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Lin FC, Lin SM, Godfrey SS. Hidden social complexity behind vocal and acoustic communication in non-avian reptiles. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230200. [PMID: 38768204 DOI: 10.1098/rstb.2023.0200] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 01/08/2024] [Indexed: 05/22/2024] Open
Abstract
Social interactions are inevitable in the lives of most animals, since most essential behaviours require interaction with conspecifics, such as mating and competing for resources. Non-avian reptiles are typically viewed as solitary animals that predominantly use their vision and olfaction to communicate with conspecifics. Nevertheless, in recent years, evidence is mounting that some reptiles can produce sounds and have the potential for acoustic communication. Reptiles that can produce sound have an additional communicative channel (in addition to visual/olfactory channels), which could suggest they have a higher communicative complexity, the evolution of which is assumed to be driven by the need of social interactions. Thus, acoustic reptiles may provide an opportunity to unveil the true social complexity of reptiles that are usually thought of as solitary. This review aims to reveal the hidden social interactions behind the use of sounds in non-avian reptiles. Our review suggests that the potential of vocal and acoustic communication and the complexity of social interactions may be underestimated in non-avian reptiles, and that acoustic reptiles may provide a great opportunity to uncover the coevolution between sociality and communication in non-avian reptiles. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamics'.
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Affiliation(s)
- Feng-Chun Lin
- Department of Zoology, University of Otago , Dunedin, New Zealand
| | - Si-Min Lin
- School of Life Science, National Taiwan Normal University , Taipei, Taiwan
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2
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Heffner HE, Koay G, Heffner RS. Hearing in helmeted guineafowl (Numida meleagris): audiogram from 2 Hz to 10 kHz and localization acuity for brief noise bursts. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024; 210:65-73. [PMID: 37280367 DOI: 10.1007/s00359-023-01645-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/16/2023] [Accepted: 05/25/2023] [Indexed: 06/08/2023]
Abstract
Behavioral hearing thresholds and noise localization acuity were determined using a conditioned avoidance/suppression procedure for three Helmeted guineafowl (Numida meleagris). The guineafowl responded to frequencies as low as 2 Hz at 82.5 dB SPL, and as high as 8 kHz at 84.5 dB SPL. At a level of 60 dB SPL, their hearing range spanned 8.12 octaves (24.6 Hz-6.86 kHz). Like most birds, they do not hear sounds above 8 kHz. However, the guineafowl demonstrated good low-frequency hearing (frequencies below 32 Hz), showing thresholds that are more sensitive than both the peafowl and pigeon, both of which hear infrasound. It thus appears that infrasound perception may be more common than previously thought and may have implications for species that inhabit areas with wind energy facilities. The guineafowls' minimum audible angle for a 100-ms broadband noise burst was 13.8 °, at the median for birds and near the mean for mammals. Unlike in mammals, the small sample of bird species and limited representation of lifestyles do not yet allow for meaningful interpretations of the selective pressures or mechanisms that underlie their abilities to locate sound sources.
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Affiliation(s)
- Henry E Heffner
- Department of Psychology, University of Toledo, Toledo, OH, USA
| | - Gimseong Koay
- Department of Psychology, University of Toledo, Toledo, OH, USA
| | - Rickye S Heffner
- Department of Psychology, University of Toledo, Toledo, OH, USA.
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3
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Young BA, Cramberg M. The anatomical basis of amphibious hearing in the American alligator (Alligator mississippiensis). Anat Rec (Hoboken) 2024; 307:198-207. [PMID: 37259899 DOI: 10.1002/ar.25272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 04/27/2023] [Accepted: 05/21/2023] [Indexed: 06/02/2023]
Abstract
The different velocities of sound (pressure waves) in air and water make auditory source localization a challenge for amphibious animals. The American alligator (Alligator mississippiensis) has an extracolumellar cartilage that abuts the deep surface of the tympanic membrane, and then expands in size beyond the caudal margin of the tympanum. This extracolumellar expansion is the insertion site for two antagonistic skeletal muscles, the tensor tympani, and the depressor tympani. These muscles function to modulate the tension in the tympanic membrane, presumably as part of the well-developed submergence reflex of Alligator. All crocodilians, including Alligator, have internally coupled ears in which paratympanic sinuses connect the contralateral middle ear cavities. The temporal performance of internally coupled ears is determined, in part, by the tension of the tympanic membrane. Switching between a "tensed" and "relaxed" tympanic membrane may allow Alligator to compensate for the increased velocity of sound underwater and, in this way, use a single auditory map for sound localization in two very different physical environments.
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Affiliation(s)
- Bruce A Young
- Department of Anatomy, Kirksville College of Osteopathic Medicine, Kirksville, Missouri, USA
| | - Michael Cramberg
- Department of Anatomy, Kirksville College of Osteopathic Medicine, Kirksville, Missouri, USA
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4
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Thévenet J, Papet L, Campos Z, Greenfield M, Boyer N, Grimault N, Mathevon N. Spatial release from masking in crocodilians. Commun Biol 2022; 5:869. [PMID: 36008592 PMCID: PMC9411511 DOI: 10.1038/s42003-022-03799-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 08/04/2022] [Indexed: 11/17/2022] Open
Abstract
Ambient noise is a major constraint on acoustic communication in both animals and humans. One mechanism to overcome this problem is Spatial Release from Masking (SRM), the ability to distinguish a target sound signal from masking noise when both sources are spatially separated. SRM is well described in humans but has been poorly explored in animals. Although laboratory tests with trained individuals have suggested that SRM may be a widespread ability in vertebrates, it may play a limited role in natural environments. Here we combine field experiments with investigations in captivity to test whether crocodilians experience SRM. We show that 2 species of crocodilians are able to use SRM in their natural habitat and that it quickly becomes effective for small angles between the target signal source and the noise source, becoming maximal when the angle exceeds 15∘. Crocodiles can therefore take advantage of SRM to improve sound scene analysis and the detection of biologically relevant signals. The ability to separate target sound signals from masking noise is identified in wild and captive crocodilian species.
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Affiliation(s)
- Julie Thévenet
- Equipe de Neuro-Ethologie Sensorielle ENES / CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne, France. .,Equipe Cognition Auditive et Psychoacoustique / CRNL, CNRS, Inserm, University Lyon 1, Bron, France.
| | - Léo Papet
- Equipe de Neuro-Ethologie Sensorielle ENES / CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne, France. .,Equipe Cognition Auditive et Psychoacoustique / CRNL, CNRS, Inserm, University Lyon 1, Bron, France.
| | - Zilca Campos
- Wildlife Laboratory, Brazilian Agricultural Research Corporation EMBRAPA, Corumbá, Brazil
| | - Michael Greenfield
- Equipe de Neuro-Ethologie Sensorielle ENES / CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne, France.,Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, 66045, USA
| | - Nicolas Boyer
- Equipe de Neuro-Ethologie Sensorielle ENES / CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne, France
| | - Nicolas Grimault
- Equipe Cognition Auditive et Psychoacoustique / CRNL, CNRS, Inserm, University Lyon 1, Bron, France
| | - Nicolas Mathevon
- Equipe de Neuro-Ethologie Sensorielle ENES / CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne, France
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Wang T, Li H, Chen B, Cui J, Shi H, Wang J. Effect of Temperature on the Plasticity of Peripheral Hearing Sensitivity to Airborne Sound in the Male Red-Eared Slider Trachemys scripta elegans. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.856660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Chelonians are considered the least vocally active group of extant reptiles and known as “low-frequency specialists” with a hearing range of <1.0 kHz. As they are ectothermic organisms, most of their physiological and metabolic processes are affected by temperature, which may include the auditory system responses. To investigate the influence of temperature on turtle hearing, Trachemys scripta elegans was chosen to measure the peripheral hearing sensitivity at 10, 20, 30, and 40°C (close to the upper limit of heat resistance) using the auditory brainstem response (ABR) test. An increase in temperature (from 10 to 30°C) resulted in improved hearing sensitivity (a wider hearing sensitivity bandwidth, lower threshold, and shorter latency) in T. scripta elegans. At 40°C, the hearing sensitivity bandwidth continued to increase and the latency further shortened, but the threshold sensitivity reduced in the intermediate frequency range (0.5–0.8 kHz), increased in the high-frequency range (1.0–1.3 kHz), and did not significantly change in the low-frequency range (0.2–0.4 kHz) compared to that at 30°C. Our results suggest that although the hearing range of turtles is confined to lower frequencies than that in other animal groups, turtle hearing showed exceptional thermal regulation ability, especially when the temperature was close to the upper limit of heat resistance. Temperature increases that are sensitive to high frequencies imply that the males turtles’ auditory system adapts to a high-frequency sound environment in the context of global warming. Our study is expected to spur further research on the high-temperature plasticity of hearing sensitivity in diverse taxa or in the same group with different temperature ranges. Moreover, it facilitates forecasting the adaptive evolution of the auditory system to global warming.
