Magnetômetro 'natural' na parte superior do bico de aves?

sexta-feira, fevereiro 26, 2010

Natural 'Magnetometer' in Upper Beak of Birds?

ScienceDaily (Feb. 26, 2010) — Iron containing short nerve branches in the upper beak of birds may serve as a magnetometer to measure the vector of the Earth magnetic field (intensity and inclination) and not only as a magnetic compass, which shows the direction of the magnetic field lines. Several years ago, the Frankfurt neurobiologists Dr. Gerta Fleissner and her husband Prof. Dr. Günther Fleissner discovered these structures in homing pigeons and have, in close cooperation with the experimental physicist Dr. Gerald Falkenberg (DESY Hamburg), characterized the essential iron oxides.

Homing pigeon. (Credit: iStockphoto/Andrzej Podulka)

"After we had shown the system of dendrites with distinct subcellular iron-containing compartments in homing pigeons, immediately the question was posed whether similar dendritic systems may be found in other bird species, too," as Gerta Fleissner, the principal investigator, comments. Meanwhile they could describe similar candidate structures in the beaks of various avian species. X-Ray-fluorescence measurements at DESY demonstrated that the iron oxides within these nervous dendrites are identical. These findings were published few days ago in the high-ranking interdisciplinary online journal Plos One.

More than about 500 dendrites in the periphery encode the magnetic field information, which is composed in the central nervous system to a magnetic map. It obviously does not matter, whether birds use this magnetic map for their long distance orientation or do not -- the equipment can be found in migratory birds, like robin and garden warbler, and well as in domestic chicken. "This finding is astonishing, as the birds studied have a different life styles and must fulfil diverse orientational tasks: Homing pigeons, trained to return from different release sites to their homeloft, short-distance migrants like robins, long-distance migratory birds like garden warblers and also extreme residents like domestic chicken," explains Gerta Fleissner.

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Avian Magnetoreception: Elaborate Iron Mineral Containing Dendrites in the Upper Beak Seem to Be a Common Feature of Birds

Gerald Falkenberg1, Gerta Fleissner2*, Kirsten Schuchardt2,Markus Kuehbacher3, Peter Thalau2, Henrik Mouritsen4,Dominik Heyers4, Gerd Wellenreuther1, Guenther Fleissner2

1 Hamburger Synchrotronstrahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany, 2 Institut für Zellbiologie und Neurowissenschaften, Goethe-Universität, Frankfurt a. M., Germany, 3 Abt. Elementanalytik, Helmholtz Centre Berlin for Materials and Energy, Berlin, Germany, 4 Institut für Biologie und Umweltwissenschaften, Carl von Ossietzky-Universität, Oldenburg, Germany

Abstract Top

The magnetic field sensors enabling birds to extract orientational information from the Earth's magnetic field have remained enigmatic. Our previously published results from homing pigeons have made us suggest that the iron containing sensory dendrites in the inner dermal lining of the upper beak are a candidate structure for such an avian magnetometer system. Here we show that similar structures occur in two species of migratory birds (garden warbler, Sylvia borin and European robin, Erithacus rubecula) and a non-migratory bird, the domestic chicken (Gallus gallus). In all these bird species, histological data have revealed dendrites of similar shape and size, all containing iron minerals within distinct subcellular compartments of nervous terminals of the median branch of the Nervus ophthalmicus. We also used microscopic X-ray absorption spectroscopy analyses to identify the involved iron minerals to be almost completely Fe III-oxides. Magnetite (Fe II/III) may also occur in these structures, but not as a major Fe constituent. Our data suggest that this complex dendritic system in the beak is a common feature of birds, and that it may form an essential sensory basis for the evolution of at least certain types of magnetic field guided behavior.

Citation: Falkenberg G, Fleissner G, Schuchardt K, Kuehbacher M, Thalau P, et al. (2010) Avian Magnetoreception: Elaborate Iron Mineral Containing Dendrites in the Upper Beak Seem to Be a Common Feature of Birds. PLoS ONE 5(2): e9231. doi:10.1371/journal.pone.0009231

Editor: Eric Warrant, Lund University, Sweden

Received: August 13, 2009; Accepted: January 25, 2010; Published: February 16, 2010

Copyright: © 2010 Falkenberg et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: The project is supported by grants from the Deutsche Forschungsgemeinschaft (Fl 177/15-1 and 16-1),; from HASYLAB at DESY, Hamburg (I-05-095, II-20060167),; from the Stiftung Polytechnische Gesellschaft, Frankfurt a. M.,; from the Gemeinnützige Hertie-Stiftung, Berlin: ZEN-program,; from the Alumni of the Goethe-University, Frankfurt a. M.,; from the Volkswagenstiftung (Heisenberg-Professorship to H.M.), The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

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