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Species-specific disturbance calls of five commercially-important characiform species are described, the Curimatidae commonly called branquinhas: Potamorhina latior, Potamorhina altamazonica and Psectrogaster amazonica; Prochilodontidae: jaraquí Semaprochilodus insignis and curimatã Prochilodus nigricans. All species have a two-chambered swimbladder and the sonic mechanism, present exclusively in males, utilises hypertrophied red muscles between ribs that adhere to the anterior chamber. The number of muscles is unusually plastic across species and varies from 1 to 4 pairs suggesting considerable evolution in an otherwise conservative system. Advertisement calls are produced in river confluences in the Madeira Basin during the high-water mating season (January-February). Disturbance calls and sampling allowed recognition of underwater advertisement choruses from P. latior, S. insignis and P. nigricans. The advertisement calls of the first two species have largely similar characteristics and they mate in partially overlapping areas in the Guaporé River. However, P. latior sounds have a lower dominant frequency and it prefers to call from river confluences whereas S. insignis shoals occur mostly in the main river channel adjacent to the confluence. These results help identify and differentiate underwater sounds and evaluate breeding areas during the courtship of commercially important characids likely to be affected by two hydroelectric dams.

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The macroscopic morphology of structures involved in sound generation in the Indian Ocean humpback dolphin (Sousa plumbea) were described for the first time using computed tomography imaging and standard gross dissection techniques. The Indian Ocean humpback dolphin may represent a useful comparative model to the bottlenose dolphin (Tursiops sp.) to provide insights into the functional anatomy of the sound production in dolphins, since these coastal dolphins exhibit similar body size and share similarities on acoustic behavior. The general arrangement of sound generating structures, that is, air sacs and muscles, was similar in both the bottlenose dolphin and the Indian Ocean humpback dolphin. The main difference between the two species existed in a small left posterior branch of the melon in the Indian Ocean humpback dolphin, which was not found in the bottlenose dolphin and might reflect an adaptation of directionality for high frequency communication sounds as seen in some other delphinids (e.g., Lagenorhynchus sp., Grampus griseus). Thus, this may be the main reason for the asymmetry of the sound production structures in dolphins. Additionally, the longer rostrum in Indian Ocean humpback dolphins might suggest a more directional echolocation beam compared to the Lahille's bottlenose dolphin. Anat Rec, 302:849-860, 2019. © 2018 Wiley Periodicals, Inc.

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The effective medium method is used to investigate resonance scattering from schools of fish with gas-filled swim bladders, as a function of frequency and azimuth. Calculations are also performed with a coupled differential equation model, which incorporates both multiple scattering between fish and wave interference interactions of their scattered fields [Feuillade, Nero, and Love, J. Acoust. Soc. Am. 99, 196-208 (1996)]. A theoretical comparison of the models for idealized spherical schools shows good agreement over the entire resonance region in the forward direction, where interference interactions have a minimal effect. Good agreement is also seen in back scattering at low frequencies, where the wavelength λ≥4s, and s is the average nearest neighbor fish separation. If λ<4s, the models diverge in back scattering, and the effective medium method fails. This can be critically important when migrations of schools to deeper water cause the collective resonance frequency to increase. Multiple scattering interactions are negligible when |4πnf(b)(2)/k|⪅0.01, where n is the fish number density, f(b) is the individual fish scattering amplitude, and k=2π/λ. A comparison with forward scattering data shows very good agreement for both models, and indicates a method for estimating fish abundance. For back scattering data, the effective medium method diverges strongly when λ<4s.

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A model used previously to study collective back scattering from fish schools [Feuillade et al., J. Acoust. Soc. Am. 99(1), 196-208 (1996)], is used to analyze the forward scattering properties of these objects. There is an essential physical difference between back and forward scattering from fish schools. Strong frequency dependent interference effects, which affect the back scattered field amplitude, are absent in the forward scattering case. This is critically important for data analysis. There is interest in using back scattering and transmission data from fish schools to study their size, the species and abundance of fish, and fish behavior. Transmission data can be processed to determine the extinction of the field by a school. The extinction of sound depends on the forward scattering characteristics of the school, and data inversion to provide information about the fish should be based upon a forward scattering paradigm. Results are presented of an analysis of transmission data obtained in September 1995 during an experiment performed in the Gulf of Lion in the Mediterranean Sea [Diachok, J. Acoust. Soc. Am. 105(4), 2107-2128 (1999)]. The analysis shows that using forward scattering leads to significantly larger estimates of fish abundance than previous analysis based upon back scattering approaches.

