The effects of anthropogenic sources of sound on fishes.

There is increasing concern about the effects of pile driving and other anthropogenic (human-generated) sound on fishes. Although there is a growing body of reports examining this issue, little of the work is found in the peer-reviewed literature. This review critically examines both the peer-reviewed and 'grey' literature, with the goal of determining what is known and not known about effects on fish. A companion piece provides an analysis of the available data and applies it to estimate noise exposure criteria for pile driving and other impulsive sounds. The critical literature review concludes that very little is known about effects of pile driving and other anthropogenic sounds on fishes, and that it is not yet possible to extrapolate from one experiment to other signal parameters of the same sound, to other types of sounds, to other effects, or to other species.

Patients with IgA nephropathy have increased serum galactose-deficient IgA1 levels.

Immunoglobulin A (IgA) nephropathy is the most prevalent form of glomerulonephritis worldwide. A renal biopsy is required for an accurate diagnosis, as no convenient biomarker is currently available. We developed a serological test based upon the observation that this nephropathy is characterized by undergalactosylated IgA1 in the circulation and in mesangial immune deposits. In the absence of galactose, the terminal saccharide of O-linked chains in the hinge region of IgA1 is terminal or sialylated N-acetylgalactosamine. A lectin from Helix aspersa, recognizing N-acetylgalactosamine, was used to develop an enzyme-linked immunosorbent assay that measures galactose-deficient IgA1 in serum. The median serum lectin-binding IgA1 level was significantly higher for 153 Caucasian adult patients with IgA nephropathy without progression to end-stage renal disease as compared with that for 150 healthy Caucasian adult controls. As the lectin-binding IgA1 levels for the controls were not normally distributed, the 90th percentile was used for determination of significant elevation. Using a value of 1076 U/ml as the upper limit of normal, 117 of the 153 patients with IgA nephropathy had an elevated serum lectin-binding IgA1 level. The sensitivity as a diagnostic test was 76.5%, with specificity 94%; the positive predictive value was 88.6% and the negative predictive value was 78.9%. We conclude that this lectin-binding assay may have potential as a noninvasive diagnostic test for IgA nephropathy.

Development of ultrasound detection in American shad (Alosa sapidissima).

It has recently been shown that a few fish species, including American shad (Alosa sapidissima; Clupeiformes), are able to detect sound up to 180 kHz, an ability not found in most other fishes. Initially, it was proposed that ultrasound detection in shad involves the auditory bullae, swim bladder extensions found in all members of the Clupeiformes. However, while all clupeiformes have bullae, not all can detect ultrasound. Thus, the bullae alone are not sufficient to explain ultrasound detection. In this study, we used a developmental approach to determine when ultrasound detection begins and how the ability to detect ultrasound changes with ontogeny in American shad. We then compared changes in auditory function with morphological development to identify structures that are potentially responsible for ultrasound detection. We found that the auditory bullae and all three auditory end organs are present well before fish show ultrasound detection behaviourally and we suggest that an additional specialization in the utricle (one of the auditory end organs) forms coincident with the onset of ultrasound detection. We further show that this utricular specialization is found in two clupeiform species that can detect ultrasound but not in two clupeiform species not capable of ultrasound detection. Thus, it appears that ultrasound-detecting clupeiformes have undergone structural modification of the utricle that allows detection of ultrasonic stimulation.

A mathematical analysis of the peripheral auditory system mechanics in the goldfish (Carassius auratus).

The dynamic response of the goldfish peripheral auditory system has been analyzed using lumped-parameter mechanical and fluid system models for the swimbladder, Weberian apparatus, and saccule. The swimbladder is treated as a two degree-of-freedom mechanical system consisting of two coupled mass-spring-damper arrangements. The swimbladder is coupled to the Weberian ossicles using a phenomenological analysis of the anterior swimbladder tunica externa which permits both stretching and sliding. Analysis of the saccule features only a single degree of freedom, corresponding to the direction of orientation of the ciliary bundles. Inputs to the saccule consist of the transverse canal fluid motion and the motion of the animal's head (assumed to match the local acoustic particle motion). Mechanical properties required for the system equations were estimated from published literature, direct measurements, and curve fits to experimental data for the motions of the swimbladders. The results indicate that the Weberian apparatus has a significant impact on hearing ability over the entire auditory bandwidth, not just at higher frequencies, and that the saccule functions as a displacement sensor above approximately 300 Hz.

Detection of ultrasonic tones and simulated dolphin echolocation clicks by a teleost fish, the American shad (Alosa sapidissima).

The authors previously reported that American shad (Alosa sapidissima) can detect sounds from 100 Hz to 180 kHz, with two regions of best sensitivity, one from 200 to 800 Hz and the other from 25 to 150 kHz [Mann et al., Nature 389, 341 (1997)]. These results demonstrated ultrasonic hearing by shad, but thresholds at lower frequencies were potentially masked by background noise in the experimental room. In this study, the thresholds of the American shad in a quieter and smaller tank, as well as thresholds for detecting stimulated echolocation sounds of bottlenosed dolphins was determined. Shad had lower thresholds for detection (from 0.2 to 0.8 kHz) in the quieter and smaller tank compared with the previous experiment, with low-frequency background noise but similar thresholds at ultrasonic frequencies. Shad were also able to detect echolocation clicks with a threshold of 171 dB re: 1 microPa peak to peak. If spherical spreading and an absorption coefficient of 0.02 dB/m of dolphin echolocation clicks are assumed, shad should be able to detect echolocating Tursiops truncatus at ranges up to 187 m. The authors propose that ultrasonic hearing evolved in shad in response to selection pressures from echolocating odontocete cetaceans.

Effects of low-frequency underwater sound on hair cells of the inner ear and lateral line of the teleost fish Astronotus ocellatus.

Fish (Astronotus ocellatus, the oscar) were subject to pure tones in order to determine the effects of sound at levels typical of man-made sources on the sensory epithelia of the ear and the lateral line. Sounds varied in frequency (60 or 300 Hz), duty cycle (20% or continuous), and intensity (100, 140, or 180 dB re: 1 muPa). Fish were allowed to survive for 1 or 4 days posttreatment. Tissue was then evaluated using scanning electron microscopy to assess the presence or absence of ciliary bundles on the sensory hair cells on each of the otic endorgans and the lateral line. The only damage that was observed was in four of five fish stimulated with 300-Hz continuous tones at 180 dB re: 1 muPa and allowed to survive for 4 days. Damage was limited to small regions of the striola of the utricle and lagena. There was no damage in any other endorgan, and the size and location of the damage varied between specimens. No damage was observed in fish that had been allowed to survive for 1 day poststimulation, suggesting that damage may develop slowly after exposure.

Processing of acoustic signals in the auditory system of bony fish.

In order to determine unambiguously the bearing of a sound source, a fish must be able to resolve acoustic pressure and the components of the acoustic displacement vector from the signals detected by the otolithic organs. A new hypothesis for the processing of acoustical information by bony fish is presented. It is demonstrated that much of the processing required to do this may be implicit in the structure of the ear and its associated neural innervation. Possible algorithms are presented that the central nervous system might use to further process the derived information to localize a sound source and discriminate frequency and range. The hypothesis is shown to be consistent with much of what is known of the morphology and physiology of the auditory system of bony fishes.