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Current Biology : CB Oct 2022Birds contribute prominently to the terrestrial soundscapes on Earth. The sounds can arise from different sources, such as drumming by woodpeckers, bill clapping by...
Birds contribute prominently to the terrestrial soundscapes on Earth. The sounds can arise from different sources, such as drumming by woodpeckers, bill clapping by storks or feather vibrations in the courtship flights of snipes and hummingbirds. However, most avian sounds are generated in the avian vocal organ, the syrinx. Vocal behavior is used in many different contexts and features prominently in mate choice and reproduction. It is therefore thought to have played an important role in the remarkable diversification of birds.
Topics: Animals; Vocalization, Animal; Biological Evolution; Birds; Trachea; Feathers
PubMed: 36283372
DOI: 10.1016/j.cub.2022.08.034 -
Proceedings of the National Academy of... Oct 2018In its most basic conception, a novelty is simply something new. However, when many previously proposed evolutionary novelties have been illuminated by genetic,... (Review)
Review
In its most basic conception, a novelty is simply something new. However, when many previously proposed evolutionary novelties have been illuminated by genetic, developmental, and fossil data, they have refined and narrowed our concept of biological "newness." For example, they show that these novelties can occur at one or multiple levels of biological organization. Here, we review the identity of structures in the avian vocal organ, the syrinx, and bring together developmental data on airway patterning, structural data from across tetrapods, and mathematical modeling to assess what is novel. In contrast with laryngeal cartilages that support vocal folds in other vertebrates, we find no evidence that individual cartilage rings anchoring vocal folds in the syrinx have homology with any specific elements in outgroups. Further, unlike all other vertebrate vocal organs, the syrinx is not derived from a known valve precursor, and its origin involves a transition from an evolutionary "spandrel" in the respiratory tract, the site where the trachea meets the bronchi, to a target for novel selective regimes. We find that the syrinx falls into an unusual category of novel structures: those having significant functional overlap with the structures they replace. The syrinx, along with other evolutionary novelties in sensory and signaling modalities, may more commonly involve structural changes that contribute to or modify an existing function rather than those that enable new functions.
Topics: Animals; Biological Evolution; Birds; Fossils; Larynx; Phylogeny; Respiratory System; Trachea; Vocal Cords; Vocalization, Animal
PubMed: 30249637
DOI: 10.1073/pnas.1804586115 -
Bio-protocol Sep 2020Songbirds, such as the zebra finch, are a popular animal model for studying the neural basis of vocal and complex skill learning. Adult male zebra finches produce...
Songbirds, such as the zebra finch, are a popular animal model for studying the neural basis of vocal and complex skill learning. Adult male zebra finches produce courtship song toward females (referred to as 'directed song') and recording and analyzing sounds of directed song along with underlying neural activity is important for investigating behavioral and neural mechanisms of song production and learning. However, recording of directed song is easily contaminated by calls that are often as loud as directed songs and frequently produced by a female bird is presented in the same sound-recording chamber to elicit directed song. We developed a new surgical procedure to relatively easily and almost completely devocalize female zebra finches semi-permanently, without affecting other behaviors. This procedure enables researchers to record directed songs with almost no contamination by female calls. The procedure can also be used to devocalize male birds as well and, thus, has great potential for a variety of experimental purposes, such as long-term elimination of auditory feedback during singing in male birds.
PubMed: 33659411
DOI: 10.21769/BioProtoc.3752 -
BMJ Case Reports Jun 2021The Chiari I malformation (CM-I) is characterised by overcrowding of the posterior fossa and descent of the cerebellar tonsils and is associated with syringomyelia. With... (Review)
Review
The Chiari I malformation (CM-I) is characterised by overcrowding of the posterior fossa and descent of the cerebellar tonsils and is associated with syringomyelia. With the increasing availability of magnetic resonance imaging, CM-I is placing a growing burden on neurosurgical services. However, its natural history remains poorly understood, and the timing and nature of surgical intervention is controversial. We present a case of a significant, symptomatic CM-I with associated syrinx which underwent complete spontaneous resolution over a 4-year period. Spontaneous regression of Chiari malformation and syringomyelia is exceedingly rare; a literature review reveals 15 other cases and only one case which underwent complete resolution. The present case and literature review suggest a more benign natural history of CM-I and support a more conservative approach to its management. Further studies are required to determine whether any factors can predict resolution for certain patient cohorts.
Topics: Arnold-Chiari Malformation; Decompression, Surgical; Humans; Magnetic Resonance Imaging; Syringomyelia; Trachea
PubMed: 34155013
DOI: 10.1136/bcr-2021-241789 -
Journal of Morphology Dec 2011Sexually dimorphic vocal behavior in zebra finches (Taeniopygia guttata) is associated with a 100% larger syrinx in males and other morphological adaptations of the...