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BACKGROUND: The fish family Sciaenidae has numerous species that produce sounds with superfast muscles that vibrate the swimbladder. These muscles form post embryonically and undergo seasonal hypertrophy-atrophy cycles. The family has been the focus of numerous passive acoustic studies to localize spatial and temporal occurrence of spawning aggregations. Fishes produce disturbance calls when hand-held, and males form aggregations in late afternoon and produce advertisement calls to attract females for mating. Previous studies on five continents have been confined to temperate species. Here we examine the calls of the silver croaker Plagioscion squamosissimus, a freshwater equatorial species, which experiences constant photoperiod, minimal temperature variation but seasonal changes in water depth and color, pH and conductivity. METHODS AND PRINCIPAL FINDINGS: Dissections indicate that sonic muscles are present exclusively in males and that muscles are thicker and redder during the mating season. Disturbance calls were recorded in hand-held fish during the low-water mating season and high-water period outside of the mating season. Advertisement calls were recorded from wild fish that formed aggregations in both periods but only during the mating season from fish in large cages. Disturbance calls consist of a series of short individual pulses in mature males. Advertisement calls start with single and paired pulses followed by greater amplitude multi-pulse bursts with higher peak frequencies than in disturbance calls. Advertisement-like calls also occur in aggregations during the off season, but bursts are shorter with fewer pulses. CONCLUSIONS AND SIGNIFICANCE: Silver croaker produce complex advertisement calls that vary in amplitude, number of cycles per burst and burst duration of their calls. Unlike temperate sciaenids, which only call during the spawning season, silver croaker produce advertisement calls in both seasons. Sonic muscles are thinner, and bursts are shorter than at the spawning peak, but males still produce complex calls outside of the mating season.

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Frequency modulation is a salient acoustic feature of birdsong. Its control is usually attributed to the activity of syringeal muscles, which affect the tension of the labia responsible for sound production. We use experimental and theoretical tools to test the hypothesis that for birds producing tonal sounds such as domestic canaries (Serinus canaria), frequency modulation is determined by both the syringeal tension and the air sac pressure. For different models, we describe the structure of the isofrequency curves, which are sets of parameters leading to sounds presenting the same fundamental frequencies. We show how their shapes determine the relative roles of syringeal tension and air sac pressure in frequency modulation. Finally, we report experiments that allow us to unveil the features of the isofrequency curves.

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The gills and the respiratory swim bladders of juvenile specimens (mean body mass 100g) of the basal teleost Arapaima gigas (Cuvier 1829) were evaluated using stereological methods in vertical sections. The surface areas, harmonic mean barrier thicknesses and morphometric diffusing capacities for oxygen and carbon dioxide were estimated. The average respiratory surface area of the swim bladder (2173 cm² kg⁻¹) exceeded that of the gills (780 cm² kg⁻¹) by a factor of 2.79. Due to the extremely thin air-blood barrier in the swim bladder (harmonic mean 0.22 µm) and the much thicker water-blood barrier of the gills (9.61 µm), the morphometric diffusing capacity for oxygen and carbon dioxide was 88 times greater in the swim bladder than in the gills. These data clearly indicate the importance of the swim bladder, even in juvenile A. gigas that still engage in aquatic respiration. Because of the much greater diffusion constant of CO2 than O2 in water, the gills also remain important for CO2 release.

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The extended boundary condition technique of Waterman [J. Acoust. Soc. Am. 45, 1417-1429 (1969)] has been used to make accurate studies of the frequency and azimuthal scattering distributions from extended axisymmetric acoustic objects. These objects are formed using the mathematical function for a "superellipse" [i.e., (x/a)(s) + z/b)(s) = 1, where s = 2n, n = 1,2,[ellipsis (horizontal)]], and revolving around the z-axis. For s = 2, the object is a spheroid with aspect ratio α = b/a. As s increases, the shape of the object approaches a right circular cylinder of diameter 2a and length 2b. The method is applied to the case of prolate (i.e., α > 1) air-filled objects in water, which has importance for the interpretation of acoustic scattering from oceanic objects such as air-bubbles, the swim bladders of some fish, and zooplankton. It is found that the resonance frequency increases with α, essentially as predicted using a different method by Weston, and increases in a relatively minor way with s. The resonance peak amplitude, and Q, are also more sensitive to changes in α, than s. The method shows that the monopole resonance continues to dominate low frequency scattering, leading to an almost spherically symmetric azimuthal scattering distribution, even for elongated, cylindrical, air-filled, objects with an aspect ratio up to α = 20, and s = 32.