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Tahara R, Larsson HCE. Paratympanic sinuses in juvenile Alligator. Anat Rec (Hoboken) 2022; 305:2926-2979. [PMID: 35591791 DOI: 10.1002/ar.24932] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 02/14/2022] [Accepted: 03/09/2022] [Indexed: 11/12/2022]
Abstract
Crocodylia has an extensive epithelial pneumatic space in the middle ear, paratympanic sinus system. Although fossil and extant crocodylian paratympanic sinus systems have been studied recently using the computed tomography (CT) and three-dimensional (3D) reconstruction data, due to the soft tissue nature of the pneumatic system and presence of its surrounding soft tissue structures, some boundaries, and definitions of each extension remain ambiguous. We describe the comprehensive paratympanic sinus system in posthatched alligator using soft tissue enhanced CT data with 3D reconstructions. The data are compared to the available data to discuss the ontogenetic pattern in alligator. We introduce further divided entities of the pneumatic system based on their associated bony and soft tissue structures and epithelial membrane and clarify the pneumatic terminologies. We then re-visit the potential homology of the paratympanic sinus in Archosauria. Epithelial boundaries of the ventral portion of the pneumatic system from the histological data suggest that the dual origin of the basioccipital diverticulum derived from the tympanic sinus and basicranial diverticulum medially. The presence of the epithelial boundary and pneumatic changes in ontogeny suggests that the middle ear may function differently in developmental stages. Lastly, a morphogenetic tree is constructed to help future work of comparative developmental studies of the paratympanic sinus system between crocodiles and birds.
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Affiliation(s)
- Rui Tahara
- Redpath Museum, McGill University, Montreal, Quebec, Canada
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7
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Pochat-Cottilloux Y, Martin JE, Jouve S, Perrichon G, Adrien J, Salaviale C, de Muizon C, Cespedes R, Amiot R. The neuroanatomy of Zulmasuchus querejazus (Crocodylomorpha, Sebecidae) and its implications for the paleoecology of sebecosuchians. Anat Rec (Hoboken) 2021; 305:2708-2728. [PMID: 34825786 DOI: 10.1002/ar.24826] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 09/07/2021] [Accepted: 09/29/2021] [Indexed: 01/14/2023]
Abstract
The endocranial structures of the sebecid crocodylomorph Zulmasuchus querejazus (MHNC 6672) from the Lower Paleocene of Bolivia are described in this article. Using computed tomography scanning, the cranial endocast, associated nerves and arteries, endosseous labyrinths, and cranial pneumatization are reconstructed and compared with those of extant and fossil crocodylomorphs, representative of different ecomorphological adaptations. Z. querejazus exhibits an unusual flexure of the brain, pericerebral spines, semicircular canals with a narrow diameter, as well as enlarged pharyngotympanic sinuses. First, those structures allow to estimate the alert head posture and hearing capabilities of Zulmasuchus. Then, functional comparisons are proposed between this purportedly terrestrial taxon, semi-aquatic, and aquatic forms (extant crocodylians, thalattosuchians, and dyrosaurids). The narrow diameter of the semicircular canals but expanded morphology of the endosseous labyrinths and the enlarged pneumatization of the skull compared to other forms indeed tend to indicate a terrestrial lifestyle for Zulmasuchus. Our results highlight the need to gather new data, especially from altirostral forms in order to further our understanding of the evolution of endocranial structures in crocodylomorphs with different ecomorphological adaptations.
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Affiliation(s)
| | - Jeremy E Martin
- Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, Villeurbanne, France
| | - Stéphane Jouve
- Centre de Recherche en Paléontologie - Paris (CR2P), Sorbonne Université, Paris, France
| | | | - Jérome Adrien
- Laboratoire Matériaux, Ingénierie et Science, Institut National des Sciences Appliquées de Lyon, Villeurbanne, France
| | - Céline Salaviale
- Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, Villeurbanne, France
| | - Christian de Muizon
- Centre de Recherche en Paléontologie - Paris (CR2P), Muséum National d'Histoire Naturelle, CNRS/MNHN/Sorbonne Université, Paris, France
| | - Ricardo Cespedes
- Museo de Historia Natural 'Alcide D'Orbigny', Cochabamba, Bolivia
| | - Romain Amiot
- Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, Villeurbanne, France
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8
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Morris ZS, Vliet KA, Abzhanov A, Pierce SE. Developmental origins of the crocodylian skull table and platyrostral face. Anat Rec (Hoboken) 2021; 305:2838-2853. [PMID: 34694063 DOI: 10.1002/ar.24802] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 09/13/2021] [Indexed: 11/10/2022]
Abstract
The dorsoventrally flattened skull typifies extant Crocodylia perhaps more than any other anatomical feature and is generally considered an adaptation for semi-aquatic feeding. Although the evolutionary origins of caniofacial flattening have been extensively studied, the developmental origins have yet to be explored. To understand how the skull table and platyrostral snout develop, we quantified embryonic development and post-hatching growth (ontogeny) of the crocodylian skull in lateral view using geometric morphometrics. Our dataset (n = 103) includes all but one extant genus and all of the major ecomorphs, including the extremely slender-snouted Gavialis and Tomistoma. Our analysis reveals that the embryonic development of the flattened skull is remarkably similar across ecomorphs, including the presence of a conserved initial embryonic skull shape, similar to prior analysis of dorsal snout shape. Although differences during posthatching ontogeny are recovered among ecomorphs, embryonic patterns are not distinct, revealing an important shift in developmental rate near hatching. In particular, the flattened skull table is achieved by the end of embryonic development with no changes after hatching. Further, the rotation of skull roof and facial bones during development is critical for the stereotypical flatness of the crocodylian skull. Our results suggest selection on hatchling performance and constraints on embryonic skull shape may have been important in this pattern of developmental conservation. The appearance of aspects of cranial flatness among Jurassic stem crocodylians suggests key aspects of these cranial developmental patterns may have been conserved for over 200 million years.
