[Characterization of beam patterns of bottlenose dolphin in the transversal plane].

The characteristics of the absolute auditory sensitivity of the bottlenose dolphin (Tursiops truncatus p.) in the transverse plane have been measured using short broad-band stimuli simulating dolphin clicks (with energy maximum at frequencies 8, 16, 30, 50 and 100 kHz). Experiments were performed using the method of conditioned reflexes with food reinforcement. It was shown that, in the frequency range of 8-30 kHz, the absolute sensitivity of dolphin hearing in any ventral and lateral directions of the transverse plane is only by 2-8 dB worse than in the nasal direction. Moreover, it is approximately by 25-30 dB better than at frequencies of 50-100 kHz. At frequencies of 8-30 kHz, a pronounced dorsoventral asymmetry has been observed. In this frequency range, it reaches approximately 15-18 dB whereas at frequencies of 50-100 kHz, this asymmetry decreases to 2-3 dB. In the dorsal direction, the auditory sensitivity is by 18 dB worse than in the nasal one at frequencies of around 8 kHz, and the difference rises smoothly to 33 dB at frequencies of about 100 kHz. At frequencies of 50-100 kHz, the acoustical thresholds of the cross-section plane in comparison with thresholds for the with nasal direction get worse almost uniformly in all directions by 25-33 dB. As a result, in the transversal plane, the beam patterns have a nearly circular form, unlike the patterns at frequencies of 8-30 kHz. The results are discussed in terms of the model of sound perception through the left and right mental foramens. The biological expediency of the asymmetry is emphasized.

[The conduction of tonal and compound sounds through the body of a bottlenose dolphin].

The peculiarities of underwater sound conduction through the body of the Black Sea bottlenose dolphin (Tursiops truncatus p.) were investigated to elucidate the mechanisms of acoustic orientation of marine mammals. By using the method of instrumental conditioned reflexes with food reinforcement, underwater hearing thresholds in the bottlenose dolphin depending on signal parameters (tonal pulses and various noises) and sound conduction pathways were measured under conditions of full and partial (with the head out of water and sound being conducted through the body tissues) submergence of the animal into water. The underwater hearing thresholds increased by 6-27 dB upon sound conduction through the body tissues (to the least extent for tonal pulses of 10 and 20 kHz). The hearing thresholds for tonal pulses and narrow-band noises were very similar both under conditions of full and partial submergence of the animal into water.

[The localization of the sound source in the vertical plane by a bottlenose dolphin].

The accuracy of localizing the underwater sound source in the vertical-plane by the bottlenose dolphin was investigated using the method of instrumental conditioned reflexes with food reinforcement. The accuracy of determining the underwater sound in the vertical plane (the full angle) was on the average: 2 - 2,5 degrees for tonal signals with frequencies of 5, 20, and 120 kHz; pulsed clicks with the central frequency of 120 kHz and the exponential forms of amplitude alteration wavefronts were localized by the dolphin with an accuracy of 1,5 degrees. Among all marine mammals examined, dolphins are characterized by the maximal exact analysis of acoustic space.

[The underwater and airborne horizontal localization of sound by the northern fur seal]. / Lokalizatsiia istochnika zvuka severnym morskim kotikom v gorizontal'noi ploskosti v vodnoi i vozdushnoi sredakh.

The accuracy of the underwater and airborne horizontal localization of different acoustic signals by the northern fur seal was investigated by the method of instrumental conditioned reflexes with food reinforcement. For pure-tone pulsed signals in the frequency range of 0.5-25 kHz the minimum angles of sound localization at 75% of correct responses corresponded to sound transducer azimuth of 6.5-7.5 degrees +/- 0.1-0.4 degrees underwater (at impulse duration of 3-90 ms) and of 3.5-5.5 degrees +/- 0.05-0.5 degrees in air (at impulse duration of 3-160 ms). The source of pulsed noise signals (of 3-ms duration) was localized with the accuracy of 3.0 degrees +/- 0.2 degrees underwater. The source of continuous (of 1-s duration) narrow band (10% of c.fr.) noise signals was localized in air with the accuracy of 2-5 degrees +/- 0.02-0.4 degrees and of continuous broad band (1-20 kHz) noise, with the accuracy of 4.5 degrees +/- 0.2 degrees.

[Frequency discrimination by the bottle-nosed dolphin and the Northern fur seal depending on sound parameters and sound conduction pathways]. / Chastotnoe razlichenie v slukhe del'fina afaliny i severnogo morskogo kotika v zavisimosti ot parametrov i putei provedeniia zvuka.

Underwater differential frequency hearing thresholds in the Black Sea bottle-nosed dolphin (Tursiops truncatus p.) and the northern fur seal (Callorhinus ursinus) were measured depending on signal frequency and sound conduction pathways. The measurements were performed by the method of instrumental conditioned reflexes with food reinforcement under conditions of full and partial (with heads out of water at sound conduction through body tissues) submergence of animals into water. It was shown that in a frequency range of 5-100 kHz, underwater differential frequency hearing thresholds of the bottle-nosed dolphin changed from 0.46-0.60% to 0.21-0.34% and depended little on sound conduction pathways. The minimum underwater differential frequency hearing thresholds of the northern fur seal corresponded to the frequencies of maximum hearing sensitivity, changed from 1.7% to 1-2.3% in a frequency range of 1-20 kHz, sharply increased at the edges of the frequency hearing perception range, and depended little (in a range of 5-40 kHz) on sound conduction pathways. Thus, underwater sounds propagating through the body tissues of dolphin and fur seal reach the inner ear.

[Localization of a sum of acoustic signals in air by the northern fur seal]. / Lokalizatsiia summy akusticheskikh signalov severnym morskim kotikom v vozdushnoi srede.

The localization of a sum of acoustic signals by two northern fur seals in air depending on sound parameters was investigated using the method of instrumental conditioned reflexes with food reinforcement. It was found that sound perception of northern fur seal proceeds by the binaural mechanism. The time/intensity interchange coefficient was 570 microseconds/dB for series of clicks (with amplitude maximum at 1 kHz) and 250 microseconds/dB for tonal impulses with a frequency of 1 kHz. With click amplitudes being equal, the number of approaches of the animal to the source of the first signal reached a 75% level at a delay of the second signal 0.07 ms (the minimum delay); with a delay of 6 ms (the maximum delay) and more, the fur seal, probably hears two separate signals. The minimum delay depended little on the duration of tonal impulses (with a frequency of 1 kHz) and was 0.3-0.7 ms; the maximum delay was 9-11 ms for tonal impulses with a duration of 3 ms and 37-40 ms with impulse duration 20 ms. The precedence effect became apparent at a greater delay for smooth fronts of impulses than for rectangular fronts.

[Combined gastrectomies with formation of an artificial stomach by a new method]. / O kombinirovannykh gastrektomiiakh s formirovaniem iskusstvennogo zheludka po novoi metodike.

A new method for jejunoplasty was used in 29 combined gastrectomies. Postoperative lethality was 17.2%.