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Lancet dynamics in greater horseshoe bats, Rhinolophus ferrumequinum.

He W, Pedersen SC, Gupta AK, Simmons JA, Müller R - PLoS ONE (2015)

Bottom Line: Echolocating greater horseshoe bats (Rhinolophus ferrumequinum) emit their biosonar pulses nasally, through nostrils surrounded by fleshy appendages ('noseleaves') that diffract the outgoing ultrasonic waves.The broadcast beam shapes were found to be altered substantially by the observed small lancet movements.These findings demonstrate that-in addition to the previously described motions of the anterior leaf and the pinna-horseshoe bat biosonar has a third degree of freedom for fast changes that can happen on the time scale of the emitted pulses or the returning echoes and could provide a dynamic mechanism for the encoding of sensory information.

View Article: PubMed Central - PubMed

Affiliation: SDU-VT International Laboratory, School of Physics, Shandong University, Jinan, Shandong, China.

ABSTRACT
Echolocating greater horseshoe bats (Rhinolophus ferrumequinum) emit their biosonar pulses nasally, through nostrils surrounded by fleshy appendages ('noseleaves') that diffract the outgoing ultrasonic waves. Movements of one noseleaf part, the lancet, were measured in live bats using two synchronized high speed video cameras with 3D stereo reconstruction, and synchronized with pulse emissions recorded by an ultrasonic microphone. During individual broadcasts, the lancet briefly flicks forward (flexion) and is then restored to its original position. This forward motion lasts tens of milliseconds and increases the curvature of the affected noseleaf surfaces. Approximately 90% of the maximum displacements occurred within the duration of individual pulses, with 70% occurring towards the end. Similar lancet motions were not observed between individual pulses in a sequence of broadcasts. Velocities of the lancet motion were too small to induce Doppler shifts of a biologically-meaningful magnitude, but the maximum displacements were significant in comparison with the overall size of the lancet and the ultrasonic wavelengths. Three finite element models were made from micro-CT scans of the noseleaf post mortem to investigate the acoustic effects of lancet displacement. The broadcast beam shapes were found to be altered substantially by the observed small lancet movements. These findings demonstrate that-in addition to the previously described motions of the anterior leaf and the pinna-horseshoe bat biosonar has a third degree of freedom for fast changes that can happen on the time scale of the emitted pulses or the returning echoes and could provide a dynamic mechanism for the encoding of sensory information.

No MeSH data available.


Related in: MedlinePlus

Numerical beampattern estimates obtained for the lancet rotation in the noseleaf model derived from specimen female 1.Each row represents a different orientation of the lancet from complete extension (posterior, 0°, top row) to the maximum flexion studied (anterior, 12°, bottom row). The columns correspond to different frequencies (60 kHz to 80 kHz). The level for the single contour line shown is -3 dB. The gray-level coding of the amplitude values is linear.
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pone.0121700.g006: Numerical beampattern estimates obtained for the lancet rotation in the noseleaf model derived from specimen female 1.Each row represents a different orientation of the lancet from complete extension (posterior, 0°, top row) to the maximum flexion studied (anterior, 12°, bottom row). The columns correspond to different frequencies (60 kHz to 80 kHz). The level for the single contour line shown is -3 dB. The gray-level coding of the amplitude values is linear.

Mentions: We hypothesized that the bending of the lancet might be used by horseshoe bats to actively control their spatial emission beampatterns in order to reallocate ultrasonic energy over space and time, possibly to enhance the encoding of sensory information that is of particular interest to the animals. To test this hypothesis, we employed three-dimensional digital surface mesh models of horseshoe bat noseleaf shapes derived from micro-CT scans of three individual bats (two males and one female) and rotated the lancet of the models from an initial upright position to a rotation of 12° in steps of 4° (see Fig. 1ii). For each individual 3D model, with its particular rotated version of the lancet, the resulting emission beampatterns were determined using finite element methods. Frequencies of 60, 65, 70, 75, and 80 kHz were tested to provide a representative sample of the frequency range covered by the bat’s broadcasts (60–78 kHz). The numerical beampattern predictions (see Figs. 4, 5, 6) showed profound changes in the beampattern in response to the rotations of the lancet. In general, forward rotation of the lancet resulted in emission beams that extended over a larger angle in elevation, either through a wider mainlobe or through the addition of sidelobes as is evident throughout the numerical beampattern estimates obtained for all three noseleaf models studied (see Figs. 4, 5, 6). However, besides these large-scale changes in beampattern geometry, lancet rotation also led to beampattern changes that occurred on a smaller scale, but had nevertheless a large impact on the local beampattern gain values. The prevalence of such local effects with large impacts on the beamgain is evident from the differences between the beampatterns obtained for different lancet rotations (see Fig. 7). Subtracting beampatterns obtained for the different lancet rotations studied from the beampatterns obtained for the upright lancet showed numerous local changes (see Fig. 7) with changes in beampattern gain around 10 dB not being uncommon. The prevalence of such large gain changes increased with increasing rotation of the lancet away from the upright position.


