6. The amphibians’ world

Author(s):  
T. S. Kemp

‘The amphibians’ world’ focuses on the amphibians’ sense organs. Amphibians have the eyes, ears, olfactory organs of smell in the nose, and touch receptors common to all vertebrates, but the relative importance of the different senses varies from group to group depending on habitats and modes of life. Anurans have a sensory world most like that of humans; their vision is good, and includes the ability to see colours, and their hearing is acute. Urodeles and caecilians rely much more on their senses of smell and touch. Amphibian larvae have an additional sensory system called the lateral line system. Amphibians use several sensory cues in combination to navigate around their territories.

For a long time after their discovery in the seventeenth century the lateral-line canals of fishes were considered to be mucus-secreting organs. In 1850 Leydig described sense organs in the lateral-line canals, and this discovery stimulated a keen interest in the investigation of both the morphological and functional features of the lateral-line system. Morphological studies have yielded a thorough understanding of the structure of these organs (Ewart and Mitchell 1892; Cole 1896; Johnson 1917; von Woellwarth 1933). Physiological studies, though numerous, have been less fruitful. An account of the older work was given by Baglioni (1913), and the more recent work is reviewed by Dykgraaf (1933). The only technique until recently available has been the elimination of the sensory system by nerve section and cauterization, and the comparison of the behaviour of intact and operated fishes in response to various stimuli. With so diffuse a structure as the lateral-line system, receiving its nerve supply from the fifth, seventh, ninth and tenth cranial nerves, this method is particularly inadequate, and involves a violent mutilation of the animal. When one considers the crudity of many of these operations, it is not the uncertainty of the results which is remarkable, but rather that some of the conclusions reached should remain valid to-day in the light of far more penetrating experimental analysis. This method of organ elimination could yield at best only an indication of the kind of stimulus that is effective in evoking the excitation of lateral-line receptors. In current textbooks the conclusion of Parker (1904) that the effective stimulus for the lateral line is low-frequency vibration, and that of Hofer (1907) that it is movement of water (i. e. local currents) have received most notice. The observations of Dykgraaf (1933), who employed the more refined methods of von Frisch’s futterdressur technique, support Hofer’s conclusion, and to some extent also Parker’s. Dykgraaf considers the lateral-line system to be an organ of Ferntastsinn , and if this is taken to mean a mechanoreceptor of such sensitivity that it can function both as a touch organ and as a receptor for disturbances coming from a distance, it is undoubtedly a true description, for it is fully confirmed by the direct electrophysiological studies of Hoagland (1933 a, b, c and d ) and of Schriever (1935). The latter, apparently unacquainted with Hoagland’s work, did little more than to confirm several of his observations.


Zoomorphology ◽  
2020 ◽  
Author(s):  
Harald Ahnelt ◽  
David Ramler ◽  
Maria Ø. Madsen ◽  
Lasse F. Jensen ◽  
Sonja Windhager

AbstractThe mechanosensory lateral line of fishes is a flow sensing system and supports a number of behaviors, e.g. prey detection, schooling or position holding in water currents. Differences in the neuromast pattern of this sensory system reflect adaptation to divergent ecological constraints. The threespine stickleback, Gasterosteus aculeatus, is known for its ecological plasticity resulting in three major ecotypes, a marine type, a migrating anadromous type and a resident freshwater type. We provide the first comparative study of the pattern of the head lateral line system of North Sea populations representing these three ecotypes including a brackish spawning population. We found no distinct difference in the pattern of the head lateral line system between the three ecotypes but significant differences in neuromast numbers. The anadromous and the brackish populations had distinctly less neuromasts than their freshwater and marine conspecifics. This difference in neuromast number between marine and anadromous threespine stickleback points to differences in swimming behavior. We also found sexual dimorphism in neuromast number with males having more neuromasts than females in the anadromous, brackish and the freshwater populations. But no such dimorphism occurred in the marine population. Our results suggest that the head lateral line of the three ecotypes is under divergent hydrodynamic constraints. Additionally, sexual dimorphism points to divergent niche partitioning of males and females in the anadromous and freshwater but not in the marine populations. Our findings imply careful sampling as an important prerequisite to discern especially between anadromous and marine threespine sticklebacks.