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Affiliation(s)
- Zachary S Morris
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Kent A Vliet
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Arhat Abzhanov
- Department of Life Sciences, Imperial College London, Berkshire, UK.,Natural History Museum, Cromwell Road, London, UK
| | - Stephanie E Pierce
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
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9
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New transitional fossil from late Jurassic of Chile sheds light on the origin of modern crocodiles. Sci Rep 2021; 11:14960. [PMID: 34294766 PMCID: PMC8298593 DOI: 10.1038/s41598-021-93994-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 06/09/2021] [Indexed: 11/08/2022] Open
Abstract
We describe the basal mesoeucrocodylian Burkesuchus mallingrandensis nov. gen. et sp., from the Upper Jurassic (Tithonian) Toqui Formation of southern Chile. The new taxon constitutes one of the few records of non-pelagic Jurassic crocodyliforms for the entire South American continent. Burkesuchus was found on the same levels that yielded titanosauriform and diplodocoid sauropods and the herbivore theropod Chilesaurus diegosuarezi, thus expanding the taxonomic composition of currently poorly known Jurassic reptilian faunas from Patagonia. Burkesuchus was a small-sized crocodyliform (estimated length 70 cm), with a cranium that is dorsoventrally depressed and transversely wide posteriorly and distinguished by a posteroventrally flexed wing-like squamosal. A well-defined longitudinal groove runs along the lateral edge of the postorbital and squamosal, indicative of a anteroposteriorly extensive upper earlid. Phylogenetic analysis supports Burkesuchus as a basal member of Mesoeucrocodylia. This new discovery expands the meagre record of non-pelagic representatives of this clade for the Jurassic Period, and together with Batrachomimus, from Upper Jurassic beds of Brazil, supports the idea that South America represented a cradle for the evolution of derived crocodyliforms during the Late Jurassic.
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10
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Russell AP, Bauer AM. Vocalization by extant nonavian reptiles: A synthetic overview of phonation and the vocal apparatus. Anat Rec (Hoboken) 2020; 304:1478-1528. [PMID: 33099849 DOI: 10.1002/ar.24553] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 08/13/2020] [Accepted: 09/16/2020] [Indexed: 12/19/2022]
Abstract
Among amniote vertebrates, nonavian reptiles (chelonians, crocodilians, and lepidosaurs) are regarded as using vocal signals rarely (compared to birds and mammals). In all three reptilian clades, however, certain taxa emit distress calls and advertisement calls using modifications of regions of the upper respiratory tract. There is no central tendency in either acoustic mechanisms or the structure of the vocal apparatus, and many taxa that vocalize emit only relatively simple sounds. Available evidence indicates multiple origins of true vocal abilities within these lineages. Reptiles thus provide opportunities for studying the early evolutionary stages of vocalization. The early literature on the diversity of form of the laryngotracheal apparatus of reptiles boded well for the study of form-function relationships, but this potential was not extensively explored. Emphasis shifted away from anatomy, however, and centered instead on acoustic analysis of the sounds that are produced. New investigative techniques have provided novel ways of studying the form-function aspects of the structures involved in phonation and have brought anatomical investigation to the forefront again. In this review we summarize what is known about hearing in reptiles in order to contextualize the vocal signals they generate and the sound-producing mechanisms responsible for them. The diversity of form of the sound producing apparatus and the increasing evidence that reptiles are more dependent upon vocalization as a communication medium than previously thought indicates that they have a significant role to play in the understanding of the evolution of vocalization in amniotes.
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Affiliation(s)
- Anthony P Russell
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Aaron M Bauer
- Department of Biology and Center for Biodiversity and Ecosystem Stewardship, Villanova University, Villanova, Pennsylvania, USA
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11
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Christensen-Dalsgaard J, Lee N, Bee MA. Lung-to-ear sound transmission does not improve directional hearing in green treefrogs ( Hyla cinerea). J Exp Biol 2020; 223:jeb232421. [PMID: 32895324 DOI: 10.1242/jeb.232421] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 08/26/2020] [Indexed: 11/20/2022]
Abstract
Amphibians are unique among extant vertebrates in having middle ear cavities that are internally coupled to each other and to the lungs. In frogs, the lung-to-ear sound transmission pathway can influence the tympanum's inherent directionality, but what role such effects might play in directional hearing remains unclear. In this study of the American green treefrog (Hyla cinerea), we tested the hypothesis that the lung-to-ear sound transmission pathway functions to improve directional hearing, particularly in the context of intraspecific sexual communication. Using laser vibrometry, we measured the tympanum's vibration amplitude in females in response to a frequency modulated sweep presented from 12 sound incidence angles in azimuth. Tympanum directionality was determined across three states of lung inflation (inflated, deflated, reinflated) both for a single tympanum in the form of the vibration amplitude difference (VAD) and for binaural comparisons in the form of the interaural vibration amplitude difference (IVAD). The state of lung inflation had negligible effects (typically less than 0.5 dB) on both VADs and IVADs at frequencies emphasized in the advertisement calls produced by conspecific males (834 and 2730 Hz). Directionality at the peak resonance frequency of the lungs (1558 Hz) was improved by ∼3 dB for a single tympanum when the lungs were inflated versus deflated, but IVADs were not impacted by the state of lung inflation. Based on these results, we reject the hypothesis that the lung-to-ear sound transmission pathway functions to improve directional hearing in frogs.
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Affiliation(s)
| | - Norman Lee
- Department of Biology, St Olaf College, Northfield, MN 55057, USA
| | - Mark A Bee
- Department of Ecology, Evolution, and Behavior, University of Minnesota - Twin Cities, St Paul, MN 55126, USA
- Graduate Program in Neuroscience, University of Minnesota - Twin Cities, Minneapolis, MN 55455, USA
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12
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Papet L, Raymond M, Boyer N, Mathevon N, Grimault N. Crocodiles use both interaural level differences and interaural time differences to locate a sound source. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 148:EL307. [PMID: 33138473 DOI: 10.1121/10.0001979] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 08/27/2020] [Indexed: 06/11/2023]
Abstract
To explore how crocodilians locate a sound source, two Nile crocodiles (Crocodylus niloticus) were trained to swim towards an acoustic target. Using filtered versions of synthesized stimuli, the respective roles of interaural level differences (ILDs) and interaural time differences (ITDs), which are the two main cues providing information on sound source position, were tested. This study shows that crocodiles rely on both ILDs and ITDs to locate the spatial direction of a sound source and that their performance is lower when one of the cues is lacking.
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Affiliation(s)
- L Papet
- Equipe Cognition Auditive et Psychoacoustique, Centre de Recherche en Neurosciences de Lyon, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5292, Institut National de la Santé et de la Recherche Médicale U1028, Université Lyon 1, Lyon, France
| | - M Raymond
- Equipe Cognition Auditive et Psychoacoustique, Centre de Recherche en Neurosciences de Lyon, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5292, Institut National de la Santé et de la Recherche Médicale U1028, Université Lyon 1, Lyon, France
| | - N Boyer
- Equipe Cognition Auditive et Psychoacoustique, Centre de Recherche en Neurosciences de Lyon, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5292, Institut National de la Santé et de la Recherche Médicale U1028, Université Lyon 1, Lyon, France
| | - N Mathevon
- Equipe Cognition Auditive et Psychoacoustique, Centre de Recherche en Neurosciences de Lyon, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5292, Institut National de la Santé et de la Recherche Médicale U1028, Université Lyon 1, Lyon, France
| | - N Grimault
- Equipe Cognition Auditive et Psychoacoustique, Centre de Recherche en Neurosciences de Lyon, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5292, Institut National de la Santé et de la Recherche Médicale U1028, Université Lyon 1, Lyon, , , , ,
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13
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Wang T, Li H, Cui J, Zhai X, Shi H, Wang J. Auditory brainstem responses in the red-eared slider Trachemys scripta elegans (Testudoformes: Emydidae) reveal sexually dimorphic hearing sensitivity. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:847-854. [PMID: 31654192 PMCID: PMC6863946 DOI: 10.1007/s00359-019-01372-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 09/04/2019] [Accepted: 10/09/2019] [Indexed: 11/26/2022]
Abstract
Hearing sensitivity is of general interest from the perspective of understanding the functionality and evolution of vertebrate auditory systems. Sexual dimorphism of auditory systems has been reported in several species of vertebrates, but little is known about this phenomenon in turtles. Some morphological characteristics, such as middle ear and tympanic membrane that influence the hearing sensitivity of animals can result in hearing sexual dimorphism. To examine whether sexual dimorphism in hearing sensitivity occurs in turtles and to compare hearing characteristics with respect to the shape of the tympanic membrane, we measured the hearing sensitivity and tympanum diameter in both sexes of Trachemys scripta elegans. The results showed that, with the exception of 0.9 kHz, auditory brainstem response thresholds were significantly lower in females than in males for frequencies in the 0.2-1.1 kHz range, indicating that the hearing of females shows greater sensitivity. No significant differences were detected in the tympanum diameter of both sexes. These results showed that sexually dimorphic hearing sensitivity has evolved in turtles; however, this difference does not appear to be related to differences in the size of the tympanic membrane. The possible origin and function of the sexual differences in auditory characteristic are discussed.
