals [1,2], birds [3,4], fishes [5,6,7], reptiles [8,9]), insects (e.g. monarch butterflies [10], beetles [11], bees [12 –14]) and even microorganisms [15]. Apis mellifera, are good model organisms for locating and characterizing a magnetoreceptor because they (i) use the geomagnetic field for orientation during foraging [14,41] and for alignment of their combs [42], (ii) detect small magnetic anomalies relative to the geomagnetic background [43], (iii) distinguish between magnetic anomalies in behavioural experiments [14] and (iv) can readily be obtained from large hives for laboratory analyses and field testing. One could attempt to impair or modify the magnetoreceptor by applying sufficiently intense magnetic fields, and bioassaying the subsequent behaviour of treated honey bees This principle was elegantly demonstrated by Wiltschko et al [45,46], who re-magnetized ferromagnetic material in the beaks of pigeons and Australian silvereyes and thereby temporarily altered the migratory direction of such treated birds. For two-choice bioassays, we used a Pearson’s x2-test to evaluate the significance of deviations from a discrete random equal probability distribution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
