scholarly journals Inner ear sensory system changes as extinct crocodylomorphs transitioned from land to water

2020 ◽  
Vol 117 (19) ◽  
pp. 10422-10428 ◽  
Author(s):  
Julia A. Schwab ◽  
Mark T. Young ◽  
James M. Neenan ◽  
Stig A. Walsh ◽  
Lawrence M. Witmer ◽  
...  
Keyword(s):  
Inner Ear ◽  
Vestibular System ◽  
Sensory System ◽  
Evolutionary Trend ◽  
Postcranial Skeleton ◽  
Evolutionary Transitions ◽  
Marine Reptiles ◽  
History Of ◽  
Type Of Transition ◽  
New Habitats

Major evolutionary transitions, in which animals develop new body plans and adapt to dramatically new habitats and lifestyles, have punctuated the history of life. The origin of cetaceans from land-living mammals is among the most famous of these events. Much earlier, during the Mesozoic Era, many reptile groups also moved from land to water, but these transitions are more poorly understood. We use computed tomography to study changes in the inner ear vestibular system, involved in sensing balance and equilibrium, as one of these groups, extinct crocodile relatives called thalattosuchians, transitioned from terrestrial ancestors into pelagic (open ocean) swimmers. We find that the morphology of the vestibular system corresponds to habitat, with pelagic thalattosuchians exhibiting a more compact labyrinth with wider semicircular canal diameters and an enlarged vestibule, reminiscent of modified and miniaturized labyrinths of other marine reptiles and cetaceans. Pelagic thalattosuchians with modified inner ears were the culmination of an evolutionary trend with a long semiaquatic phase, and their pelagic vestibular systems appeared after the first changes to the postcranial skeleton that enhanced their ability to swim. This is strikingly different from cetaceans, which miniaturized their labyrinths soon after entering the water, without a prolonged semiaquatic stage. Thus, thalattosuchians and cetaceans became secondarily aquatic in different ways and at different paces, showing that there are different routes for the same type of transition.

scholarly journals Neurophysiology goes wild: from exploring sensory coding in sound proof rooms to natural environments

2021 ◽  
Vol 207 (3) ◽  
pp. 303-319
Author(s):  
Heiner Römer
Keyword(s):  
Sensory System ◽  
Sensory Systems ◽  
Natural Environments ◽  
Sensory Coding ◽  
Noise Levels ◽  
Sensory Physiology ◽  
Sound Localisation ◽  
Physical Environments ◽  
History Of ◽  
Adaptive Behaviours

AbstractTo perform adaptive behaviours, animals have to establish a representation of the physical “outside” world. How these representations are created by sensory systems is a central issue in sensory physiology. This review addresses the history of experimental approaches toward ideas about sensory coding, using the relatively simple auditory system of acoustic insects. I will discuss the empirical evidence in support of Barlow’s “efficient coding hypothesis”, which argues that the coding properties of neurons undergo specific adaptations that allow insects to detect biologically important acoustic stimuli. This hypothesis opposes the view that the sensory systems of receivers are biased as a result of their phylogeny, which finally determine whether a sound stimulus elicits a behavioural response. Acoustic signals are often transmitted over considerable distances in complex physical environments with high noise levels, resulting in degradation of the temporal pattern of stimuli, unpredictable attenuation, reduced signal-to-noise levels, and degradation of cues used for sound localisation. Thus, a more naturalistic view of sensory coding must be taken, since the signals as broadcast by signallers are rarely equivalent to the effective stimuli encoded by the sensory system of receivers. The consequences of the environmental conditions for sensory coding are discussed.

scholarly journals Biomechanical Study of the Vestibular System of the Inner Ear Using a Numerical Method

2017 ◽  
Vol 24 ◽  
pp. 30-37 ◽  
Author(s):  
Carla F. Santos ◽  
Jorge Belinha ◽  
Fernanda Gentil ◽  
Marco Parente ◽  
Bruno Areias ◽  
...  
Keyword(s):  
Numerical Method ◽  
Inner Ear ◽  
Vestibular System ◽  
Biomechanical Study

scholarly journals Evolution of Endolymph Secretion and Endolymphatic Potential Generation in the Vertebrate Inner Ear

2018 ◽  
Vol 92 (1-2) ◽  
pp. 1-31 ◽  
Author(s):  
Christine Köppl ◽  
Viviane Wilms ◽  
Ian John Russell ◽  
Hans Gerd Nothwang
Keyword(s):  
Inner Ear ◽  
Lateral Line ◽  
Vestibular System ◽  
Molecular Mechanisms ◽  
Receptor Potential ◽  
Cell Types ◽  
Cell Receptor ◽  
Striking Difference ◽  
High K ◽  
Endolymphatic Potential