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Affiliation(s)
- Tongliang Wang
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou, China
| | - Handong Li
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou, China
| | - Jianguo Cui
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Xiaofei Zhai
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou, China
| | - Haitao Shi
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou, China
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Jichao Wang
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou, China.
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Papet L, Grimault N, Boyer N, Mathevon N. Influence of head morphology and natural postures on sound localization cues in crocodilians. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190423. [PMID: 31417740 PMCID: PMC6689610 DOI: 10.1098/rsos.190423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 05/31/2019] [Indexed: 06/10/2023]
Abstract
As top predators, crocodilians have an acute sense of hearing that is useful for their social life and for probing their environment in hunting situations. Although previous studies suggest that crocodilians are able to localize the position of a sound source, how they do this remains largely unknown. In this study, we measured the potential monaural sound localization cues (head-related transfer functions; HRTFs) on alive animals and skulls in two situations, both mimicking natural positions: basking on the land and cruising at the interface between air and water. Binaural cues were also estimated by measuring the interaural level differences (ILDs) and the interaural time differences (ITDs). In both conditions, HRTF measurements show large spectral variations (greater than 10 dB) for high frequencies, depending on the azimuthal angle. These localization cues are influenced by head size and by the internal coupling of the ears. ITDs give reliable information regarding sound-source position for low frequencies, while ILDs are more suitable for frequencies higher than 1.5 kHz. Our results support the hypothesis that crocodilian head morphology is adapted to acquire reliable localization cues from sound sources when outside the water, but also when only a small part of their head is above the air-water interface.
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Affiliation(s)
- L. Papet
- Centre de Recherche en Neurosciences de Lyon – Equipe Cognition Auditive et Psychoacoustique, CNRS UMR 5292, Univ. Lyon 1, Lyon, France
- Equipe Neuro-Ethologie Sensorielle ENES/NeuroPSI, CNRS UMR 9197, University of Lyon, Saint-Etienne, France
| | - N. Grimault
- Centre de Recherche en Neurosciences de Lyon – Equipe Cognition Auditive et Psychoacoustique, CNRS UMR 5292, Univ. Lyon 1, Lyon, France
| | - N. Boyer
- Equipe Neuro-Ethologie Sensorielle ENES/NeuroPSI, CNRS UMR 9197, University of Lyon, Saint-Etienne, France
| | - N. Mathevon
- Equipe Neuro-Ethologie Sensorielle ENES/NeuroPSI, CNRS UMR 9197, University of Lyon, Saint-Etienne, France
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15
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Köppl C. Internally coupled middle ears enhance the range of interaural time differences heard by the chicken. ACTA ACUST UNITED AC 2019; 222:jeb.199232. [PMID: 31138639 DOI: 10.1242/jeb.199232] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 04/30/2019] [Indexed: 11/20/2022]
Abstract
Interaural time differences (ITDs) are one of several principal cues for localizing sounds. However, ITDs are in the sub-millisecond range for most animals. Because the neural processing of such small ITDs pushes the limit of temporal resolution, the precise ITD range for a given species and its usefulness - relative to other localization cues - has been a powerful selective force in the evolution of the neural circuits involved. Birds and other non-mammals have internally coupled middle ears working as pressure-difference receivers that may significantly enhance ITDs, depending on the precise properties of the interaural connection. Here, the extent of this internal coupling was investigated in chickens, specifically under the same experimental conditions as typically used in investigations of the neurophysiology of ITD-coding circuits, i.e. with headphone stimulation and skull openings. Cochlear microphonics (CM) were recorded simultaneously from both ears of anesthetized chickens under monaural and binaural stimulation, using pure tones from 0.1 to 3 kHz. Interaural transmission peaked at 1.5 kHz at a loss of only -5.5 dB; the mean interaural delay was 264 µs. CM amplitude was strongly modulated as a function of ITD, confirming significant interaural coupling. The 'ITD heard' derived from the CM phases in both ears showed enhancement, compared with the acoustic stimuli, by a factor of up to 1.8. However, the experimental conditions impaired interaural transmission at low frequencies (<1 kHz). I identify factors that need to be considered when interpreting neurophysiological data obtained under these conditions and relating them to the natural free-field condition.
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Affiliation(s)
- Christine Köppl
- Department of Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany .,Cluster of Excellence "Hearing4all" and Research Center Neurosensory Science, Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany
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16
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Kettler L, Carr CE. Neural Maps of Interaural Time Difference in the American Alligator: A Stable Feature in Modern Archosaurs. J Neurosci 2019; 39:3882-3896. [PMID: 30886018 PMCID: PMC6520516 DOI: 10.1523/jneurosci.2989-18.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 02/20/2019] [Accepted: 02/23/2019] [Indexed: 11/21/2022] Open
Abstract
Detection of interaural time differences (ITDs) is crucial for sound localization in most vertebrates. The current view is that optimal computational strategies of ITD detection depend mainly on head size and available frequencies, although evolutionary history should also be taken into consideration. In archosaurs, which include birds and crocodiles, the brainstem nucleus laminaris (NL) developed into the critical structure for ITD detection. In birds, ITDs are mapped in an orderly array or place code, whereas in the mammalian medial superior olive, the analog of NL, maps are not found. As yet, in crocodilians, topographical representations have not been identified. However, nontopographic representations of ITD cannot be excluded due to different anatomical and ethological features of birds and crocodiles. Therefore, we measured ITD-dependent responses in the NL of anesthetized American alligators of either sex and identified the location of the recording sites by lesions made after recording. The measured extracellular field potentials, or neurophonics, were strongly ITD tuned, and their preferred ITDs correlated with the position in NL. As in birds, delay lines, which compensate for external time differences, formed maps of ITD. The broad distributions of best ITDs within narrow frequency bands were not consistent with an optimal coding model. We conclude that the available acoustic cues and the architecture of the acoustic system in early archosaurs led to a stable and similar organization in today's birds and crocodiles, although physical features, such as internally coupled ears, head size, or shape, and audible frequency range, vary among the two groups.SIGNIFICANCE STATEMENT Interaural time difference (ITD) is an important cue for sound localization, and the optimal strategies for encoding ITD in neuronal populations are the subject of ongoing debate. We show that alligators form maps of ITD very similar to birds, suggesting that their common archosaur ancestor reached a stable coding solution different from mammals. Mammals and diapsids evolved tympanic hearing independently, and local optima can be reached in evolution that are not considered by global optimal coding models. Thus, the presence of ITD maps in the brainstem may reflect a local optimum in evolutionary development. Our results underline the importance of comparative animal studies and show that optimal models must be viewed in the light of evolutionary processes.
