EUROMAT

Magnetoreception in social insects is still poorly understood. The ferromagnetic hypothesis, proposing biomineralized magnetic nanoparticle system as the magnetic field detector, is well accepted. Evidence of magnetite/maghemite nanoparticles in the migratory ant, Pachycondyla marginata obtained by transmission electronmicroscopy (1) stimulated the use of SQUID magnetometry and ferromagnetic resonance (FMR) (2-5) to characterize magnetic materials in the body parts of other social insects. Particularly interesting is the highest magnetic material fraction found in ant antennae (42 ± 3%) and in head with antennae (66 ± 6%). This sensory part, functioning primarily as an organ of touch, could also be a magnetosensor. Under this point of view, the room temperature hysteresis curves and FMR spectra of the body parts of a fire ant, Solenopsis sp (S.s.) and a stingless bee, Schwarziana quadripunctata (S.q.) were studied. >From the magnetisation saturation values we conclude that 66 ± 2% and 67 ± 7% of the magnetic material was found in the head with antennae of S.s. and S.q., respectively. S.q. antennae contributes with 44 ± 4% of the magnetization saturation. Confirming the higher magnetic amount in these head with antennae insects, the second integral of the derivative FMR spectra yields values of 58 ± 2 % and 67 ± 4% in the of S.s. and S.q., respectively. The very similar values in the three insects are striking interesting and pointing to antennae as magnetosensors. Further experiments comprising other social insect species can elucidate this assumption. 1. D Acosta-Avalos et al. J. Exp. Biol. 202(19) (1999) 2687-92 2. DMS Esquivel et al. BioMetals 17 (4): 467-470, 2004 3. LJ El-Jaick et al. Eur Biophys J 29 (2001) 579-586 4. E Wajnberg et al. Biophys J 78(2) (2000) 1018-23 5. E Wajnberg et al. J. Magn Magn Mat 226-230 (2001) 2040-1 EUROMAT,European congress on advanced materials and processes , 5-8 Set 2005, Praga, Rep Tcheca Is Antenna the magnetosensor in social insects? D.M.S. Esquivel, O.C. Alves, G. Cernicchiaro, E. Wajnberg, H. Lins de Barros, L.G. Abraçado, M.J. Lucano