The ear of extant vertebrates reflects multiple independent evolutionary trajectories. Examples include the middle ear or the unique specializations of the mammalian cochlea. Another striking difference between vertebrate inner ears concerns the differences in the magnitude of the endolymphatic potential. This differs both between the vestibular and auditory part of the inner ear as well as between the auditory periphery in different vertebrates. Here we provide a comparison of the cellular and molecular mechanisms in different endorgans across vertebrates. We begin with the lateral line and vestibular systems, as they likely represent plesiomorphic conditions, then review the situation in different vertebrate auditory endorgans. All three systems harbor hair cells bathed in a high (K+) environment. Superficial lateral line neuromasts are bathed in an electrogenically maintained high (K+) microenvironment provided by the complex gelatinous cupula. This is associated with a positive endocupular potential. Whether this is a special or a universal feature of lateral line and possibly vestibular cupulae remains to be discovered. The vestibular system represents a closed system with an endolymph that is characterized by an enhanced (K+) relative to the perilymph. Yet only in land vertebrates does (K+) exceed (Na+). The endolymphatic potential ranges from +1 to +11 mV, albeit we note intriguing reports of substantially higher potentials of up to +70 mV in the cupula of ampullae of the semicircular canals. Similarly, in the auditory system, a high (K+) is observed. However, in contrast to the vestibular system, the positive endolymphatic potential varies more substantially between vertebrates, ranging from near zero mV to approximately +100 mV. The tissues generating endolymph in the inner ear show considerable differences in cell types and location. So-called dark cells and the possibly homologous ionocytes in fish appear to be the common elements, but there is always at least one additional cell type present. To inspire research in this field, we propose a classification for these cell types and discuss potential evolutionary relationships. Their molecular repertoire is largely unknown and provides further fertile ground for future investigation. Finally, we propose that the ultimate selective pressure for an increased endolymphatic potential, as observed in mammals and to a lesser extent in birds, is specifically to maintain the AC component of the hair-cell receptor potential at high frequencies. In summary, we identify intriguing questions for future directions of research into the molecular and cellular basis of the endolymph in the different compartments of the inner ear. The answers will provide important insights into evolutionary and developmental processes in a sensory organ essential to many species, including humans.

scholarly journals Conflict and cooperation in eukaryogenesis: implications for the timing of endosymbiosis and the evolution of sex

2015 ◽  
Author(s):  
Arunas L Radzvilavicius ◽  
Neil W Blackstone
Keyword(s):  
Cell Fusion ◽  
Mitochondrial Gene ◽  
Evolutionary Process ◽  
Eukaryotic Cell ◽  
Evolutionary Transition ◽  
Evolutionary Transitions ◽  
Conflict And Cooperation ◽  
Conflict Mediation ◽  
Considerable Debate ◽  
History Of

The complex eukaryotic cell is a result of an ancient endosymbiosis and one of the major evolutionary transitions. The timing of key eukaryotic innovations relative to the acquisition of mitochondria remains subject to considerable debate, yet the evolutionary process itself might constrain the order of these events. Endosymbiosis entailed levels-of-selection conflicts, and mechanisms of conflict mediation had to evolve for eukaryogenesis to proceed. The initial mechanisms of conflict mediation were based on the pathways inherited from prokaryotic symbionts and led to metabolic homeostasis in the eukaryotic cell, while later mechanisms (e.g., mitochondrial gene transfer) contributed to the expansion of the eukaryotic genome. Perhaps the greatest opportunity for conflict arose with the emergence of sex involving whole-cell fusion. While early evolution of cell fusion may have affected symbiont acquisition, sex together with the competitive symbiont behaviour would have destabilised the emerging higher-level unit. Cytoplasmic mixing, on the other hand, would have been beneficial for selfish endosymbionts, capable of using their own metabolism to manipulate the life history of the host. Given the results of our mathematical modelling, we argue that sex represents a rather late proto- eukaryotic innovation, allowing for the growth of the chimeric nucleus and contributing to the successful completion of the evolutionary transition.

scholarly journals The order of trait emergence in the evolution of cyanobacterial multicellularity

2019 ◽  
Author(s):  
Katrin Hammerschmidt ◽  
Giddy Landan ◽  
Fernando Domingues Kümmel Tria ◽  
Jaime Alcorta ◽  
Tal Dagan
Keyword(s):  
Division Of Labor ◽  
Phenotypic Trait ◽  
Evolutionary Transition ◽  
Evolutionary Transitions ◽  
Differentiated Cells ◽  
Labor Theory ◽  
Significant Events ◽  
Reproductive Life ◽  
History Of ◽  
Multicellular Organisms