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In songbirds, the ontogeny of singing behavior shows strong parallels with human speech learning. As in humans, development of learned vocal behavior requires exposure to an acoustic model of species-typical vocalizations, and, subsequently, a sensorimotor practice period after which the vocalization is produced in a stereotyped manner. This requires mastering motor instructions driving the vocal organ and the respiratory system. Recently, it was shown that, in the case of canaries (Serinus canaria), the diverse syllables, constituting the song, are generated with air sac pressure patterns with characteristic shapes, remarkably, those belonging to a very specific mathematical family. Here, we treated juvenile canaries with testosterone at the onset of the sensorimotor practice period. This hormone exposure accelerated the development of song into stereotyped adultlike song. After 20 days of testosterone treatment, subsyringeal air sac pressure patterns of song resembled those produced by adults, while those of untreated control birds of the same age did not. Detailed temporal structure and modulation patterns emerged rapidly with testosterone treatment, and all previously identified categories of adult song were observed. This research shows that the known effect of testosterone on the neural circuits gives rise to the stereotyped categories of respiratory motor gestures. Extensive practice of these motor patterns during the sensorimotor phase is not required for their expression.

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Fish damage in hydroelectric stations has been extensively reported, but further investigations focusing on Brazilian migratory species, especially large fish, are needed. The present study describes swimbladder abnormalities in piapara Leporinus obtusidens, a migratory physoclistous species, collected downstream from the Funil Hydroelectric station dam, Minas Gerais, Brazil. The 117 specimens collected were dissected for swimbladder evaluation in the coelomic cavity. The abnormalities detected in 14 of the fish (12 percent) were swimbladder rupture with exteriorization (N = 12) and formation of sac-like projections (N = 2). The specimens that had swimbladder abnormalities weighed over 1300 g for both sexes. These abnormalities may be caused by bladder infections, however, inflammation process were not detected in these fish. The presence of anomalies in swimbladder suggests that the individuals were subjected to sudden depressurization, possibly related to passage through the turbines. Further comparative studies are needed to corroborate this hypothesis.(AU)

Os danos que as usinas hidrelétricas causam na fauna aquática tem sido relatados, mas novos estudos focando as espécies nativas, especialmente os peixes de grande porte são necessários. O presente estudo descreve as anomalias de bexiga natatória em piapara Leporinus obtusidens, uma espécie de peixe migratório, coletados a jusante da barragem da estação Hidrelétrica do Funil, Minas Gerais, Brasil. Os 117 exemplares coletados foram dissecados para avaliação da bexiga natatória na cavidade celomática. As anormalidades detectadas em 14 dos peixes capturados (12 por cento) foram ruptura do tecido com exteriorização da bexiga natatória (N = 12) e formação de projeções da bexiga (N = 2). Os exemplares que apresentavam anormalidades de bexiga, possuíam peso superior a 1300 g em ambos os sexos. Este tipo de anomalia pode ser causado por processo infeccioso da bexiga, no entanto, não foram detectados processos inflamatórios nesses peixes. O quadro de anomalias em bexiga natatória em piapara sugere que os indivíduos foram submetidos a uma brusca despressurização, possivelmente relacionada à passagem pelas turbinas. Outros estudos comparativos são necessários para corroborar esta hipótese.(AU)

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Fish damage in hydroelectric stations has been extensively reported, but further investigations focusing on Brazilian migratory species, especially large fish, are needed. The present study describes swimbladder abnormalities in piapara Leporinus obtusidens, a migratory physoclistous species, collected downstream from the Funil Hydroelectric station dam, Minas Gerais, Brazil. The 117 specimens collected were dissected for swimbladder evaluation in the coelomic cavity. The abnormalities detected in 14 of the fish (12 percent) were swimbladder rupture with exteriorization (N = 12) and formation of sac-like projections (N = 2). The specimens that had swimbladder abnormalities weighed over 1300 g for both sexes. These abnormalities may be caused by bladder infections, however, inflammation process were not detected in these fish. The presence of anomalies in swimbladder suggests that the individuals were subjected to sudden depressurization, possibly related to passage through the turbines. Further comparative studies are needed to corroborate this hypothesis.

