Lateral Line Sense Organs Research Articles

Lateral line sensory organs

Lateral line sensory organs

Mechanical factors in the excitation of clupeid lateral lines.

The excitation of lateral line sense organs (neuromasts) might be expected to depend on differences of movement between the liquid inside the main lateral line canals (the ones that contain the neuromasts) and the walls of these canals. We have investigated this net movement in relation to events in the water around fish. Liquid displacements inside a given part of a main lateral line canal of the sprat ( Sprattus sprattus (L.)) are, at any one frequency, linearly related to those in the medium (sea water) adjacent to this part. For the parts of the canal system studied, and below about 80 Hz, the ratio of displacement inside the canal to that in the medium falls with frequency, i. e. the displacement inside the canal follows the velocity in the medium. Sea water displacements in a given length of a main lateral line canal system are proportional to the component of the external velocity that is parallel to the canal. For this component the ratio of displacements inside and outside the lateral line approaches unity at around 80 Hz. The behaviour of a lateral line canal is close to that of a straight capillary tube of roughly the same cross sectional area. Displacements in the canal are advanced in phase relative to those in the external medium and these phase advances are a little larger than those found in capillaries. There is very little mechanical coupling between neighbouring parts of the main canals. Since the cupulae of the neuromasts of the sprat lateral line are driven by frictional forces, the stimulus to a neuromast will (below 80 Hz) be proportional to the acceleration of the medium adjacent to the lateral line. Sprats and fish of three other species ( Clupea harengus L., Hyperoplus lanceolatus (Lesauvage), and Trachurus trachurus (L.) have been shown, when suspended in sound fields emitted by pulsating and vibrating sources, to behave longitudinally as rigid bodies. Under many conditions it proved possible to calculate the longitudinal movements of fish from the differences of pressure between snout and tail. From these two kinds of result we have calculated for a variety of positions in fields around vibrating bodies the motion of a fish and the motion of the liquid in the canals and so estimated the effective stimulus to different parts of the lateral line system. When such calculations were made for a vibrating source of the dimensions of a sprat tail, and for distances comparable to the inter-fish distance within a school, we found that the patterns of net velocities at different neuromasts change dramatically with the position or angle of the fish relative to the source. We estimate that the sprat lateral line system excited in this way could detect a neighbouring fish in a school at distances of up to a few fish lengths. The sprat lateral line sensory system is well suited to giving sensory information in such activities as schooling.

A cobalt study of medullary sensory projections from lateral line nerves, associated cutaneous nerves, and the VIIIth nerve in adult Xenopus

The medullary projections of the anterior lateral line nerve, dorsal branch (Alln.d), the posterior lateral line nerve, dorsal branch (PLLn.d), associated cutaneous nerves, and the VIIIth nerve in Xenopus laevis have been delineated by axonal infusion of cobalt chloride and silver intensification. The peripheral innervation of the posterior lateral line sense organs has also been traced. From wholemount and sectioned preparations, we describe three central projections, extending the length of the ipsilateral medulla but occupying distinct zones: lateral line afferents dorsomedially, stato-acoustic dorsolaterally, and cutaneous ventrolaterally. Arborizations of ALLn.d and PLLn.d afferents are morphologically similar, intermingling throughout the lateral line lobe. Each divides into ascending and descending limbs bearing collaterals, which terminate in the lateral line neuropile and nucleus. Evidence is presented for directional and positional mapping in the branching of individual PLLn.d afferents and for topography in the ALLn.d projection. Second-order neurones have been identified by transneuronal staining and their axons traced into the contralateral torus semicircularis. The morphology of efferent neurones is also described. Rostral branches of PLLn.d also contain cutaneous afferents which run through the medulla into the spinal cord, similar to the nerve V (cutaneous) projection. In nerve VIII preparations, the projection to the compact cochlear nucleus and the massive vestibular projection are identified. Cutaneous and vestibular but not lateral line afferents extend into the cerebellum. The separation of VIIIth nerve and lateral line afferents in Xenopus medulla is considered as evidence against the validity of the acousticolateralis concept. Information processing in the lateral line lobe is discussed in relation to connectivity patterns between first- and second-order neurones.

