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A N Popper

Publications and source records attributed to A N Popper.

72 records · Page 4Linked to original sources
PubMed1981

Comparative scanning electron microscopic investigations of the sensory epithelia in the teleost sacculus and lagena.

Scanning electron microscopic studies were conducted on the sensory epithelia of the auditory portions of the ears in teleost species representing wide taxonomic diversity. A number of the features of the ears investigated resembled features found in other teleost species, although some major exceptions to earlier patterns were found, particularly in the saccular sensory epithelium. The saccular maculae of all but one species contained basically similar ciliary bundles on the sensory hair cells while there was some significant variation on the lagenar maculae. Hair cell orientation patterns on the sacculus contained four orientation groups in all of the species, other than the mormyrid, Gnathonemus, which only had two groups. Lagenar maculae had two orientation groups, and the orientation patterns were similar to one another. The most divergent form of lagenar macula was found in gnathonemus. These data, combined with data from earlier investigations, provide a broad overview of the surface features of the ear in teleost fishes. Most significantly, it now appears that there are at least five different saccular hair cell orientation patterns among teleost fishes, and all of these patterns are found spread through many major teleost taxa. While there is some similarity in ear structures among some groups of closely related species, such as the Elopomorpha and the Gadiformes, it is becoming more apparent that there is extensive convergence in a number of features of he teleost ear that most likely reflect similar selective pressures during the evolution of the ear. The nature of these selective pressures, however, are not well understood.

Acoustic Maculae↗
PubMed1981

The fine structure of the sacculus and lagena of a teleost fish.

The ultrastructure of the sensory epithelia in the auditory regions of the ear, the sacculus and lagena, were investigated in the blue gourami, Trichogaster trichopterus, using transmission and scanning electron microscopy. The sensory epithelium consists of sensory hair cells surrounded by supporting cells, both of which are quite similar to comparable cells found in other fishes. The apical surface of each sensory cell contains a ciliary bundle which varies in length in different epithelial regions. Tight junctions and one or more levels of desmosomes are located between supporting cells, and between sensory and supporting cells, just below the apical cell membrane. Peripheral to the actual sensory epithelium is a region of epithelial cells that resemble the supporting cells on the sensory epithelium itself. However, interspersed among these cells are other cells containing large numbers of mitochondria, extensive smooth endoplasmic reticulum, and large vacuoles. Investigations of the orientation patterns of the ciliary bundles on the sensory hair cells demonstrate that the lagena is typical of other Perciform fishes while the position of two of the four orientation groups normally found in the Perciform sacculus are quite different in Trichogaster from that found in other species. Comparisons of the ultrastructure of the sensory and supporting epithelia of Trichogaster and other fishes shows that, with the exception of the mitochondria-filled cells, there are no apparent significant interspecific differences with regard to ultrastructure of the sensory and supporting cells themselves, although there are differences in hair cell orientation patterns among the same fish groups.

Animals↗
PubMed1979

Non-simultaneous auditory masking in the goldfish, Carassius auratus.

Auditory thresholds were determined for 500 HZ pure tone pulses of 15, 25 and 50 ms duration presented leading, following or simultaneously with noise pulses of 50 or 250 ms duration. Masking by the noise decreased: (i) with an increase in tone pulse duration; (ii) with a shortening of the noise pulse duration; and (iii) as the interval between tone and noise pulses was increased from 0 to 350 ms. The effect of the noise was independent of whether the noise led or followed the pure tone. It is suggested that the most significant factor affecting masking was the duration of the interval between tone and noise, and that the site for the interactions between signals is central to the inner ear.

Animals↗
PubMed1978

Scanning electron microscopic study of the otolithic organs in the bichir (Polypterus bichir) and shovel-nose sturgeon (Scaphirhynchus platorynchus).