Os danos que as usinas hidrelétricas causam na fauna aquática tem sido relatados, mas novos estudos focando as espécies nativas, especialmente os peixes de grande porte são necessários. O presente estudo descreve as anomalias de bexiga natatória em piapara Leporinus obtusidens, uma espécie de peixe migratório, coletados a jusante da barragem da estação Hidrelétrica do Funil, Minas Gerais, Brasil. Os 117 exemplares coletados foram dissecados para avaliação da bexiga natatória na cavidade celomática. As anormalidades detectadas em 14 dos peixes capturados (12 por cento) foram ruptura do tecido com exteriorização da bexiga natatória (N = 12) e formação de projeções da bexiga (N = 2). Os exemplares que apresentavam anormalidades de bexiga, possuíam peso superior a 1300 g em ambos os sexos. Este tipo de anomalia pode ser causado por processo infeccioso da bexiga, no entanto, não foram detectados processos inflamatórios nesses peixes. O quadro de anomalias em bexiga natatória em piapara sugere que os indivíduos foram submetidos a uma brusca despressurização, possivelmente relacionada à passagem pelas turbinas. Outros estudos comparativos são necessários para corroborar esta hipótese.

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During song production, oscine birds produce large air sac pressure pulses. During those pulses, energy is transferred to labia located at the juncture between the bronchii and the trachea, inducing the high frequency labial oscillations which are responsible for airflow modulations, i.e., the uttered sound. In order to generate diverse syllables, canaries (Serinus canaria) use a set of air sac pressure patterns with characteristic shapes. In this work we show that these different shapes can be approximated by the subharmonic solutions of a forced normal form. This simple model is built from identifying dynamical elements which allow to reproduce the shape of the pressure pattern corresponding to one syllable type. Remarkably, integrating that simple model for other parameters allows to recover the other pressure patterns used during song. Interpreting the diversity of these physiological gestures as subharmonic solutions of a simple nonlinear system allows us to account simultaneously for their morphological features as well as for the syllabic timing and suggests a strategy for the generation of complex motor patterns.

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BACKGROUND: Living birds possess a unique heterogeneous pulmonary system composed of a rigid, dorsally-anchored lung and several compliant air sacs that operate as bellows, driving inspired air through the lung. Evidence from the fossil record for the origin and evolution of this system is extremely limited, because lungs do not fossilize and because the bellow-like air sacs in living birds only rarely penetrate (pneumatize) skeletal bone and thus leave a record of their presence. METHODOLOGY/PRINCIPAL FINDINGS: We describe a new predatory dinosaur from Upper Cretaceous rocks in Argentina, Aerosteon riocoloradensis gen. et sp. nov., that exhibits extreme pneumatization of skeletal bone, including pneumatic hollowing of the furcula and ilium. In living birds, these two bones are pneumatized by diverticulae of air sacs (clavicular, abdominal) that are involved in pulmonary ventilation. We also describe several pneumatized gastralia ("stomach ribs"), which suggest that diverticulae of the air sac system were present in surface tissues of the thorax. CONCLUSIONS/SIGNIFICANCE: We present a four-phase model for the evolution of avian air sacs and costosternal-driven lung ventilation based on the known fossil record of theropod dinosaurs and osteological correlates in extant birds: (1) Phase I-Elaboration of paraxial cervical air sacs in basal theropods no later than the earliest Late Triassic. (2) Phase II-Differentiation of avian ventilatory air sacs, including both cranial (clavicular air sac) and caudal (abdominal air sac) divisions, in basal tetanurans during the Jurassic. A heterogeneous respiratory tract with compliant air sacs, in turn, suggests the presence of rigid, dorsally attached lungs with flow-through ventilation. (3) Phase III-Evolution of a primitive costosternal pump in maniraptoriform theropods before the close of the Jurassic. (4) Phase IV-Evolution of an advanced costosternal pump in maniraptoran theropods before the close of the Jurassic. In addition, we conclude: (5) The advent of avian unidirectional lung ventilation is not possible to pinpoint, as osteological correlates have yet to be identified for uni- or bidirectional lung ventilation. (6) The origin and evolution of avian air sacs may have been driven by one or more of the following three factors: flow-through lung ventilation, locomotory balance, and/or thermal regulation.

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In this work we study the generation of respiratory patterns by oscine birds. We present a model capable of generating realistic respiratory patterns, during normal respiration and song production. The model accounts for the interaction between neural nuclei and air sac dynamics. We performed experiments in vivo in order to test the predictions of the model, measuring air sac pressure during song and normal respiration in canaries (Serinus canaria).

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Ducks become slightly hyperthermic at ambient temperatures (TA) above 35 degrees C, as indicated by cloacal temperature measurements. The air sacs do not represent important sites of evaporation, since their wall and air temperatures are not lower than ambient and body (cloacal) temperatures during thermal panting. Upon exposure to moderate heat loads (TA = 35 degrees C), arterial PO2 and PCO2 are relatively constant, whereas pH increases slightly. During exposure to heavy heat loads (TA = 42 degrees C), however, ducks become alkalotic, as indicated by a significant increase in arterial pH.

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