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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 resonance linewidth and anisotropy fields of the broad resonance lines (HF) of purified IGs. (A) Temperature dependence of the resonance linewidth of the HF. The solid line is the best fit of the HF data according to Eq. 1, with ΔH0 = 1791±37 Oe and ΔE/2kB = 50.8±2.6 K. (B) Temperature dependence of the resonance field of HF and LF. Note that the HF and LF curves are almost parallel to each other, with the field shifting by an average value of about 2496±50 Oe. (C) Anisotropy fields calculated from the resonant field's values, using Eq. 2 for the HF lines.
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pone-0000395-g006: The resonance linewidth and anisotropy fields of the broad resonance lines (HF) of purified IGs. (A) Temperature dependence of the resonance linewidth of the HF. The solid line is the best fit of the HF data according to Eq. 1, with ΔH0 = 1791±37 Oe and ΔE/2kB = 50.8±2.6 K. (B) Temperature dependence of the resonance field of HF and LF. Note that the HF and LF curves are almost parallel to each other, with the field shifting by an average value of about 2496±50 Oe. (C) Anisotropy fields calculated from the resonant field's values, using Eq. 2 for the HF lines.

Mentions: The temperature dependencies of the HF linewidth of purified IGs spectra are shown in Figure 6A. Based on the assumption of isolated spherical nanoparticles, the HF linewidths temperature dependencies are fitted using the equation 1where ΔH0 is the low temperature limit value, ΔE is the magnetic energy KV, V is the nanoparticle magnetic volume, and kB is the Boltzman constant. The solid lines in Figure 6A are the best fitting curves for ΔH0 = 1791±37 Oe and ΔE/2kB = 50.8±2.6 K, respectively. In equation 1, ΔH0 = 5gβSn/D3, the description of the prefactor ΔH0 includes the g factor (g), the Bohr magneton (β), the spin associated with each magnetic center inside the nanoparticle (S), the number of magnetic centers per particle (n), and the particle-particle distance in the matrix (D). Assuming g = 2, S = 2 [45], and n = 8.5×103 [13], we obtain D = 10±0.1 nm. An average shift of 2496±50 Oe between the two HR versus T curves of purified IGs was obtained (Figure 6B). As K is temperature-dependent, ΔE is taken as KefV with Kef = Ms(-HA)/2, where (HA) is the mean value obtained from Figure 6C (125 Oe) according to the following equation and previous studies [28], [44], [45]. 2Taking the magnetite saturation magnetization (Ms) as 470 Oe, magnetic volumes are estimated to be (0.48±0.02)×103 nm3 and correspond to mean particle diameters of 9.7±0.2 nm. The size of SM in purified IGs is consistent with SM reported by previous studies of the abdomen with SQUID [30], EPR [29] and HRTEM [13]. However, larger magnetite nanoparticles (30 nm or more) were reported to be present in the abdomens of honeybees by SQUID [47]. More studies are needed to clarify the size of magnetite in the abdomen of honeybees.


Magnetoreception system in honeybees (Apis mellifera).

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

The resonance linewidth and anisotropy fields of the broad resonance lines (HF) of purified IGs. (A) Temperature dependence of the resonance linewidth of the HF. The solid line is the best fit of the HF data according to Eq. 1, with ΔH0 = 1791±37 Oe and ΔE/2kB = 50.8±2.6 K. (B) Temperature dependence of the resonance field of HF and LF. Note that the HF and LF curves are almost parallel to each other, with the field shifting by an average value of about 2496±50 Oe. (C) Anisotropy fields calculated from the resonant field's values, using Eq. 2 for the HF lines.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1851986&req=5

pone-0000395-g006: The resonance linewidth and anisotropy fields of the broad resonance lines (HF) of purified IGs. (A) Temperature dependence of the resonance linewidth of the HF. The solid line is the best fit of the HF data according to Eq. 1, with ΔH0 = 1791±37 Oe and ΔE/2kB = 50.8±2.6 K. (B) Temperature dependence of the resonance field of HF and LF. Note that the HF and LF curves are almost parallel to each other, with the field shifting by an average value of about 2496±50 Oe. (C) Anisotropy fields calculated from the resonant field's values, using Eq. 2 for the HF lines.
Mentions: The temperature dependencies of the HF linewidth of purified IGs spectra are shown in Figure 6A. Based on the assumption of isolated spherical nanoparticles, the HF linewidths temperature dependencies are fitted using the equation 1where ΔH0 is the low temperature limit value, ΔE is the magnetic energy KV, V is the nanoparticle magnetic volume, and kB is the Boltzman constant. The solid lines in Figure 6A are the best fitting curves for ΔH0 = 1791±37 Oe and ΔE/2kB = 50.8±2.6 K, respectively. In equation 1, ΔH0 = 5gβSn/D3, the description of the prefactor ΔH0 includes the g factor (g), the Bohr magneton (β), the spin associated with each magnetic center inside the nanoparticle (S), the number of magnetic centers per particle (n), and the particle-particle distance in the matrix (D). Assuming g = 2, S = 2 [45], and n = 8.5×103 [13], we obtain D = 10±0.1 nm. An average shift of 2496±50 Oe between the two HR versus T curves of purified IGs was obtained (Figure 6B). As K is temperature-dependent, ΔE is taken as KefV with Kef = Ms(-HA)/2, where (HA) is the mean value obtained from Figure 6C (125 Oe) according to the following equation and previous studies [28], [44], [45]. 2Taking the magnetite saturation magnetization (Ms) as 470 Oe, magnetic volumes are estimated to be (0.48±0.02)×103 nm3 and correspond to mean particle diameters of 9.7±0.2 nm. The size of SM in purified IGs is consistent with SM reported by previous studies of the abdomen with SQUID [30], EPR [29] and HRTEM [13]. However, larger magnetite nanoparticles (30 nm or more) were reported to be present in the abdomens of honeybees by SQUID [47]. More studies are needed to clarify the size of magnetite in the abdomen of honeybees.

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