Fishers can independently detect pressure and particle motion based on Krause corpuscles in the penis and clitoris of rice plants
Researchers found nerve-cell structures on the penis and clitoris 150 years after they were discovered. There was little knowledge about how the structures worked, or their role in sex. Working in mice, a team found that Krause corpuscles in both male and females were activated when exposed to low-frequency vibrations and caused sexual behaviours like erections. The researchers hope that this work could help uncover the neurological basis underlying certain sexual dysfunctions.
The identity of a mysterious object and the possibility of editing rice plants to use less water are some of the mysteries thatAstronomers struggle to figure out.
It’s long been understood that fish can identify the direction a sound came from, but working out how they do it is a question that’s had scientists stumped for years. Now using a specialist set-up, a team of researchers have demonstrated that some fish can independently detect two components of a sound wave — pressure and particle motion — and combine this information to identify where a sound comes from.
Studying the motion of inner structures of fish with the PIVlab80 vibrometric imaging system (Extended Data Fig. 10b(i))
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We used the PIVlab80 to study the motion of the inner structures of fish, because it was developed to study the motion of flowing particles. Essentially, the particle displacement is assessed by cross-correlating subregions with decreasing sizes of consecutive images (Extended Data Fig. 10b(v)). The contrast of the reflectance images was enhanced before the displacement analysis, and the results were curated in post-processing by removing outliers and interpolating detection gaps.
We needed to measure the objects under multiple phases to reconstruct their motion. We use four phase steps to ensure proper phase reconstruction and keep acquisition sessions short.
The principle of the laser-scanning vibrometric measurement is illustrated in Fig. 3b and Extended Data Fig. 10b. The sample (Extended Data Fig. 10b(i)) was stimulated with an acoustic sinusoidal wave at frequency ({f}{{\rm{stim}}}), and imaged with a laser-scanning microscope with a line rate ({f}{{\rm{scan}}}) (Extended Data Fig. 10b(ii)
Source: The mechanism for directional hearing in fish
Fluorescence microscopy of fish with a laser-scanning confocal reflectance microscope: effects of neomycin and neuromast ablation
The fish were injected in a small amount of water. The gill covers were placed on a preformed agarose mold which let them move freely, and then immobilized with 2% low-melting-point agarose. A flow of aerated aquarium water was delivered to their mouth using a glass capillary.
The confocal reflectance microscope was based on a custom-built laser-scanning two-photon microscope (Extended Data Fig. 10a). The laser was not mode-locked, and it was the illumination source. The beam passed through a beam splitter before it entered the microscope. The light back-scattered by the fish inner structures was descanned, reflected by the 90:10 beam splitter, and then focused by a lens (f = 50 mm) into a single-mode fibre (core diameter: 25 µm, numerical aperture: 0.1) acting as a confocal pinhole. The microscope was controlled by a custom-written software.
To rule out that the lateral line organ senses sound directionality in our experiments, we ablated the lateral line using neomycin79. To ablate the neuromasts, fish were placed in a 200 µM neomycin solution for about 30 min. They were put in a beaker with tank water. Behavioural experiments started after ≥30 min. The fish were stained with neomycin to confirm the reliability of the protocol. After the behaviour experiment, they were transferred to a 100 µM DASPEI (2-[4-(dimethylamino)styryl]-1-ethylpyridinium iodide) solution and then to a beaker with tank water to wash out unbound DASPEI. Afterwards the fish were euthanized and imaged with a microscope. There were reliably stained tumors in control fish but not in neomycin-treated fish. For images, 9e,f. As functional metrics we report an increase in number of wall contacts after startles (Extended Data Fig. 9g) and a decrease in foraging strikes in the dark (Extended Data Fig. 9h) in neomycin-treated fish.
A 12-month-old male wild-type D. cerebrum was euthanized by ice shock and fixed with 4% paraformaldehyde in phosphate-buffered saline (PBS) at 4 °C overnight. The next day, the fish was washed for 15 min in PBS before being stained with 5% phosphomolybdic acid (Sigma Aldrich) solution in PBS at 4 °C overnight. After staining, the fish was washed in PBS for fifteen minutes before being deposited in a cryo tube. The micro-CT scan was carried out at the ANATOMIX beamline at SOLEIL synchrotron by XPLORAYTION. The sample was placed in a white X-ray beam. A digital camera with a sensor size of 6.5 m and an effective screen size of 0.6485 m was used for a large Scan that consisted of 3,200 projections taken at about 10 optical magnification. The data was sized to 1.2970 m. The hearing apparatus had key structures manually broken down. Planes were hand-labelled using 3D Slicer 76, and then put in a blend using Biomedisa (v23)77. There were different file types used for the conversion. The segments were turned into mesh grids and loaded into Blender for cleaning and rendering.
The x–y position of the fish was detected by the experiment, and the loading for the speakers was linearly adjusted on the basis of sounds next to the grid positions.