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Affiliation(s)
- Lutz Kettler
- Lehrstuhl für Zoologie, Technische Universität München, 85354 Freising, Germany, and
| | - Catherine E Carr
- Department of Biology, University of Maryland, College Park, Maryland 20742
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17
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Affiliation(s)
- Rui Tahara
- Redpath Museum, McGill University, Montreal, Quebec, Canada
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18
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Young BA, Bierman HS. On the median pharyngeal valve of the American alligator (Alligator mississippiensis). J Morphol 2018; 280:58-67. [PMID: 30515863 DOI: 10.1002/jmor.20914] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 09/22/2018] [Accepted: 10/13/2018] [Indexed: 12/20/2022]
Abstract
The middle ear cavities of crocodilians have complex connections with the pharyngeal lumen, including lateral and median components which both open into a single chamber located on the dorsal midline of the pharynx. This chamber and the surrounding soft-tissue is herein termed the median pharyngeal valve. In the American alligator (Alligator mississippiensis) this valve opens, for a duration of 0.3 s, approximately every 120 s; the patency of the median pharyngeal valve was not influenced by either auditory stimuli or by submersing the alligator underwater. The median pharyngeal valve has an outer capsule of dense connective tissue and fibrocartilage and an inner "plug" of loose connective tissue. These opposing surfaces are lined by respiratory epithelium and separated by a cavity that is continuous with the middle ear cavities and the pharyngeal lumen (through a central opening in the capsule termed the pore). The inner plug of the median pharyngeal valve is contacted by skeletal muscles positioned to serve as both elevators/retractors (which would open the valve) and elevators/protractors (which, in conjunction with gravity, would close the valve). Unlike other vertebrate valve systems, the median pharyngeal valve appears to function as a deformable ball check valve.
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Affiliation(s)
- Bruce A Young
- Department of Anatomy, Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, Missouri
| | - Hilary S Bierman
- Department of Biology, University of Maryland, College Park, Maryland
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19
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Herrera Y, Leardi JM, Fernández MS. Braincase and endocranial anatomy of two thalattosuchian crocodylomorphs and their relevance in understanding their adaptations to the marine environment. PeerJ 2018; 6:e5686. [PMID: 30515353 PMCID: PMC6263203 DOI: 10.7717/peerj.5686] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/30/2018] [Indexed: 11/29/2022] Open
Abstract
Thalattosuchians are a group of Mesozoic crocodylomorphs known from aquatic deposits of the Early Jurassic–Early Cretaceous that comprises two main lineages of almost exclusively marine forms, Teleosauridae and Metriorhynchoidea. Teleosaurids were found in shallow marine, brackish and freshwater deposits, and have been characterized as semiaquatic near-shore forms, whereas metriorhynchids are a lineage of fully pelagic forms, supported by a large set of morphological characters of the skull and postcranial anatomy. Recent contributions on Thalattosuchia have been focused on the study of the endocranial anatomy. This newly available information provides novel evidence to suggest adaptations on the neuroanatomy, senses organs, vasculature, and behavioral evolution of these crocodylomorphs. However, is still not clear if the major morphological differences between teleosaurids and metriorhynchids were also mirrored by changes in the braincase and endocranial anatomy. Based on X-ray CT scanning and digital endocast reconstructions we describe the braincase and endocranial anatomy of two well-preserved specimens of Thalattosuchia, the semiaquatic teleosaurid Steneosaurus bollensis and the pelagic metriorhynchid Cricosaurus araucanensis. We propose that some morphological traits, such as: an enlarged foramen for the internal carotid artery, a carotid foramen ventral to the occipital condyle, a single CN XII foramen, absence of brain flexures, well-developed cephalic vascular system, lack of subtympanic foramina and the reduction of the paratympanic sinus system, are distinctive features of Thalattosuchia. It has been previously suggested that the enlarged foramen for the internal carotid artery, the absence of brain flexures, and the hypertrophied cephalic vascular system were synapomorphies of Metriorhynchidae; however, new information revealed that all of these features were already established at the base of Thalattosuchia and might have been exapted later on their evolutionary history. Also, we recognized some differences within Thalattosuchia that previously have not been received attention or even were overlooked (e.g., circular/bilobate trigeminal foramen, single/double CN XII foramen, separation of the cranioquadrate canal from the external otic aperture, absence/presence of lateral pharyngeal foramen). The functional significances of these traits are still unclear. Extending the sampling to other Thalattosuchia will help to test the timing of acquisition and distribution of these morphological modifications among the whole lineage. Also comparison with extant marine tetrapods (including physiological information) will be crucial to understand if some (and/or which) of the morphological peculiarities of thalattosuchian braincases are products of directional natural selection resulting in a fully adaptation to a nektonic life style.
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Affiliation(s)
- Yanina Herrera
- CONICET. División Paleontología Vertebrados, Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - Juan Martín Leardi
- CONICET. Instituto de Estudios Andinos "Don Pablo Groeber" (IDEAN), Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias Geológicas, Universidad de Buenos Aires, Buenos Aires, Argentina.,Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Facultad de Ciencias Exactas y Naturales, Departamento de Biodiversidad y Biología Experimental, Universidad de Buenos Aires, Argentina
| | - Marta S Fernández
- CONICET. División Paleontología Vertebrados, Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
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20
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Brandt C, Brande-Lavridsen N, Christensen-Dalsgaard J. The Masked ABR (mABR): a New Measurement Method for the Auditory Brainstem Response. J Assoc Res Otolaryngol 2018; 19:753-761. [PMID: 30238407 DOI: 10.1007/s10162-018-00696-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Accepted: 09/04/2018] [Indexed: 11/26/2022] Open
Abstract
The auditory brainstem response (ABR) is relatively non-invasive, and in many species, the only practical way to assess auditory sensitivity. The two main methods for measuring ABR are using either transients or tone bursts as a stimulus. The transient stimulus produces strong neural responses that contain no frequency information. In contrast, tone bursts stimulate only a small part of the auditory system, eliciting weaker neural responses but supplying frequency information. Furthermore, short tone bursts become less and less frequency specific with increasing stimulus wavelength, making them unsuitable for testing low-frequency hearing. Here, we develop a method that can measure sensitivity to both low and high-frequency stimuli. The method is based on masking of a transient response by long-duration sinusoids. The measurement system is developed as a highly portable system that runs on battery power. It has been used in a variety of animals in our lab and in the field, including squid (Mooney et al. in J Exp Biol 213: 3748-3759, 2010), lungfish (Christensen-Dalsgaard et al. in J Neurophys 105: 1992-2004, 2011b), alligators (Bierman et al. in J Exp Biol 217: 1094-1107, 2014), and mink (Brandt et al. in J Exp Biol 216: 3542-3550, 2013). Here, we present data recorded from Tokay geckos and compare the results with tone burst ABR measurements. This method produces results comparable to tone burst stimulations at higher frequencies (above 1 kHz) but has several advantages: it is relatively insensitive to fluctuations in neural signal level, it allows measurements at very low frequencies, it allows constant monitoring of the state of the animal, and can be used to measure directional hearing.
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Affiliation(s)
- Christian Brandt
- Institute of Clinical Research, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
- Institute of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
| | - Nanna Brande-Lavridsen
- Institute of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
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21
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Biophysical heterogeneity in the tympanic membrane of the Asian water monitor lizard, Varanus salvator. ZOOMORPHOLOGY 2018. [DOI: 10.1007/s00435-018-0396-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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22
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Walton PL, Christensen-Dalsgaard J, Carr C. Evolution of Sound Source Localization Circuits in the Nonmammalian Vertebrate Brainstem. BRAIN, BEHAVIOR AND EVOLUTION 2017; 90:131-153. [PMID: 28988244 PMCID: PMC5691234 DOI: 10.1159/000476028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 04/25/2017] [Indexed: 12/31/2022]
Abstract
The earliest vertebrate ears likely subserved a gravistatic function for orientation in the aquatic environment. However, in addition to detecting acceleration created by the animal's own movements, the otolithic end organs that detect linear acceleration would have responded to particle movement created by external sources. The potential to identify and localize these external sources may have been a major selection force in the evolution of the early vertebrate ear and in the processing of sound in the central nervous system. The intrinsic physiological polarization of sensory hair cells on the otolith organs confers sensitivity to the direction of stimulation, including the direction of particle motion at auditory frequencies. In extant fishes, afferents from otolithic end organs encode the axis of particle motion, which is conveyed to the dorsal regions of first-order octaval nuclei. This directional information is further enhanced by bilateral computations in the medulla and the auditory midbrain. We propose that similar direction-sensitive neurons were present in the early aquatic tetrapods and that selection for sound localization in air acted upon preexisting brain stem circuits like those in fishes. With movement onto land, the early tetrapods may have retained some sensitivity to particle motion, transduced by bone conduction, and later acquired new auditory papillae and tympanic hearing. Tympanic hearing arose in parallel within each of the major tetrapod lineages and would have led to increased sensitivity to a broader frequency range and to modification of the preexisting circuitry for sound source localization.