2017 ◽  
Vol 51 (5) ◽  
pp. 103-115 ◽  
Author(s):  
Kevin Nelson ◽  
Kamran Mohseni

AbstractThis paper presents a sensory system that is biologically inspired by the lateral line sensory system found in fish. This artificial lateral line system provides sensory information to be used in vehicle control algorithms, both to reduce model complexity and to measure hydrodynamic disturbances. The system presented in this paper is a modular implementation that can fit around a vehicle without requiring modifications to the hull. The design and manufacturing processes are presented in detail along with considerations for sensor placement and port spacing. An algorithm for calculating the hydrodynamic forces acting on the surface of a vehicle is derived and experimentally validated. An underwater motion capture system and strain sensors are used to calculate a reference hydrodynamic force that compares favorably with the hydrodynamic force calculated by the lateral line system.


The recognition of the morphological and developmental relationship of the vertebrate auditory organ and the lateral-line system of fishes and aquatic Amphibia rests on the foundation of a large volume of com­ parative researches. The main outlines of this generalization were already laid down forty years ago, and Cole’s work on the cranial nerves and lateral sense organs of fishes (1898) contains a comprehensive treatment of the history of the subject. The acustico-lateral or neuromast system embraces, in addition to the labyrinth and the lateral-line canals, the pit organs found to a greater or less extent in most fishes, the vesicles of Torpedo , and the ampullary canal system of Selachians and Holocephali. Concerning these Cole wrote: “The history of our knowledge of the phylogeny of the sensory canals is coincident with three discoveries—the discovery that the‘mucus’ canals contain sense organs, the discovery of Savi’s vesicles, and the dis­covery of the ampullae of Lorenzini.... We now know that all three types belong to the lateral line system, and I shall suggest that they represent three stages in the development of a canal—the most superficial condition, represented by the pit organs and Savi’s vesicles; the full development, represented by the canal; and the intermediate type, forming neither a Savi vesicle nor yet a canal, represented by the ampullae of Lorenzini” (p. 187). This conception has remained valid to the present day. The ampullae of Lorenzini, with which I am here principally concerned, are briefly described in current text-books as transitional or specialized neuromasts, and the implication always is that structurally and functionally they do not differ significantly from the neuromasts of the lateral-line canals. For example, in their recent exhaustive treatise on the vertebrate nervous system Kappers, Huber and Crosby (1936) state with reference to the lateral-line canals, the Savi vesicles and the ampullae of Lorenzini: “thus in the various animals there is a transition between an open and a closed system for perceiving vibrations" (p. 438).


2012 ◽  
Vol 107 (10) ◽  
pp. 2581-2593 ◽  
Author(s):  
Julie Goulet ◽  
J. Leo van Hemmen ◽  
Sarah N. Jung ◽  
Boris P. Chagnaud ◽  
Björn Scholze ◽  
...  

Fish and aquatic frogs detect minute water motion by means of a specialized mechanosensory system, the lateral line. Ubiquitous in fish, the lateral-line system is characterized by hair-cell based sensory structures across the fish's surface called neuromasts. These neuromasts occur free-standing on the skin as superficial neuromasts (SN) or are recessed into canals as canal neuromasts. SNs respond to rapid changes of water velocity in a small layer of fluid around the fish, including the so-called boundary layer. Although omnipresent, the boundary layer's impact on the SN response is still a matter of debate. For the first time using an information-theoretic approach to this sensory system, we have investigated the SN afferents encoding capabilities. Combining covariance analysis, phase analysis, and modeling of recorded neuronal responses of primary lateral line afferents, we show that encoding by the SNs is adequately described as a linear, velocity-responsive mechanism. Afferent responses display a bimodal distribution of opposite Wiener kernels that likely reflected the two hair-cell populations within a given neuromast. Using frozen noise stimuli, we further demonstrate that SN afferents respond in an extremely precise manner and with high reproducibility across a broad frequency band (10–150 Hz), revealing that an optimal decoder would need to rely extensively on a temporal code. This was further substantiated by means of signal reconstruction of spike trains that were time shifted with respect to their original. On average, a time shift of 3.5 ms was enough to diminish the encoding capabilities of primary afferents by 70%. Our results further demonstrate that the SNs' encoding capability is linearly related to the stimulus outside the boundary layer, and that the boundary layer can, therefore, be neglected while interpreting lateral line response of SN afferents to hydrodynamic stimuli.


