Scientists have an answer to how fish can detect sound

Music and the neurological basis of erection in asexuality and sexual behaviours in humans (and the role of the penis and clitoris)

150 years after they were discovered, researchers have identified how the penis and clitoris work. There was little known about how these structures work or their role in sex, despite being similar to touch-activated structures on people’s fingers and hands. Experiments done in mice show that low-frequency music caused sexual behaviours such as erections in both males and females. The research team hopes that they can uncover the neurological basis of certain sexual problems.

The identity of a mysterious object and how genes are edited to make rice plants more water-efficient are not yet known.

Fish acoustics stimulated by facing speakers in a waterproof enclosure: Phase reconstruction and observable correlations in audio stimulation and motion reconstruction

The fish was acoustically stimulated using two facing speakers sealed in custom-made waterproof enclosures. The diaphragms were exposed to water. The speakers were each placed about 1.3 cm away from the fish. They were driven using a DAQ card (National Instruments USB-6211), connected through audio amplifiers (Kemo M031N, 3.5 W). There was pressure of up to approximately 1 Pa in the fish position in the pressure-only configuration and up to 8 s1 in the particle motion-only configuration, suggesting the expected correlation between pressure and motion.

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The acoustic stimulation cycle had different phases and each pixel had been probed at a different phase. As sound propagates while scanning two consecutive pixels, the probed acoustic phase is shifted by (2{\rm{\pi }}\times {\rm{pixelPeriod}}), which was taken into account in the motion reconstruction of the imaged structures (Extended Data Fig. 10c). These images were then turned into a dataset for Nx,Ny,nStep.

The Shannon–Nyquist sampling Theorem requires us to measure the total number of phases for the reconstruction of the object’s motion. We used four phases to ensure proper phase reconstruction, as noise can affect this measurement.

Laser-scanning two-photon microscope for vibrometric imaging of aquatic fish. Application to neomycin-treated fish

The principle of laser-scanner vibrometric measurement is shown 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)

Fish were given a dose of 120,000,000 l1 of fish water-buffered from the MS-222. They were subsequently placed on a preformed agarose mould, which allowed the gill covers to move freely, and immobilized with 2% low-melting-point agarose (melting point 25 °C). The aquarium water was administered through a glass capillary in their mouth.

The confocal reflectance microscope was based on a custom-built laser-scanning two-photon microscope (Extended Data Fig. 10a). The illumination source was not a normal laser, but a Ti:sapphire laser. Before entering a laser-scanning two-photon microscope, the beam passed through a 90:10 beam splitter (90% reflection, 10% transmission). The light back-scattered by the fish inner structures was descanned, reflected by the 90:10 beam splitter and then focused by a lens into a single-mode fibre. A custom-written software was used to control the microscope.

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. Afterwards, they were transferred to a beaker with tank water. After 30 min, behavioral experiments began. To confirm the reliability of the lateral line ablation protocol, we stained 30 neomycin-treated fish. 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 with an ice shock and imaged with an epifluorescence microscope. The stained brain was different in the control fish and the neomycin-treated fish. For example, 9e,f for images. 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. After being washed in PBS for 15 min, the fish was given a solution of 5% sigma Aldrich to be stained with in PBS at 4 C. The fish was washed in PBS for 15 minutes before being put in a cryo tube. The micro-CT scan was carried out at the ANATOMIX beamline at SOLEIL synchrotron by XPLORAYTION. The sample was put into a white X-ray beam. A digital camera with a sensor size of 6.5 m and an effective pixel size of 0.6500 m was used in a scans consisting of 3,200 projections. The registered data were binned to 1.2970 µm voxel size. Key structures of the hearing apparatus were manually segmented. Planes were hand-labelled with 3D Slicer 76 (v5.6) and then interpolated using Biomedisa. It is possible to convert between different file types. The segments were turned into mesh grids and loaded into Blender for cleaning and rendering.

bias towards trials and fish For each stimulus or set of stimuli, startle trials were pooled across all fish, and the fraction of startles in one direction was calculated. Using the two-sided binomial test, we calculated how likely a measured directional bias (approach or escape) would have been observed if the response was unbiased.

The swimming behavior of D. cerebrum was tracked using a Pose Tracking tool. A skeleton of seven equidistant dots along the body segments of the male and female fish were hand-coded with a code that stood for eyes, in 140 frames across nine recordings. For training, the single animal model was used. The model parameters and the trained model are available at the G-Node repository (see Data availability).