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Affiliation(s)
| | | | - Catherine Carr
- Department of Biology, University of Maryland, College Park MD, 20742-4415, USA
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23
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Kettler L, Christensen-Dalsgaard J, Larsen ON, Wagner H. Low frequency eardrum directionality in the barn owl induced by sound transmission through the interaural canal. BIOLOGICAL CYBERNETICS 2016; 110:333-343. [PMID: 27209198 DOI: 10.1007/s00422-016-0689-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 05/09/2016] [Indexed: 05/22/2023]
Abstract
The middle ears of birds are typically connected by interaural cavities that form a cranial canal. Eardrums coupled in this manner may function as pressure difference receivers rather than pressure receivers. Hereby, the eardrum vibrations become inherently directional. The barn owl also has a large interaural canal, but its role in barn owl hearing and specifically in sound localization has been controversial so far. We discuss here existing data and the role of the interaural canal in this species and add a new dataset obtained by laser Doppler vibrometry in a free-field setting. Significant sound transmission across the interaural canal occurred at low frequencies. The sound transmission induces considerable eardrum directionality in a narrow band from 1.5 to 3.5 kHz. This is below the frequency range used by the barn owl for locating prey, but may conceivably be used for locating conspecific callers.
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Affiliation(s)
- Lutz Kettler
- Department of Biology, Center for Comparative and Evolutionary Biology of Hearing, University of Maryland College Park, College Park, MD, 20742, USA.
- Department of Zoology and Animal Physiology, Institute of Biology II, RWTH Aachen, Worringerweg 3, 52074, Aachen, Germany.
| | | | - Ole Næsbye Larsen
- Department of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Hermann Wagner
- Department of Zoology and Animal Physiology, Institute of Biology II, RWTH Aachen, Worringerweg 3, 52074, Aachen, Germany
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24
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Mason MJ. Internally coupled ears in living mammals. BIOLOGICAL CYBERNETICS 2016; 110:345-358. [PMID: 26794500 PMCID: PMC5107206 DOI: 10.1007/s00422-015-0675-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 12/11/2015] [Indexed: 05/22/2023]
Abstract
It is generally held that the right and left middle ears of mammals are acoustically isolated from each other, such that mammals must rely on neural computation to derive sound localisation cues. There are, however, some unusual species in which the middle ear cavities intercommunicate, in which case each ear might be able to act as a pressure-difference receiver. This could improve sound localisation at lower frequencies. The platypus Ornithorhynchus is apparently unique among mammals in that its tympanic cavities are widely open to the pharynx, a morphology resembling that of some non-mammalian tetrapods. The right and left middle ear cavities of certain talpid and golden moles are connected through air passages within the basicranium; one experimental study on Talpa has shown that the middle ears are indeed acoustically coupled by these means. Having a basisphenoid component to the middle ear cavity walls could be an important prerequisite for the development of this form of interaural communication. Little is known about the hearing abilities of platypus, talpid and golden moles, but their audition may well be limited to relatively low frequencies. If so, these mammals could, in principle, benefit from the sound localisation cues available to them through internally coupled ears. Whether or not they actually do remains to be established experimentally.
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Affiliation(s)
- Matthew J Mason
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
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25
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Larsen ON, Christensen-Dalsgaard J, Jensen KK. Role of intracranial cavities in avian directional hearing. BIOLOGICAL CYBERNETICS 2016; 110:319-331. [PMID: 27209199 DOI: 10.1007/s00422-016-0688-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 05/03/2016] [Indexed: 05/22/2023]
Abstract
Whereas it is clear from anatomical studies that all birds have complex interaural canals connecting their middle ears, the effect of interaural coupling on directional hearing has been disputed. A reason for conflicting results in earlier studies may have been that the function of the tympanic ear and hence of the interaural coupling is sensitive to variations in the intracranial air pressure. In awake birds, the middle ears and connected cavities are vented actively through the pharyngotympanic tube. This venting reflex seems to be suppressed in anesthetized birds, leading to increasingly lower pressure in the interaural cavities, stiffening the eardrums, and displacing them medially. This causes the sensitivity, as well as the interaural coupling, to drop. Conversely, when the middle ears are properly vented, robust directional eardrum responses, most likely caused by internal coupling, have been reported. The anatomical basis of this coupling is the 'interaural canal,' which turns out to be a highly complex canal and cavity system, which we describe for the zebra finch. Surprisingly, given the complexity of the interaural canals, simple models of pipe-coupled middle ears fit the eardrum directionality data quite well, but future models taking the complex anatomy into consideration should be developed.
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Affiliation(s)
- Ole Næsbye Larsen
- Department of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark.
| | | | - Kenneth Kragh Jensen
- Starkey Hearing Technologies, 6600 Washington Ave. S, Eden Prairie, MN, 55344, USA
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26
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Young BA. Anatomical influences on internally coupled ears in reptiles. BIOLOGICAL CYBERNETICS 2016; 110:255-261. [PMID: 27699482 DOI: 10.1007/s00422-016-0699-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 09/17/2016] [Indexed: 05/22/2023]
Abstract
Many reptiles, and other vertebrates, have internally coupled ears in which a patent anatomical connection allows pressure waves generated by the displacement of one tympanic membrane to propagate (internally) through the head and, ultimately, influence the displacement of the contralateral tympanic membrane. The pattern of tympanic displacement caused by this internal coupling can give rise to novel sensory cues. The auditory mechanics of reptiles exhibit more anatomical variation than in any other vertebrate group. This variation includes structural features such as diverticula and septa, as well as coverings of the tympanic membrane. Many of these anatomical features would likely influence the functional significance of the internal coupling between the tympanic membranes. Several of the anatomical components of the reptilian internally coupled ear are under active motor control, suggesting that in some reptiles the auditory system may be more dynamic than previously recognized.
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Affiliation(s)
- Bruce A Young
- Department of Anatomy, Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, MO, 63501, USA.
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27
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Carr CE, Christensen-Dalsgaard J, Bierman H. Coupled ears in lizards and crocodilians. BIOLOGICAL CYBERNETICS 2016; 110:291-302. [PMID: 27734148 PMCID: PMC6003244 DOI: 10.1007/s00422-016-0698-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Accepted: 09/17/2016] [Indexed: 05/22/2023]
Abstract
Lizard ears are coupled across the pharynx, and are very directional. In consequence all auditory responses should be directional, without a requirement for computation of sound source location. Crocodilian ears are connected through sinuses, and thus less tightly coupled. Coupling may improve the processing of low-frequency directional signals, while higher frequency signals appear to be progressively uncoupled. In both lizards and crocodilians, the increased directionality of the coupled ears leads to an effectively larger head and larger physiological range of ITDs. This increased physiological range is reviewed in the light of current theories of sound localization.
