Biomedical subjects

Friedrich Ladich

Publications and source records attributed to Friedrich Ladich.

7 recordsLinked to original sources

PubMed2005

Hearing in fishes under noise conditions.

Our current knowledge on sound detection in fishes is mainly based on data acquired under quiet laboratory conditions. However, it is important to relate auditory thresholds to background noise in order to determine the signal-detecting abilities of animals in the natural environment. We investigated the influence of two noise levels within the naturally occurring range on the auditory sensitivity of two hearing specialists (otophysines) and a hearing generalist. Audiograms of the goldfish Carassius auratus, the lined Raphael catfish Platydoras costatus and the pumpkinseed sunfish Lepomis gibbosus (hearing generalist) were determined between 200 and 4000 Hz (100-800 Hz for L. gibbosus) under laboratory conditions and under continuous white noise by recording auditory evoked potentials (AEPs). Baseline thresholds showed greatest hearing sensitivity around 500 Hz in goldfish and catfish and at 100 Hz in the sunfish. Continuous white noise of 110 dB RMS elevated the thresholds by 15-20 dB in C. auratus and by 4-22 dB in P. costatus. White noise of 130 dB RMS elevated overall hearing thresholds significantly in the otophysines by 23-44 dB. In the goldfish, threshold did not shift at 4 kHz. In contrast, auditory thresholds in the sunfish declined only at the higher noise level by 7-11 dB. Our data show that the AEP recording technique is suitable for studying masking in fishes, and that the occurrence and degree of the threshold shift (masking) depend on the hearing sensitivity of fishes, the frequency, and noise levels tested. The results indicate that acoustic communication and orientation of fishes, in particular of hearing specialists, are limited by noise regimes in their environment.

Acoustic Stimulation↗

PubMed2005

Effects of noise exposure on click detection and the temporal resolution ability of the goldfish auditory system.

Hearing specialist fishes investigated so far revealed excellent temporal resolution abilities, enabling them to accurately process temporal patterns of sounds. Because noise is a growing environmental problem, we investigated how it affects the temporal resolution ability of goldfish. Auditory evoked potentials (AEPs) in response to clicks and double clicks were recorded before exposing, immediately after exposing the fish to white noise of 158 dB re 1 microPa for 24 h, and after 3, 7 and 14 days of recovery. Immediately after noise exposure, hearing sensitivity to clicks was reduced on average by 21 dB and recovered within 1 week. Amplitudes of the AEPs decreased by about 71% while latencies increased by 0.63 ms. Both AEP characteristics returned to baseline values within 2 weeks. Analysis of the response to double clicks showed that the minimum click period resolvable by the auditory system increased significantly from 1.25 to 2.08 ms immediately after noise exposure. After a recovery period of 3 days, this minimum period returned to pre-exposure values. The present study revealed that noise exposure affects the detection of short transient signals and the temporal resolution ability. Because acoustic information is primarily encoded via temporal patterns of sounds in fishes, environmental noise could severely impair acoustic orientation and communication.

Acoustic Stimulation↗

PubMed2004

Noise emission during the first powerboat race in an Alpine lake and potential impact on fish communities.

In order to assess the effects of high-speed boating on fish communities, noise levels were measured during the first Class 1 powerboat race on the Austrian Lake Traunsee. The noise spectra were compared to natural ambient noise and hearing abilities of four native fish species. Sound pressure levels (SPLs) were significantly elevated during the training heats and the race compared with natural levels, reaching up to 128 dB re 1 microPa (instantaneous SPL) at a distance of 300 m to the powerboats. Continuous equivalent SPLs were significantly lower during training and the pole position race compared to the race itself because fewer boats were simultaneously on the lake. The hearing abilities of the native hearing specialists and generalists were investigated. While carp and roach (two cyprinids) showed enhanced auditory sensitivity typical for hearing specialists, perch and whitefish were much less sensitive to sounds. Comparisons between power boat noise spectra and audiograms showed that the cyprinids can detect the boats up to several hundred meters distance because the main noise energy is well within the most sensitive hearing range. The hearing generalists, however, probably only perceive the first harmonic of the boat noise at close distances.

Journal Article↗

PubMed2003

How does tripus extirpation affect auditory sensitivity in goldfish?

