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Magnetoreception system in honeybees (Apis mellifera).

Hsu CY, Ko FY, Li CW, Fann K, Lue JT - PLoS ONE (2007)

Bottom Line: A concomitant release of calcium ion was observed by confocal microscope.The associated cytoskeleton may thus relay the magnetosignal, initiating a neural response.A model for the mechanism of magnetoreception in honeybees is proposed, which may be applicable to most, if not all, magnetotactic organisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Science, Chang Gung University, Tao-Yuan, Taiwan. hsu@mail.cgu.edu.tw

ABSTRACT
Honeybees (Apis mellifera) undergo iron biomineralization, providing the basis for magnetoreception. We showed earlier the presence of superparamagnetic magnetite in iron granules formed in honeybees, and subscribed to the notion that external magnetic fields may cause expansion or contraction of the superparamagnetic particles in an orientation-specific manner, relaying the signal via cytoskeleton (Hsu and Li 1994). In this study, we established a size-density purification procedure, with which quantitative amount of iron granules was obtained from honey bee trophocytes and characterized; the density of iron granules was determined to be 1.25 g/cm(3). While we confirmed the presence of superparamagnetic magnetite in the iron granules, we observed changes in the size of the magnetic granules in the trophycytes upon applying additional magnetic field to the cells. A concomitant release of calcium ion was observed by confocal microscope. This size fluctuation triggered the increase of intracellular Ca(+2) , which was inhibited by colchicines and latrunculin B, known to be blockers for microtubule and microfilament syntheses, respectively. The associated cytoskeleton may thus relay the magnetosignal, initiating a neural response. A model for the mechanism of magnetoreception in honeybees is proposed, which may be applicable to most, if not all, magnetotactic organisms.

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The images of increase of [Ca+2]i in the live trophocytes obtained by confocal microscope. (A) The image of trophocytes and fat cells under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (B) The image of trophocytes and fat cells labeled fluo 4 under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (C) The merge of Figure A and Figure B. Scale bar, 40 µm. (D) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□) with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪) without 1 Gauss magnetic field as control. (E) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by colchicine and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by colchicine without 1 Gauss magnetic field as control. (F) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by latrunculin B and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by latrunculin B without 1 Gauss magnetic field as control.
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pone-0000395-g005: The images of increase of [Ca+2]i in the live trophocytes obtained by confocal microscope. (A) The image of trophocytes and fat cells under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (B) The image of trophocytes and fat cells labeled fluo 4 under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (C) The merge of Figure A and Figure B. Scale bar, 40 µm. (D) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□) with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪) without 1 Gauss magnetic field as control. (E) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by colchicine and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by colchicine without 1 Gauss magnetic field as control. (F) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by latrunculin B and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by latrunculin B without 1 Gauss magnetic field as control.

Mentions: To study signal transduction elicited by MGs for magnetoreception, the variation of calcium ion in trophocytes and fat cells labeled with flou 4 were measured under confocal microscope. Of these two types of cells, trophocytes are larger (about 75 µm in diameter) and are dark green in color, while fat cells smaller (about 30 µm in diameter) and bright green (Figure 5A and 5B), distinguishable even mixed (Figure 5C). Cells without magnetic field for about 46 seconds were used as a control, whose intracellular Ca+2 concentrations ( [Ca+2]i ) would remain constant (Figure 5D). [Ca+2]i was allowed to stay constant for about 12 sec. before the magnetic field was applied; the increases in [Ca+2]i lasted for about 34 sec (Figure 5D). By contrast, the increase of [Ca+2]i occur principally in trophocytes, only weakly in the fat cells.


Magnetoreception system in honeybees (Apis mellifera).

Hsu CY, Ko FY, Li CW, Fann K, Lue JT - PLoS ONE (2007)

The images of increase of [Ca+2]i in the live trophocytes obtained by confocal microscope. (A) The image of trophocytes and fat cells under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (B) The image of trophocytes and fat cells labeled fluo 4 under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (C) The merge of Figure A and Figure B. Scale bar, 40 µm. (D) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□) with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪) without 1 Gauss magnetic field as control. (E) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by colchicine and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by colchicine without 1 Gauss magnetic field as control. (F) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by latrunculin B and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by latrunculin B without 1 Gauss magnetic field as control.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC1851986&req=5

pone-0000395-g005: The images of increase of [Ca+2]i in the live trophocytes obtained by confocal microscope. (A) The image of trophocytes and fat cells under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (B) The image of trophocytes and fat cells labeled fluo 4 under confocal microscope. Trophocytes (arrowhead). Fat cells (arrow). Scale bar, 40 µm. (C) The merge of Figure A and Figure B. Scale bar, 40 µm. (D) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□) with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪) without 1 Gauss magnetic field as control. (E) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by colchicine and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by colchicine without 1 Gauss magnetic field as control. (F) The fluorescence intensity of trophocytes (○), fat cells (Δ), and trophocytes and fat cells together (□), which is inhibited by latrunculin B and with 1 Gauss magnetic field. The fluorescence intensity of trophocytes (•), fat cells (▴) and trophocytes and fat cells together (▪), which is inhibited by latrunculin B without 1 Gauss magnetic field as control.
Mentions: To study signal transduction elicited by MGs for magnetoreception, the variation of calcium ion in trophocytes and fat cells labeled with flou 4 were measured under confocal microscope. Of these two types of cells, trophocytes are larger (about 75 µm in diameter) and are dark green in color, while fat cells smaller (about 30 µm in diameter) and bright green (Figure 5A and 5B), distinguishable even mixed (Figure 5C). Cells without magnetic field for about 46 seconds were used as a control, whose intracellular Ca+2 concentrations ( [Ca+2]i ) would remain constant (Figure 5D). [Ca+2]i was allowed to stay constant for about 12 sec. before the magnetic field was applied; the increases in [Ca+2]i lasted for about 34 sec (Figure 5D). By contrast, the increase of [Ca+2]i occur principally in trophocytes, only weakly in the fat cells.

Bottom Line: A concomitant release of calcium ion was observed by confocal microscope.The associated cytoskeleton may thus relay the magnetosignal, initiating a neural response.A model for the mechanism of magnetoreception in honeybees is proposed, which may be applicable to most, if not all, magnetotactic organisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Science, Chang Gung University, Tao-Yuan, Taiwan. hsu@mail.cgu.edu.tw

ABSTRACT
Honeybees (Apis mellifera) undergo iron biomineralization, providing the basis for magnetoreception. We showed earlier the presence of superparamagnetic magnetite in iron granules formed in honeybees, and subscribed to the notion that external magnetic fields may cause expansion or contraction of the superparamagnetic particles in an orientation-specific manner, relaying the signal via cytoskeleton (Hsu and Li 1994). In this study, we established a size-density purification procedure, with which quantitative amount of iron granules was obtained from honey bee trophocytes and characterized; the density of iron granules was determined to be 1.25 g/cm(3). While we confirmed the presence of superparamagnetic magnetite in the iron granules, we observed changes in the size of the magnetic granules in the trophycytes upon applying additional magnetic field to the cells. A concomitant release of calcium ion was observed by confocal microscope. This size fluctuation triggered the increase of intracellular Ca(+2) , which was inhibited by colchicines and latrunculin B, known to be blockers for microtubule and microfilament syntheses, respectively. The associated cytoskeleton may thus relay the magnetosignal, initiating a neural response. A model for the mechanism of magnetoreception in honeybees is proposed, which may be applicable to most, if not all, magnetotactic organisms.

Show MeSH
Related in: MedlinePlus