2002 ◽  
Vol 88 (3) ◽  
pp. 1252-1262 ◽  
Author(s):  
Matthew S. Weeg ◽  
Andrew H. Bass

The mechanosensory lateral line of fish is a hair cell based sensory system that detects water motion using canal and superficial neuromasts. The trunk lateral line of the plainfin midshipman fish, Porichthys notatus, only has superficial neuromasts. The posterior lateral line nerve (PLLn) therefore innervates trunk superficial neuromasts exclusively and provides the opportunity to investigate the physiological responses of these receptors without the confounding influence of canal organs. We recorded single-unit activity from PLLn primary afferents in response to a vibrating sphere stimulus calibrated to produce an equal velocity across frequencies. Threshold tuning, isovelocity, and input/output curves were constructed using spike rate and vector strength, a measure of phase locking of spike times to the stimulus waveform. All units responded maximally to frequencies of 20–50 Hz. Units were classified as low-pass, band-pass, broadly tuned, or complex based on the shapes of tuning and isovelocity curves between 20 and 100 Hz. A 100 Hz stimulus caused an increase in spike rate in almost 50%, and significant synchronization in >80%, of all units. Midshipman vocalizations contain significant energy at and below 100 Hz, so these results demonstrate that the midshipman peripheral lateral line system can encode these acoustic signals. These results provide the first direct demonstration that units innervating superficial neuromasts in a teleost fish have heterogeneous frequency response properties, including an upper range of sensitivity that overlaps spectral peaks of behaviorally relevant acoustic stimuli.


Author(s):  
Jennifer D. Liddicoat ◽  
B. L. Roberts

The sense organs of the lateral-line system of lower aquatic vertebrates are mechanoreceptors which respond to water movements. They are distributed over the body, usually in lines which form a definite pattern on the head and along each side of the trunk. In the Cyclostomes the sense organs project from the body surface ('free neuromasts'); in other aquatic vertebrates they are usually housed in canals which are sunk into the dermis and which open at regular intervals to the exterior, although in some teleosts and in all modern amphibia the canal system has been secondarily lost and the neuromasts are once again situated externally.


1933 ◽  
Vol 16 (4) ◽  
pp. 715-732 ◽  
Author(s):  
Hudson Hoagland

1. The lateral-line nerves of trout as well as those of catfish are found to discharge impulses spontaneously at a high frequency. 2. The frequency of nerve impulse discharge is measured as a function of the number of participating receptor groups (lateral-line sense organs). A quantitative analysis is made of the contribution to the total response made by each group of sense organs. 3. An analysis of the variability of the response is presented which makes it possible to estimate quantitatively the longitudinal extent of damage to the neuromasts due to surgical manipulation. 4. A method is described for recording the response of a single nerve fiber in the lateral-line trunk. 5. The frequency of the spontaneous discharge from the lateral-line nerve trunk when plotted as a function of temperature according to the Arrhenius equation yields a temperature characteristic of approximately 5000 calories. 6. The variability of the frequency of response as a function of temperature indicates the existence of temperature thresholds for the spontaneous activity of the neuromasts. 7. A possible basis for the spontaneous activity is considered. It is pointed out that the lateral-line system may serve as a model of the Purkinje cells of the cerebellum.


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