Sexually dimorphic vocal behavior in zebra finches (Taeniopygia guttata) is associated with a 100% larger syrinx in males and other morphological adaptations of the sound source. The songbird syrinx consists of two independent sound sources, whose specialization for different spectral ranges may be reflected in morphological properties, but the morphology of labia and syringeal skeleton have not been investigated for lateralized specializations. Similarly, little is known whether the morphology of the songbird vocal tract reflects differences in vocal behavior. Here, we tested the hypothesis that different vocal behavior and specialization is reflected in the morphology. We investigated syringeal and upper vocal tract morphology of male and female European starlings (Sturnus vulgaris). Female starlings exhibit smaller vocal repertoires and sing at lower rates than males. In males, the left syrinx produces mostly low frequencies, while the right one is used for higher notes. Macroscopic and histological techniques were used to record nineteen measurements from the syrinx and the vocal tract which were tested for sexual differences in syrinx and vocal tract and for lateral asymmetry within the syrinx. Sexually dimorphic vocal behavior is reflected in the morphology of the starling syrinx. Males have a larger syrinx with the size difference attributable to increased muscle mass and three enlarged elements of the syringeal skeleton. The upper vocal tract, however, does not differ between males and females. Distinct lateralization was found in two elements of the syringeal skeleton of females, and the labia in the left syrinx are larger than those on the right in both sexes. The sexual dimorphism of the syringeal size is smaller in starlings (35%) than in zebra finches (100%), which is consistent with the different vocal behavior of females in both species. The morphological differences between the two sound sources are discussed in relation to their vocal performance.
Topics: Animals; Female; Male; Organ Size; Sex Factors; Starlings; Trachea; Vocalization, Animal
PubMed: 22076959
DOI: 10.1002/jmor.11007 -
Journal of Physiology, Paris Jun 2013One major feature of the remarkable vocal repertoires of birds is the range of fundamental frequencies across species, but also within individual species. This review... (Review)
Review
One major feature of the remarkable vocal repertoires of birds is the range of fundamental frequencies across species, but also within individual species. This review discusses four variables that determine the oscillation frequency of the vibrating structures within a bird's syrinx. These are (1) viscoelastic properties of the oscillating tissue, (2) air sac pressure, (3) neuromuscular control of movements and (4) source-filter interactions. Our current understanding of morphology, biomechanics and neural control suggests that a complex interplay of these parameters can lead to multiple combinations for generating a particular fundamental frequency. An increase in the complexity of syringeal morphology from non-passeriform birds to oscines also led to a different interplay for regulating oscillation frequency by enabling control of tension that is partially independent of regulation of airflow. In addition to reviewing the available data for all different contributing variables, we point out open questions and possible approaches.
Topics: Air Sacs; Animals; Birds; Laryngeal Muscles; Respiration; Sound Spectrography; Trachea; Vocalization, Animal
PubMed: 23238240
DOI: 10.1016/j.jphysparis.2012.11.001 -
Veterinary Research Forum : An... 2023Syrinx is a voice device and shows structural and functional differences between bird species. This study aimed to investigate morphological and histological structures...
Syrinx is a voice device and shows structural and functional differences between bird species. This study aimed to investigate morphological and histological structures of the syrinx in chukar partridge () and Japanese quail (). In the present study, 12 male chukar partridges and 12 male Japanese quail were used. The syrinx tissues were photographed by digital camera and fixed in formaldehyde solution. Five syrinxes were stained with methylene blue to make the syrinx rings distinct. After anatomical examination, tissues were passed through alcohol series, cleaned in xylene, and embedded in paraffin blocks. The blocks were cut and obtained sections were stained with Crossman modified triple staining and examined under camera attached light microscope. The syrinx of chukar partridges and Japanese quail consisted of cartilaginous tracheasyngeales and bronchosyngeales in the region of and at the level of . The tracheal rings constituting syrinx were counted three in chukar partridge and four in Japanese quail. The bronchial rings comprising syrinx counted nine in chukar partridge and eight in Japanese quail. In the histological examination, the structure was hyaline cartilage and calcificated with increasing ages being covered by pseudostratified columnar epithelium. The results of the study suggested that chukar partridge and Japanese quail syrinxes have some morphological differences compared to the other bird species; but, anatomically and histologically similarities to many bird species.
PubMed: 37383648
DOI: 10.30466/vrf.2022.549823.3408 -
Scientific Reports Feb 2020How sound is generated in the hummingbird syrinx is largely unknown despite their complex vocal behavior. To fill this gap, syrinx anatomy of four North American...