The experiment setup consisted of a 10 cm by 10 cm tank with a thin sheet wall and speaker’s enclosures surrounded by plastic folders. The fish were confined between the speakers and the speakers were shielded from the fish in the inner tank. 1a,b). The height of the water was 10 cm, and the transparent bottom of the inner tank was at 6.3 cm, leaving 3.7 cm to the water surface as a water column for the fish to swim in. The speakers were level with this water column, and all sounds were targeted for this water column. Infrared light-emitting diodes illuminated the fish from below. Live tracking of the fish was carried out on a portion of frames at 15 frames per second, and the inner tank was filmed with an overhead camera at 120 frames per second. White light-emitting diodes lit the setup indirectly via reflections from the room walls. The room and water temperature was kept at 27 °C.

All animal experiments conformed to Berlin state, German federal and European Union animal welfare regulations and were approved by the LAGeSo, the Berlin authority for animal experiments. The water parameters for the fish were as follows: pH 7.3, temperature 27 C. The adult fish were between 4 and 11 months of age.

Source: The mechanism for directional hearing in fish

Computation of particle acceleration to a sound monopole with a single frame Scan Trigger applied separately for the discrete Fourier transform and the galvanometric scanning mirrors

To compute the particle acceleration ({a}{r}(r,t)) at a distance (r) to a sound monopole with pressure (p(r,t)) for discrete signals of arbitrary waveform, we applied this equation separately for each Fourier component. Given a pressure waveform ({{{\bf{p}}}{n}}\,:={p}{0}{,p}{1},\cdots ,{p}{N-1}) with (N) samples ({p}{n}), spaced at (T=1/{sr}) with sample rate ({sr}), the particle acceleration ({{{\bf{a}}}{n}}\,:={a}{0}{,a}{1},\cdots ,{a}{N-1}) that would be observed at a distance (r={r}{0}) from a sound monopole was calculated by carrying out the discrete Fourier transform ({{{\bf{P}}}{l}}\,:={P}{0}{,P}{1},\cdots ,{P}_{N-1})

This will add constraints to the various scanning parameters. The data presented in fig was used with the help of both f_rmscan and f_rmstim.

The acoustic stimulation and galvanometric scanning mirrors had to be synchronized in order to ensure the best possible sound recordings for each measurement. The sound generation was achieved using each single frame Scan Trigger.

In the section entitled Sound stimulation, we tell you how we defined the pressure and particle motion targets that were conditioned.

Waves, wavelength, and speed of sound are included.

The radial particle velocity decays linearly with distance in the near field in a medium of density.

By contrast, particle speed can be adjusted by the amount of distance from nearby sounds (rll 1).

Source: The mechanism for directional hearing in fish

Sound stimulation of a hydrophone in the inner tank: x and y accelerations measured by the indirect method and the inverse Fourier transform

To create the same sounds at any position inside the inner tank, impulse responses for all 4 speakers were measured across 25 positions on a 5 × 5 grid with 1.5-cm spacing. In the following, the sound targeting method is described for one position.

Hence, in all experiments, x and y acceleration were measured through the indirect method, on the basis of spatial pressure gradients. The particle acceleration sensor still proved useful in measuring the vertical z acceleration in our setup.

Whereas hydrophones are manufactured and calibrated for underwater use, the particle acceleration sensor is not made to measure particle acceleration underwater and is meant to be glued onto the vibrating object. Owing to an acoustic impedance mismatch between metal and water, we expected the PCB sensor to underestimate particle acceleration.

We found that the x and y accelerations obtained from the direct method were indistinguishable from the x and y waveforms obtained through the indirect method. The validity of the approximation in the indirect method is confirmed by a close match.

The method for sound stimulation is based upon the components of the target waveforms. The time-domain signal for the ith speaker is then given by the inverse Fourier transform using components ({S}_{i,l}).

mathopsum :limits_i,p ast s_i

Source: The mechanism for directional hearing in fish

Effects of Pressure Inversion on the Dynamic Behavior of a Trick Configuration in a Single-Speaker Speaker Configuration for Two-Step Sound Conditioning

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. The signals were fixed to look like the single-speaker signal and only the activations of the two speakers along the orthogonal axis were conditioned.