Lancet dynamics in greater horseshoe bats, Rhinolophus ferrumequinum.

He W, Pedersen SC, Gupta AK, Simmons JA, Müller R - PLoS ONE (2015)

Numerical beampattern estimates obtained for the lancet rotation in the noseleaf model derived from specimen female 1.Each row represents a different orientation of the lancet from complete extension (posterior, 0°, top row) to the maximum flexion studied (anterior, 12°, bottom row). The columns correspond to different frequencies (60 kHz to 80 kHz). The level for the single contour line shown is -3 dB. The gray-level coding of the amplitude values is linear.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390203&req=5

pone.0121700.g006: Numerical beampattern estimates obtained for the lancet rotation in the noseleaf model derived from specimen female 1.Each row represents a different orientation of the lancet from complete extension (posterior, 0°, top row) to the maximum flexion studied (anterior, 12°, bottom row). The columns correspond to different frequencies (60 kHz to 80 kHz). The level for the single contour line shown is -3 dB. The gray-level coding of the amplitude values is linear.
Mentions: We hypothesized that the bending of the lancet might be used by horseshoe bats to actively control their spatial emission beampatterns in order to reallocate ultrasonic energy over space and time, possibly to enhance the encoding of sensory information that is of particular interest to the animals. To test this hypothesis, we employed three-dimensional digital surface mesh models of horseshoe bat noseleaf shapes derived from micro-CT scans of three individual bats (two males and one female) and rotated the lancet of the models from an initial upright position to a rotation of 12° in steps of 4° (see Fig. 1ii). For each individual 3D model, with its particular rotated version of the lancet, the resulting emission beampatterns were determined using finite element methods. Frequencies of 60, 65, 70, 75, and 80 kHz were tested to provide a representative sample of the frequency range covered by the bat’s broadcasts (60–78 kHz). The numerical beampattern predictions (see Figs. 4, 5, 6) showed profound changes in the beampattern in response to the rotations of the lancet. In general, forward rotation of the lancet resulted in emission beams that extended over a larger angle in elevation, either through a wider mainlobe or through the addition of sidelobes as is evident throughout the numerical beampattern estimates obtained for all three noseleaf models studied (see Figs. 4, 5, 6). However, besides these large-scale changes in beampattern geometry, lancet rotation also led to beampattern changes that occurred on a smaller scale, but had nevertheless a large impact on the local beampattern gain values. The prevalence of such local effects with large impacts on the beamgain is evident from the differences between the beampatterns obtained for different lancet rotations (see Fig. 7). Subtracting beampatterns obtained for the different lancet rotations studied from the beampatterns obtained for the upright lancet showed numerous local changes (see Fig. 7) with changes in beampattern gain around 10 dB not being uncommon. The prevalence of such large gain changes increased with increasing rotation of the lancet away from the upright position.

Bottom Line: Echolocating greater horseshoe bats (Rhinolophus ferrumequinum) emit their biosonar pulses nasally, through nostrils surrounded by fleshy appendages ('noseleaves') that diffract the outgoing ultrasonic waves.The broadcast beam shapes were found to be altered substantially by the observed small lancet movements.These findings demonstrate that-in addition to the previously described motions of the anterior leaf and the pinna-horseshoe bat biosonar has a third degree of freedom for fast changes that can happen on the time scale of the emitted pulses or the returning echoes and could provide a dynamic mechanism for the encoding of sensory information.

View Article: PubMed Central - PubMed

Affiliation: SDU-VT International Laboratory, School of Physics, Shandong University, Jinan, Shandong, China.

ABSTRACT
Echolocating greater horseshoe bats (Rhinolophus ferrumequinum) emit their biosonar pulses nasally, through nostrils surrounded by fleshy appendages ('noseleaves') that diffract the outgoing ultrasonic waves. Movements of one noseleaf part, the lancet, were measured in live bats using two synchronized high speed video cameras with 3D stereo reconstruction, and synchronized with pulse emissions recorded by an ultrasonic microphone. During individual broadcasts, the lancet briefly flicks forward (flexion) and is then restored to its original position. This forward motion lasts tens of milliseconds and increases the curvature of the affected noseleaf surfaces. Approximately 90% of the maximum displacements occurred within the duration of individual pulses, with 70% occurring towards the end. Similar lancet motions were not observed between individual pulses in a sequence of broadcasts. Velocities of the lancet motion were too small to induce Doppler shifts of a biologically-meaningful magnitude, but the maximum displacements were significant in comparison with the overall size of the lancet and the ultrasonic wavelengths. Three finite element models were made from micro-CT scans of the noseleaf post mortem to investigate the acoustic effects of lancet displacement. The broadcast beam shapes were found to be altered substantially by the observed small lancet movements. These findings demonstrate that-in addition to the previously described motions of the anterior leaf and the pinna-horseshoe bat biosonar has a third degree of freedom for fast changes that can happen on the time scale of the emitted pulses or the returning echoes and could provide a dynamic mechanism for the encoding of sensory information.

No MeSH data available.


Related in: MedlinePlus