AbstractThe transition from unicellular to multicellular organisms is one of the most significant events in the history of life. Key to this process is the emergence of Darwinian individuality at the higher level: groups must become single entities capable of reproduction for selection to shape their evolution. Evolutionary transitions in individuality are characterized by cooperation between the lower level entities and by division of labor. Theory suggests that division of labor may drive the transition to multicellularity by eliminating the trade-off between two incompatible processes that cannot be performed simultaneously in one cell. Here we examine the evolution of the most ancient multicellular transition known today, that of cyanobacteria, where we reconstruct the sequence of ecological and phenotypic trait evolution. Our results show that the prime driver of multicellularity in cyanobacteria was the expansion in metabolic capacity offered by nitrogen fixation, which was accompanied by the emergence of the filamentous morphology and succeeded by a reproductive life cycle. This was followed by the progression of multicellularity into higher complexity in the form of differentiated cells and patterned multicellularity.Significance StatementThe emergence of multicellularity is a major evolutionary transition. The oldest transition, that of cyanobacteria, happened more than 3 to 3.5 billion years ago. We find N2 fixation to be the prime driver of multicellularity in cyanobacteria. This innovation faced the challenge of incompatible metabolic processes since the N2 fixing enzyme (nitrogenase) is sensitive to oxygen, which is abundantly found in cyanobacteria cells performing photosynthesis. At the same time, N2-fixation conferred an adaptive benefit to the filamentous morphology as cells could divide their labour into performing either N2-fixation or photosynthesis. This was followed by the culmination of complex multicellularity in the form of differentiated cells and patterned multicellularity.

Dizziness

2021 ◽  
Author(s):  
Kevin A. Kerber ◽  
Robert W. Baloh
Keyword(s):  
Vestibular System ◽  
Clinical Medicine ◽  
Background Information ◽  
History Taking ◽  
Symptom Presentation ◽  
Anatomy And Physiology ◽  
Common Causes ◽  
History Of ◽  
Specific Disorders ◽  
Key Aspects

Dizziness is the quintessential symptom presentation in all of clinical medicine. It is a common reason that patients present to a physician. This chapter provides background information about the vestibular system, then reviews key aspects of history-taking and examination of the patient, then discusses specific disorders and common presentation types. Throughout the chapter the focus is on neurologic and vestibular disorders. Normal vestibular anatomy and physiology are discussed, followed by recommendations for history-taking and the physical examination. Specific disorders that cause dizziness are explored, along with common causes of non-specific dizziness. Common presentations are discussed, including acute severe dizziness, recurrent attacks, and recurrent positional vertigo. Finally, the chapter looks at laboratory investigations in diagnosis and management. Figures include population prevalence of dizziness symptoms, the anatomy of inner structures, primary afferent vestibular nerve activity, the head thrust test, the Dix-Hallpike maneuver, the supine positional test, the canalith repositioning procedure, and the barbecue roll maneuver. Tables list physiologic properties and clinical features of the components of the peripheral vestibular system, information to be acquired from history of the present illness, common symptoms patients report as dizziness, examination components, distinguishing among common peripheral and central vertigo syndromes, common causes of nonspecific dizziness, types of dizziness presentations, relevant imaging abnormalities on neuroimaging studies, vestibular testing components, and medical therapy for symptomatic dizziness. This review contains 8 highly rendered figures, 11 tables, and 69 references.

Dizziness

2021 ◽  
Author(s):  
Kevin A. Kerber ◽  
Robert W. Baloh
Keyword(s):  
Vestibular System ◽  
Clinical Medicine ◽  
Background Information ◽  
History Taking ◽  
Symptom Presentation ◽  
Anatomy And Physiology ◽  
Common Causes ◽  
History Of ◽  
Specific Disorders ◽  
Key Aspects

Dizziness is the quintessential symptom presentation in all of clinical medicine. It is a common reason that patients present to a physician. This chapter provides background information about the vestibular system, then reviews key aspects of history-taking and examination of the patient, then discusses specific disorders and common presentation types. Throughout the chapter the focus is on neurologic and vestibular disorders. Normal vestibular anatomy and physiology are discussed, followed by recommendations for history-taking and the physical examination. Specific disorders that cause dizziness are explored, along with common causes of non-specific dizziness. Common presentations are discussed, including acute severe dizziness, recurrent attacks, and recurrent positional vertigo. Finally, the chapter looks at laboratory investigations in diagnosis and management. Figures include population prevalence of dizziness symptoms, the anatomy of inner structures, primary afferent vestibular nerve activity, the head thrust test, the Dix-Hallpike maneuver, the supine positional test, the canalith repositioning procedure, and the barbecue roll maneuver. Tables list physiologic properties and clinical features of the components of the peripheral vestibular system, information to be acquired from history of the present illness, common symptoms patients report as dizziness, examination components, distinguishing among common peripheral and central vertigo syndromes, common causes of nonspecific dizziness, types of dizziness presentations, relevant imaging abnormalities on neuroimaging studies, vestibular testing components, and medical therapy for symptomatic dizziness. This review contains 8 highly rendered figures, 11 tables, and 69 references.