How sound is generated in the hummingbird syrinx is largely unknown despite their complex vocal behavior. To fill this gap, syrinx anatomy of four North American hummingbird species were investigated by histological dissection and contrast-enhanced microCT imaging, as well as measurement of vocalizations in a heliox atmosphere. The placement of the hummingbird syrinx is uniquely located in the neck rather than inside the thorax as in other birds, while the internal structure is bipartite with songbird-like anatomical features, including multiple pairs of intrinsic muscles, a robust tympanum and several accessory cartilages. Lateral labia and medial tympaniform membranes consist of an extracellular matrix containing hyaluronic acid, collagen fibers, but few elastic fibers. Their upper vocal tract, including the trachea, is shorter than predicted for their body size. There are between-species differences in syrinx measurements, despite similar overall morphology. In heliox, fundamental frequency is unchanged while upper-harmonic spectral content decrease in amplitude, indicating that syringeal sounds are produced by airflow-induced labia and membrane vibration. Our findings predict that hummingbirds have fine control of labia and membrane position in the syrinx; adaptations that set them apart from closely related swifts, yet shows convergence in their vocal organs with those of oscines.
Topics: Animals; Biological Evolution; Elastic Tissue; Female; Male; Muscles; Songbirds; Trachea; Vocalization, Animal; X-Ray Microtomography
PubMed: 32029812
DOI: 10.1038/s41598-020-58843-5 -
PLoS Biology Feb 2019The unique avian vocal organ, the syrinx, is located at the caudal end of the trachea. Although a larynx is also present at the opposite end, birds phonate only with the...
The unique avian vocal organ, the syrinx, is located at the caudal end of the trachea. Although a larynx is also present at the opposite end, birds phonate only with the syrinx. Why only birds evolved a novel sound source at this location remains unknown, and hypotheses about its origin are largely untested. Here, we test the hypothesis that the syrinx constitutes a biomechanical advantage for sound production over the larynx with combined theoretical and experimental approaches. We investigated whether the position of a sound source within the respiratory tract affects acoustic features of the vocal output, including fundamental frequency and efficiency of conversion from aerodynamic energy to sound. Theoretical data and measurements in three bird species suggest that sound frequency is influenced by the interaction between sound source and vocal tract. A physical model and a computational simulation also indicate that a sound source in a syringeal position produces sound with greater efficiency. Interestingly, the interactions between sound source and vocal tract differed between species, suggesting that the syringeal sound source is optimized for its position in the respiratory tract. These results provide compelling evidence that strong selective pressures for high vocal efficiency may have been a major driving force in the evolution of the syrinx. The longer trachea of birds compared to other tetrapods made them likely predisposed for the evolution of a syrinx. A long vocal tract downstream from the sound source improves efficiency by facilitating the tuning between fundamental frequency and the first vocal tract resonance.
Topics: Acoustics; Animal Structures; Animals; Biological Evolution; Birds; Computer Simulation; Larynx; Mammals; Models, Biological; Sound; Trachea; Vocalization, Animal
PubMed: 30730882
DOI: 10.1371/journal.pbio.2006507 -
Anatomical Record (Hoboken, N.J. : 2007) Mar 2015The phonation process of vertebrates is influenced by the material characteristics of the participating structures, ranging from molecular to macroscopic dimensions....
The phonation process of vertebrates is influenced by the material characteristics of the participating structures, ranging from molecular to macroscopic dimensions. Good animal models for phonation research are still lacking. Due to easy availability and relatively simple structure, the syrinx of birds might serve as a good animal model for this purpose. Our aim was therefore to determine structural features of the syrinx and obtain insights into its mucus layer characteristics. Epithelium and glands were analyzed using histological, histochemical, and immunohistochemical methods and conclusions were drawn on the use of the syrinx as a model for phonation research by comparing the epithelium and its mucus characteristics to human laryngeal secretions. Ten adult partridges were analyzed. The tympanum of the syrinx developed from the last two tracheal cartilages, whereas the caudal part of the syrinx was formed from eight pieces of bronchial cartilages. The tracheal and bronchial epithelia and the pessulus of the syrinx were lined by pseudo-stratified columnar epithelium in which goblet cells and intraepithelial glands were localized. Collagen fibers were distributed in the lamina propria of all parts of the syringeal mucosa. Elastic fibers in the membranes of the syrinx showed evident distribution. All glandular epithelial cells and goblet cells were positive for neutral, acidic and carboxylated mucins were dominant in particular. Epithelium and glands revealed positive reactivity with antibodies to the mucins MUC1, MUC2, and MUC5AC. Of these, MUC2 and MUC5AC were dominant. The syrinx of partridge can serve as a good ex vivo model for phonation research.
Topics: Animals; Female; Galliformes; Immunohistochemistry; Male; Models, Animal; Phonation; Respiratory System
PubMed: 25178267
DOI: 10.1002/ar.23044