The anatomy and ultrastructure of the sacculus, lagena, and utriculus of the ear of Polypterus bichir and Scaphirhynchus platorynchus were studied using the scanning electron microscope. The otolithic organs each contain a single dense calcareous otolith in close contact with a sensory epithelium (macula). The maculae have sensory hair cells typical of those found in other vertebrates, surrounded by microvilli-covered supporting cells. The hair cells on each macula are divided into several groups, with all of the cells in each group morphologically polarized in the same direction. The cells of the utricular macula in both species are divided into opposing groups in a pattern similar to that found in other vertebrates. The saccular and lagenar maculae are located in a single large chamber in both species. In Scaphirhychus the two maculae are on the same plane, while in Polypterus they are at right angles to one another. The hair cells on the saccular maculae of both species are divided into two oppositely oriented groups. In Scaphirhynchus the cells on the posterior half of the macula are oriented dorsally on the dorsal half of the macula and ventrally on the ventral half. The anterior region of the macula is rotated and the cells of the dorsal and ventral groups are shifted so that they are oriented on the animal's horizon plane. A similar pattern is found in Polypterus, except that this macula is shaped like a "J" with the vertical portion of the J having horizontal cells and the bottom portion vertical cells. The lagenar maculae in both species have dorsally oriented cells on the anterior side of the macula and ventrally oriented cells on the posterior half of the macula. While these data are not sufficient for clarifying the taxonomic relationship between the two species studied, it is clear that the ears in these species have a number of significant differences from the teleost ear that could have functional and/or taxonomic significance.

Animals↗
PubMed1976

Ultrastructure of the auditory regions in the inner ear of the lake whitefish.

Hair cell polarization patterns were investigated on the sensory macule of the sacculus and lagena of the lake whitefish. The saccular hair cells are divided into four groups, with all of the cells within a group having the same orientation. Saccular orientations are anterior, posterior, dorsal, and ventral with respect to the axis of the animal. Two groups, one dorsal and one ventral, are found on the lagena. The saccular orientations are significantly different from those in tetrapods. Since this organ appears to have different functions in fish and tetrapods it is likely that the orientation patterns in fish are adapted to some aspect of audition--perhaps directional localization of sound.

Animals↗
PubMed1975

Laser light-scattering investigations of the teleost swimbladder response to acoustic stimuli.

When a laser pencil is directed through the teleost swimbladder fringe patterns can be seen in the far-field that are (a) highly sensitive to the orientation and position of the swimbladder with respect to the incident pencil and (b) a representation of contributions from each membrane through which the light passes. The fringe pattern fluctuates in intensity, and to some extent in position, in response to driving forces that distort the swimbladder. The spectrum of these very small distortions can be measured by standard light scattering techniques. This method was used to study the response of in situ swimbladders to imposed acoustic fields and evidence for a sharp roll-off of the response at frequencies above 1,000 Hz was found. Models for these effects are discussed.

Acoustic Stimulation↗
PubMed1975

Modes of stimulation of the teleost ear.

Microphonic potentials were recorded from the inner ears of a catfish (Ictalurus punctatus) and an African mouthbreeder (Tilapia macrocephala) in response to underwater sound stimulation and direct vibration of the head. The shape of the vibratory isopotential functions of frequency was similar in both species up to 600 HZ. Above 600 HZ, the sensitivity of Ictalurus continued to increase to 4000 HZ while the sensitivity of Tilapia declined. Deflation of the swim bladder did not affect the response to vibration in either species, the response of Tilapia to the underwater sound stimulus being minimal and unaffected by removal of the swim bladder. Ictalurus was pressure-sensitive to above 4000 HZ, ther being a significant dedline in the response with deflation of the swimbladder.

Acoustic Stimulation↗
PubMed1975

Sound localization by the bottlenose porpoise Tursiops truncatus.

1. Sound localization was measured behaviourally for the Atlantic bottlenose porpoise (Tursiops truncatus) using a wide range of pure tone pulses as well as clicks simulating the species echolocation click. 2. Measurements of the minimum audible angle (MAA) on the horizontal plane give localization discrimination thresholds of between 2 and 3 degrees for sounds from 20 to 90 kHz and thresholds from 2-8 to 4 degrees at 6, 10 and 100 kHz. With the azimuth of the animal changed relative to the speakers the MAAs were 1-3-1-5 degrees at an azimuth of 15 degrees and about 5 degrees for an azimuth of 30 degrees. 3. MAAs to clicks were 0-7-0-8 degrees. 4. The animal was able to do almost as well in determining the position of vertical sound sources as it could for horizontal localization. 5. The data indicate that at low frequencies the animal may have been localizing by using the region around the external auditory meatus as a detector, but at frequencies about 20 kHz it is likely that the animal was detecting sounds through the lateral sides of the lower jaw. 6. Above 20 kHz, it is likely that the animal was localizing using binaural intensity cues. 7. Our data support evidence that the lower jaw is an important channel for sound detection in Tursiops.

Animals↗