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Affiliation(s)
- Catherine E Carr
- Department of Biology, University of Maryland College Park, College Park, MD, 20742, USA.
| | | | - Hilary Bierman
- Department of Biology, University of Maryland College Park, College Park, MD, 20742, USA
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28
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Han D, Young BA. Anatomical Basis of Dynamic Modulation of Tympanic Tension in the Water Monitor Lizard, Varanus salvator. Anat Rec (Hoboken) 2016; 299:1270-80. [PMID: 27312415 DOI: 10.1002/ar.23382] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 04/09/2016] [Accepted: 04/26/2016] [Indexed: 11/09/2022]
Abstract
Amphibious vertebrates, such as the water monitor (Varanus salvator), require anatomical and/or neural specializations to cope with pressure changes on the tympanic membrane when transiting between air and water. V. salvator has internally coupled ears which are distinguished by (patent) anatomical conduits through the skull linking the middle ear cavities on both sides of the head. We describe a small skeletal muscle in V. salvator which inserts onto the middle ear ossicle and the tympanic membrane. Laser doppler vibrometry demonstrates that contraction of this muscle both increases the vibrational velocity of the tympanic membrane and changes the waveform pattern of the tympanic displacement. The combined anatomical and functional results suggest that V. salvator is capable of actively modulating the tension of the tympanic membrane. Anat Rec, 299:1270-1280, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Dawei Han
- Department of Anatomy, Kirksville College of Osteopathic Medicine/Missouri School of Dentistry and Oral Health, A.T. Still University, Kirksville, Missouri
| | - Bruce A Young
- Department of Anatomy, Kirksville College of Osteopathic Medicine/Missouri School of Dentistry and Oral Health, A.T. Still University, Kirksville, Missouri
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29
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Montefeltro FC, Andrade DV, Larsson HCE. The evolution of the meatal chamber in crocodyliforms. J Anat 2016; 228:838-63. [PMID: 26843096 DOI: 10.1111/joa.12439] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2015] [Indexed: 11/27/2022] Open
Abstract
The unique outer ear of crocodylians consists of a large meatal chamber (MC) concealed by a pair of muscular earlids that shape a large part of the animal's head. This chamber is limited medially by the enlarged tympanic membrane. Yet, the anatomy of this distinctive and complex region is underexplored and its evolutionary history untraced. The osteology and soft tissues of the MC in extant crocodylians was analysed to describe it and establish osteological correlates within this region. A broad survey of the osteological correlates was conducted in major clades of fossil crocodyliforms to estimate evolutionary trends of the MC. The reorganization of the MC at the origin of crocodyliforms includes characters also present in more basal taxa such as 'sphenosuchians' as well as unique traits of crocodyliforms. Three major patterns are recognized in the MC of basal mesoeucrocodylians. The distinct 'thalattosuchian pattern' indicates that extensive modifications occurred in this clade of aquatic fossil crocodyliforms, even when multiple alternative phylogenetic positions are taken into account. Some traits already established in putative closely related clades are absent or modified in this group. The 'basal notosuchian/sebecian pattern' is widespread among basal metasuchians, and establishes for the first time characters maintained later in neosuchians and extant forms. The 'advanced notosuchian pattern' includes modifications of the MC possibly related to a terrestrial lifestyle and potentially a structure analogous to the mammalian pinna. The main variation in the MC of neosuchians is associated with the homoplastic secondary opening of the cranioquadrate passage. The inferred phylogenetic trends in the crocodyliform MC suggest the great anatomical disparity in this region followed a complex evolutionary pattern, and tympanic hearing played an important role in the origin and diversification of Crocodyliformes.
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Affiliation(s)
- Felipe C Montefeltro
- Departamento de Biologia e Zootecnia, FEIS-UNESP, Ilha Solteira, São Paulo, Brazil
| | - Denis V Andrade
- Departamento de Zoologia, UNESP, Rio Claro, São Paulo, Brazil
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Carr CE, Christensen-Dalsgaard J. Sound Localization Strategies in Three Predators. BRAIN, BEHAVIOR AND EVOLUTION 2015; 86:17-27. [PMID: 26398572 DOI: 10.1159/000435946] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In this paper, we compare some of the neural strategies for sound localization and encoding interaural time differences (ITDs) in three predatory species of Reptilia, alligators, barn owls and geckos. Birds and crocodilians are sister groups among the extant archosaurs, while geckos are lepidosaurs. Despite the similar organization of their auditory systems, archosaurs and lizards use different strategies for encoding the ITDs that underlie localization of sound in azimuth. Barn owls encode ITD information using a place map, which is composed of neurons serving as labeled lines tuned for preferred spatial locations, while geckos may use a meter strategy or population code composed of broadly sensitive neurons that represent ITD via changes in the firing rate.
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Affiliation(s)
- Catherine E Carr
- Department of Biology, University of Maryland Center for the Comparative and Evolutionary Biology of Hearing, College Park, Md., USA
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31
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Dufeau DL, Witmer LM. Ontogeny of the Middle-Ear Air-Sinus System in Alligator mississippiensis (Archosauria: Crocodylia). PLoS One 2015; 10:e0137060. [PMID: 26398659 PMCID: PMC4580574 DOI: 10.1371/journal.pone.0137060] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 08/12/2015] [Indexed: 01/05/2023] Open
Abstract
Modern crocodylians, including Alligator mississippiensis, have a greatly elaborated system of pneumatic sinuses invading the cranium. These sinuses invade nearly all the bones of the chondrocranium and several bony elements of the splanchnocranium, but patterns of postnatal paratympanic sinus development are poorly understood and documented. Much of crocodylomorph--indeed archosaurian--evolution is characterized by the evolution of various paratympanic air sinuses, the homologies of which are poorly understood due in large part to the fact that individual sinuses tend to become confluent in adults, obscuring underlying patterns. This study seeks to explore the ontogeny of these sinuses primarily to clarify the anatomical relations of the individual sinuses before they become confluent and thus to provide the foundation for later studies testing hypotheses of homology across extant and extinct Archosauria. Ontogeny was assessed using computed tomography in a sample of 13 specimens covering an almost 19-fold increase in head size. The paratympanic sinus system comprises two major inflations of evaginated pharyngeal epithelium: the pharyngotympanic sinus, which communicates with the pharynx via the lateral (true) Eustachian tubes and forms the cavum tympanicum proprium, and the median pharyngeal sinus, which communicates with the pharynx via the median pharyngeal tube. Each of these primary inflations gives rise to a number of secondary inflations that further invade the bones of the skull. The primary sinuses and secondary diverticula are well developed in perinatal individuals of Alligator, but during ontogeny the number and relative volumes of the secondary diverticula are reduced. In addition to describing the morphological ontogeny of this sinus system, we provide some preliminary exploratory analyses of sinus function and allometry, rejecting the hypothesis that changes in the volume of the paratympanic sinuses are simply an allometric function of braincase volume, but instead support the hypothesis that these changes may be a function of the acoustic properties of the middle ear.