The swimming behavior of D. cerebrum was tracked with a Pose Tracking tool. In total, 140 frames across nine random recordings of male and female fish were hand-labelled with a skeleton consisting of 7 equidistant nodes along the fish’s body segments and 2 additional nodes, 1 for each eye. The single animal model was used for training. The model parameters and the trained model are available at the G-Node repository (see Data availability).
Each fish was tested once, and one fish was tested at a time. In the first minutes of the recording, a 10 cm × 10 cm acrylic plate with centimetre markings was placed in the inner tank to match the sound calibration grid to the video frame. After three minutes, the fish were in the inner tank.
The LAGe So, the authority for animal experiments in Berlin, approved all animal experiments that conformed to the rules of the German federal and European Union. D. cerebrum were kept in commercial zebrafish aquaria (Tecniplast) with the following water parameters: pH 7.3, conductivity 350 µS cm−1, temperature 27 °C. We used male and female fish from 4 to 11 months.
Source: The mechanism for directional hearing in fish
Volumetric Investigation of the Pressure Response of the Inner Structures to the Acoustic Stimulation in a Two-Dimensional Water Vapor
and deriving particle acceleration for each Fourier component ({{{\bf{A}}}{l}}\,:=\,{A}{0}{,A}{1},\cdots ,{A}{N-1}) independently. With corresponding frequencies. L/ ( NT) such that (k\approx 2\pi l/({NTc})), and the relationship between pressure and particle acceleration, ({A}_{l}), is calculated as
This in turn set additional constraints on the various scanning parameters. For the data presented in Figure, we used the following methods: (f_rmstim=mathrm1,000)
The motion detection yielded x- and y-displacement maps at each of the four phases in the acoustic stimulation period. The first Fourier component was used to derive the amplitude and phase of the local displacement. The phase was corrected for being offset along the horizontal x direction by a line scanning procedure. Owing to the synchronization of the acoustic stimulation with the line scanning process, we could carry out this measurement in several planes and obtain a consistent volumetric complex map characterizing the motion response of the various inner structures to the acoustic stimulation. The two-dimensional phase maps show the projected motion along the speaker–speaker axis and the projected motion to the speaker–speaker axis.
When dropping a rubber piece into the water, we saw that D. cerebrum startedle. The pressure of this sound was recorded at a high-pass and we used a 12-ms sample to serve as our pressure waveform template. The peak sound pressure was set to 167 decibels (or 1 Pa) by re scaling the pressure Wavelength accordingly. The small speakers were still supporting this loud sound and it was loud enough to startles. The first peak’s rise time (10% to 90% absolute amplitude) was 0.664 ms and the centre frequency of the pulse was about 780 Hz. The pressure and monopole theory used to calculate the target horizontal particle acceleration were as follows.
There is a wavenumber, speed of sound andomega -2rmpi f.
In a medium of density (\rho ), the radial particle velocity decays quadratically with distance in the near field (({kr}\ll 1), limit dependent on frequency):
By contrast, particle acceleration—the temporal derivative of particle velocity—decays quadratically with distance for nearby sounds ((r\ll 1), limit independent of frequency):
In the second method, particle acceleration was measured along all three axes, with an acceleration sensor owned by PCB Piezotronics and used by National Instruments. 1d Like the hydrophone, the acceleration sensor was moved across all 5 × 5 grid positions during repeated playback of the same sound, giving measurements for x, y and z acceleration.
Particles were measured indirectly through the pressure gradient. The second law of motion is a pressure gradient force.
The particle acceleration sensor is meant to be used on a vibrating object, not on a swimming pool, and it’s not made to measure underwater particle acceleration. The PCB sensor was expected to underestimate particle acceleration because of the mismatch between metal and water.
We compared x and y acceleration waveforms for both measurement methods and found that the acceleration waveforms acquired through the direct method match the waveforms acquired through the indirect method after multiplication by a factor of about 2.4. The validity of the approximation in the indirect method was confirmed by a close match.
Source: The mechanism for directional hearing in fish
Robust trick configuration of a one-dimensional speaker with a single-speaker and a two-step sound conditioning for selective pressure inversion
To increase robustness of the solutions (for example, to avoid speakers cancelling themselves unnecessarily and to limit speaker amplitude), speaker signal waveforms were forced to become similar to the target waveform. This was implemented by solving the system of equations with a least-square solver (scipy.optimize.lsq_linear) with bounds (-{B}{i,l} < {S}{i,l} < {B}_{i,l}). The absolute components of the target pressure is reanalyzed using the bound B_i,l.
P_l means mathopsum.
To ensure that the trick configuration differed from the single-speaker configuration only by selective pressure inversion, a two-step sound conditioning was carried out. The speaker signals for the single-speaker configuration were calculated first. Then, these signals were effectively fixed to closely resemble the single-speaker signal and only activations of the two speakers along the orthogonal axis were conditioned.