Developing inner ear sensory neurons require TrkB and TrkC receptors for innervation of their peripheral targets

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3381-3391 ◽  
Author(s):  
T. Schimmang ◽  
L. Minichiello ◽  
E. Vazquez ◽  
I. San Jose ◽  
F. Giraldez ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Catalytic Domain ◽  
Sensory System ◽  
Sensory Epithelium ◽  
Outer Hair Cells ◽  
Developmental Study ◽  
Inner Hair Cells ◽  
Vestibular Neurons ◽  
Cochlear Neurons

The trkB and trkC genes are expressed during the formation of the vestibular and auditory system. To elucidate the function of trkB and trkC during this process, we have analysed mice carrying a germline mutation in the tyrosine kinase catalytic domain of these genes. Neuroanatomical analysis of homozygous mutant mice revealed neuronal deficiencies in the vestibular and cochlear ganglia. In trkB (−/−) animals vestibular neurons and a subset of cochlear neurons responsible for the innervation of outer hair cells were drastically reduced. The peripheral targets of the respective neurons showed severe innervation defects. A comparative analysis of ganglia from trkC (−/−) mutants revealed a moderate reduction of vestibular neurons and a specific loss of cochlear neurons innervating inner hair cells. No nerve fibres were detected in the sensory epithelium containing inner hair cells. A developmental study of trkB (−/−) and trkC (−/−) mice showed that some vestibular and cochlear fibres initially reached their peripheral targets but failed to maintain innervation and degenerated. TrkB and TrkC receptors are therefore required for the survival of specific neuronal populations and the maintenance of target innervation in the peripheral sensory system of the inner ear.

Mutations affecting development of the zebrafish inner ear and lateral line

Development ◽  
1996 ◽  
Vol 123 (1) ◽  
pp. 241-254 ◽  
Author(s):  
T.T. Whitfield ◽  
M. Granato ◽  
F.J. van Eeden ◽  
U. Schach ◽  
M. Brand ◽  
...  
Keyword(s):  
Inner Ear ◽  
Lateral Line ◽  
Large Scale ◽  
Sensory System ◽  
Semicircular Canals ◽  
Abnormal Development ◽  
Pigment Cells ◽  
Otic Vesicle ◽  
In The Wild ◽  
Complementation Groups

Mutations giving rise to anatomical defects in the inner ear have been isolated in a large scale screen for mutations causing visible abnormalities in the zebrafish embryo (Haffter, P., Granato, M., Brand, M. et al. (1996) Development 123, 1–36). 58 mutants have been classified as having a primary ear phenotype; these fall into several phenotypic classes, affecting presence or size of the otoliths, size and shape of the otic vesicle and formation of the semicircular canals, and define at least 20 complementation groups. Mutations in seven genes cause loss of one or both otoliths, but do not appear to affect development of other structures within the ear. Mutations in seven genes affect morphology and patterning of the inner ear epithelium, including formation of the semicircular canals and, in some, development of sensory patches (maculae and cristae). Within this class, dog-eared mutants show abnormal development of semicircular canals and lack cristae within the ear, while in van gogh, semicircular canals fail to form altogether, resulting in a tiny otic vesicle containing a single sensory patch. Both these mutants show defects in the expression of homeobox genes within the otic vesicle. In a further class of mutants, ear size is affected while patterning appears to be relatively normal; mutations in three genes cause expansion of the otic vesicle, while in little ears and microtic, the ear is abnormally small, but still contains all five sensory patches, as in the wild type. Many of the ear and otolith mutants show an expected behavioural phenotype: embryos fail to balance correctly, and may swim on their sides, upside down, or in circles. Several mutants with similar balance defects have also been isolated that have no obvious structural ear defect, but that may include mutants with vestibular dysfunction of the inner ear (Granato, M., van Eeden, F. J. M., Schach, U. et al. (1996) Development, 123, 399–413,). Mutations in 19 genes causing primary defects in other structures also show an ear defect. In particular, ear phenotypes are often found in conjunction with defects of neural crest derivatives (pigment cells and/or cartilaginous elements of the jaw). At least one mutant, dog-eared, shows defects in both the ear and another placodally derived sensory system, the lateral line, while hypersensitive mutants have additional trunk lateral line organs.

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