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Affiliation(s)
- David L. Dufeau
- Department of Biological Sciences, Ohio University, Athens, Ohio, United States of America
- * E-mail:
| | - Lawrence M. Witmer
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America
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Blanco A, Fortuny J, Vicente A, Luján ÀH, García-Marçà JA, Sellés AG. A new species of Allodaposuchus (Eusuchia, Crocodylia) from the Maastrichtian (Late Cretaceous) of Spain: phylogenetic and paleobiological implications. PeerJ 2015; 3:e1171. [PMID: 26339549 PMCID: PMC4558081 DOI: 10.7717/peerj.1171] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 07/20/2015] [Indexed: 11/20/2022] Open
Abstract
Background. The Late Cretaceous is a keystone period to understand the origin and early radiation of Crocodylia, the group containing all extant lineages of crocodilians. Among the taxa described from the latest Cretaceous of Europe, the genus Allodaposuchus is one of the most common but also one of the most controversial. However, because of its fragmentary record, several issues regarding its phylogenetic emplacement and its ecology remain unsolved or unknown. The discovery of a single specimen attributed to Allodaposuchus, represented by both cranial and postcranial remains, from the Casa Fabà site (Tremp Basin, NE Spain) in the lower red unit of the Tremp Fm. (early Maastrichtian, Late Cretaceous) offers a unique opportunity to deepen in the phylogenetic relationships of the group and its ecological features. Methods. The specimen is described in detail, and CT scan of the skull is performed in order to study the endocranial morphology as well as paratympanic sinuses configuration. In addition, myological and phylogenetic analyses are also carried out on the specimen for to shed light in ecological and phylogenetic issues, respectively. Results. The specimen described herein represents a new species, Allodaposuchus hulki sp. nov., closely related to the Romanian A. precedens. The CT scan of the skull revealed an unexpected paratympanic sinuses configuration. Allosaposuchus hulki exhibits an “anterodorsal tympanic sinus” not observed in any other extant or extinct crocodilian. The caudal tympanic recesses are extremely enlarged, and the expanded quadratic sinus seems to be connected to the middle-ear channel. Phylogenetic analyses confirm the emplacement of the informal taxonomic group ‘Allodaposuchia’ at the base of Crocodylia, being considered the sister group of Borealosuchus and Planocraniidae. Discussion. Although this is a preliminary hypothesis, the unique paratympanic configuration displayed by A. hulki suggests that it could possess a high-specialized auditory system. Further, the large cranial cavities could help to reduce the weight of the cranium. Concerning the postcranial skeleton, Allodaposuchus hulki shows massive and robust vertebrae and forelimb bones, suggesting it could have a bulky body. The myological study performed on the anterior limb elements supports this interpretation. In addition, several bone and muscular features seem to point at a semi-erected position of the forelimbs during terrestrial locomotion. Taking all the above results into consideration, it seems plausible to suggest that A. hulki could conduct large incursions out of the water and have a semi-terrestrial lifestyle.
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Affiliation(s)
- Alejandro Blanco
- Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona , Sabadell, Catalonia , Spain
| | - Josep Fortuny
- Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona , Sabadell, Catalonia , Spain
| | - Alba Vicente
- Departament d'Estratigrafia, Paleontologia i Geociències marines, Facultat de Geologia, Universitat de Barcelona, Carrer de Martí i Franquès s/n , Barcelona, Catalonia , Spain
| | - Àngel H Luján
- Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona , Sabadell, Catalonia , Spain
| | - Jordi Alexis García-Marçà
- Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona , Sabadell, Catalonia , Spain
| | - Albert G Sellés
- Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona , Sabadell, Catalonia , Spain
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33
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Bierman HS, Carr CE. Sound localization in the alligator. Hear Res 2015; 329:11-20. [PMID: 26048335 DOI: 10.1016/j.heares.2015.05.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 05/12/2015] [Accepted: 05/24/2015] [Indexed: 10/23/2022]
Abstract
In early tetrapods, it is assumed that the tympana were acoustically coupled through the pharynx and therefore inherently directional, acting as pressure difference receivers. The later closure of the middle ear cavity in turtles, archosaurs, and mammals is a derived condition, and would have changed the ear by decoupling the tympana. Isolation of the middle ears would then have led to selection for structural and neural strategies to compute sound source localization in both archosaurs and mammalian ancestors. In the archosaurs (birds and crocodilians) the presence of air spaces in the skull provided connections between the ears that have been exploited to improve directional hearing, while neural circuits mediating sound localization are well developed. In this review, we will focus primarily on directional hearing in crocodilians, where vocalization and sound localization are thought to be ecologically important, and indicate important issues still awaiting resolution.
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Affiliation(s)
- Hilary S Bierman
- Center for Comparative and Evolutionary Biology of Hearing, Department of Biology, University of Maryland College Park, College Park, Maryland 20742, USA.
| | - Catherine E Carr
- Center for Comparative and Evolutionary Biology of Hearing, Department of Biology, University of Maryland College Park, College Park, Maryland 20742, USA.
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Lakes-Harlan R, Scherberich J. Position-dependent hearing in three species of bushcrickets (Tettigoniidae, Orthoptera). ROYAL SOCIETY OPEN SCIENCE 2015; 2:140473. [PMID: 26543574 PMCID: PMC4632538 DOI: 10.1098/rsos.140473] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 05/14/2015] [Indexed: 06/05/2023]
Abstract
A primary task of auditory systems is the localization of sound sources in space. Sound source localization in azimuth is usually based on temporal or intensity differences of sounds between the bilaterally arranged ears. In mammals, localization in elevation is possible by transfer functions at the ear, especially the pinnae. Although insects are able to locate sound sources, little attention is given to the mechanisms of acoustic orientation to elevated positions. Here we comparatively analyse the peripheral hearing thresholds of three species of bushcrickets in respect to sound source positions in space. The hearing thresholds across frequencies depend on the location of a sound source in the three-dimensional hearing space in front of the animal. Thresholds differ for different azimuthal positions and for different positions in elevation. This position-dependent frequency tuning is species specific. Largest differences in thresholds between positions are found in Ancylecha fenestrata. Correspondingly, A. fenestrata has a rather complex ear morphology including cuticular folds covering the anterior tympanal membrane. The position-dependent tuning might contribute to sound source localization in the habitats. Acoustic orientation might be a selective factor for the evolution of morphological structures at the bushcricket ear and, speculatively, even for frequency fractioning in the ear.
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35
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Greene NT, Anbuhl KL, Williams W, Tollin DJ. The acoustical cues to sound location in the guinea pig (Cavia porcellus). Hear Res 2014; 316:1-15. [PMID: 25051197 DOI: 10.1016/j.heares.2014.07.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 07/02/2014] [Accepted: 07/09/2014] [Indexed: 10/25/2022]
Abstract
There are three main acoustical cues to sound location, each attributable to space- and frequency-dependent filtering of the propagating sound waves by the outer ears, head, and torso: Interaural differences in time (ITD) and level (ILD) as well as monaural spectral shape cues. While the guinea pig has been a common model for studying the anatomy, physiology, and behavior of binaural and spatial hearing, extensive measurements of their available acoustical cues are lacking. Here, these cues were determined from directional transfer functions (DTFs), the directional components of the head-related transfer functions, for 11 adult guinea pigs. In the frontal hemisphere, monaural spectral notches were present for frequencies from ∼10 to 20 kHz; in general, the notch frequency increased with increasing sound source elevation and in azimuth toward the contralateral ear. The maximum ITDs calculated from low-pass filtered (2 kHz cutoff frequency) DTFs were ∼250 μs, whereas the maximum ITD measured with low-frequency tone pips was over 320 μs. A spherical head model underestimates ITD magnitude under normal conditions, but closely approximates values when the pinnae were removed. Interaural level differences (ILDs) strongly depended on location and frequency; maximum ILDs were <10 dB for frequencies <4 kHz and were as large as 40 dB for frequencies >10 kHz. Removal of the pinna reduced the depth and sharpness of spectral notches, altered the acoustical axis, and reduced the acoustical gain, ITDs, and ILDs; however, spectral shape features and acoustical gain were not completely eliminated, suggesting a substantial contribution of the head and torso in altering the sounds present at the tympanic membrane.
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Affiliation(s)
- Nathaniel T Greene
- Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Department of Otolaryngology, University of Colorado School of Medicine, 12631 East 17th Avenue, B205, Aurora, CO 80045, USA.
| | - Kelsey L Anbuhl
- Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Neuroscience Training Program, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Whitney Williams
- Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Daniel J Tollin
- Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Neuroscience Training Program, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Department of Otolaryngology, University of Colorado School of Medicine, 12631 East 17th Avenue, B205, Aurora, CO 80045, USA
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36
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Knight K. Canal between ears helps alligators pinpoint sound. J Exp Biol 2014. [DOI: 10.1242/jeb.105239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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