Otophysine fishes are characterized by Weberian ossicles connecting the swimbladder to the ear acoustically. In order to determine the degree to which these ossicles contribute to auditory sensitivity, the tripus was unilaterally or bilaterally extirpated in goldfish and hearing thresholds determined. The auditory evoked potential (AEP) recording technique was used to measure auditory sensitivity between 100 and 4000 Hz. Bilateral extirpation resulted in a hearing loss at all frequencies ranging from 7 dB at 100 Hz to 33 dB at 2 kHz; no AEPs were detectable at 4 kHz. In contrast to bilateral extirpation, unilateral tripus removal caused no sensitivity change. Pre-exposure to intense white noise caused different threshold shifts in unilaterally versus bilaterally extirpated goldfish. Thresholds increased at all frequencies in unilaterally extirpated goldfish but only at 100 and 200 Hz after bilateral extirpation. The comparison between the hearing generalist Neolamprologus brichardi (family Cichlidae) and the tripus-extirpated otophysine revealed that the latter is still more sensitive than the cichlid. Higher sensitivity in the goldfish after bilateral extirpation as compared to swimbladder elimination indicates that swimbladder oscillations might partly be transmitted to the inner ear independently of the ossicular chain. This suggests that the auditory system in otophysines improves with increasing frequency due to a more efficient connection between the swimbladder and inner ear ensured by the Weberian ossicles.

Air Sacs↗

PubMed2003

Diversity in noise-induced temporary hearing loss in otophysine fishes.

The effects of intense white noise (158 dB re 1 microPa for 12 and 24 h) on the hearing abilities of two otophysine fish species--the nonvocal goldfish Carassius auramus and the vocalizing catfish Pimelodus pictus--were investigated in relation to noise exposure duration. Hearing sensitivity was determined utilizing the auditory brainstem response (ABR) recording technique. Measurements in the frequency range between 0.2 and 4.0 kHz were conducted prior and directly after noise exposure as well as after 3, 7, and 14 days of recovery. Both species showed a significant loss of sensitivity (up to 26 dB in C. auratus and 32 dB in P. pictus) immediately after noise exposure, with the greatest hearing loss in the range of their most sensitive frequencies. Hearing loss differed between both species, and was more pronounced in the catfish. Exposure duration had no influence on hearing loss. Hearing thresholds of C. auratus recovered within three days, whereas those of P. pictus only returned to their initial values within 14 days after exposure in all but one frequency. The results indicate that hearing specialists are affected differently by noise exposure and that acoustic communication might be restricted in noisy habitats.

Acoustic Stimulation↗

PubMed2003

The representation of conspecific sounds in the auditory brainstem of teleost fishes.

Temporal patterns of sounds are thought to be the most important carriers of acoustic information in teleost fishes. In order to investigate how conspecific sounds are processed by the auditory system, auditory brainstem responses (ABRs) elicited by conspecific sounds were recorded in five species of teleosts. In the catfishes Platydoras costatus and Pimelodus pictus, the loach Botia modesta and the labyrinth fish Trichopsis vittata, all of which are hearing specialists, each pulse within the sounds elicited a separate brainwave that closely followed the temporal structure. The ABRs of P. costatus and B. modesta also represent amplitude patterns of conspecific sounds. By contrast, ABRs of the sunfish Lepomis gibbosus, a hearing non-specialist, consisted of long series of waves that could not be attributed to specific sound pulses. A more detailed analysis, however, indicated that each stimulus pulse contributed to the compound ABR waveform. Spectral analysis of low-pitched drumming sounds of P. pictus and corresponding ABRs showed peaks in the ABR spectra at the harmonics of the sound. Our results indicate that, besides temporal patterns, amplitude fluctuations and the frequency content of sounds can be represented in the auditory system and help the fish to extract important information for acoustic communication.

Animal Communication↗

PubMed2002

Can fishes resolve temporal characteristics of sounds? New insights using auditory brainstem responses.

Numerous fish species produce broad-band pulsed sounds with a distinct temporal patterning which is thought to be important during intraspecific communication. In order to determine whether fishes are able to utilize temporal characteristics of acoustic signals, time resolution was determined in four species of otophysines and anabantoids by analyzing auditory brainstem responses (ABRs) to double-click stimuli with varying click periods. At click periods of 3.5 ms, two distinct ABRs were clearly detectable in all species. The minimum pulse period resolvable by the auditory system was below 1.5 ms in each species and slightly intensity-dependent. No differences were found between vocal and non-vocal species within each taxon. Comparisons of the time resolution data to the pulse periods of intraspecific sounds in the vocal species showed that the otophysine Platydoras costatus and the anabantoid Trichopsis vittata are likely to process each pulse within a series of intraspecific sounds. However, as non-vocal and vocal species have a similar minimum resolvable click period, the high temporal resolution capacities of the auditory system of fish might not represent special adaptations for intraspecific acoustic communication. Nonetheless, we suggest that temporal characteristics of naturally occurring conspecific and heterospecific sounds provide reliable information for acoustic communication.

Acoustic Stimulation↗