Structure-related effects of pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis

The effects of seven different pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis, were investigated by means of electrophysiological methods. The results show that two classes of pyrethroid can be clearly distinguished. (i) Pyrethroids without an α-cyano group (permethrin, cismethrin, and bioresmethrin). These noncyano pyrethroids induce short trains of nerve impulses in the lateral-line sense organ. In peripheral nerve branches they induce a depolarizing afterpotential and repetitive firing. These effects are very similar to those previously reported for allethrin. (ii) Pyrethroids with an α-cyano-3-phenoxybenzyl alcohol (cypermethrin, fenpropathrin, deltamethrin, and fenvalerate). In the lateral-line sense organ these α-cyano pyrethroids induce very long trains of nerve impulses which may last for seconds and may contain hundreds or even thousands of impulses. The α-cyano compounds do not cause repetitive activity in peripheral nerves. Instead they induce a quickly reversible, stimulus frequency-dependent suppression of the action potential. Since the chemical structure of cypermethrin differs from that of permethrin only in the α-cyano group and because all four α-cyano compounds act in a very similar way, it is concluded that the α-cyano substituent is responsible for the large differences in neurotoxic effects. In the lateral-line sense organ the duration of nerve impulse trains induced by the noncyano as well as the α-cyano pyrethroids increases dramatically when the temperature is lowered. Further, in sensory fibers the effects of both classes of pyrethroid on the nerve action potential are more pronounced compared to their effects on motor fibers. It is argued that the different neurotoxic effects reported here originate from a common mechanism of action of pyrethroids, which is a prolongation of the transient increase of sodium permeability of the nerve membrane associated with excitation. It is concluded that the sodium channel in the nerve membrane is the major target site of noncyano and α-cyano pyrethroids.

Similar mode of action of pyrethroids and DDT on sodium channel gating in myelinated nerves.

Synthetic pyrethroids are a new class of highly active insecticides with great potential for practical application1. They are generally recognized as neurotoxicants that act directly on excitable membranes2,3. Previous studies have shown that the effect of the pyrethroid allethrin closely resembles that of the classical insecticide dichlorodiphenyl trichloroethane (DDT) in the peripheral nervous system of Xenopus laevis4,5. Both compounds induce intense repetitive activity in sense organs and in myelinated nerve fibres. In the lateral-line sense organ this repetitive activity increases with cooling, a phenomenon that may be related to the negative temperature coefficient of toxicity of DDT6 and pyrethroids7 in insects. In frog node of Ranvier, DDT slows the closing of sodium channels that open during depolarization8,9 so that a prolonged sodium tail current persists after the membrane has been repolarized. We have recently found that the pyrethroid allethrin10 causes a similar sodium tail current in the nodal membrane of Xenopus. Pyrethroids11,12 and DDT13,14 are also known to cause prolongation of the sodium current together with repetitive activity in nerve fibres of invertebrates. The prolonged sodium current is thought to be directly responsible for this repetitive activity3,15, and it has been suggested that the sodium channel in the nerve membrane is the major target site of pyrethroids and DDT-like compounds10,12. We have now investigated the mechanism by which pyrethroids and DDT prolong the sodium current in Xenopus nodal membrane. Our results show that these compounds—despite marked differences in chemical structure—modify sodium channel gating in a strikingly similar way and reduce selectively the rate of closing of the activation gate.

An experimental study on neural crest migration in Barbus conchonius (Cyprinidae, Teleostei), with special reference to the origin of the enteroendocrine cells

A neural crest transplantation technique is described for fish. As in other classes of vertebrates, two pathways of neural crest migration can be distinguished: a lateroventral pathway between somites and ectoderm, and a medioventral pathway between somites and neural tube/notochord. In this paper evidence is presented for a neural crest origin of spinal ganglion cells and pigment cells, and indication for such an origin is obtained for sympathetic and enteric ganglion cells and for cells that are probably homologues to adrenomedullary and paraganglion cells in the future kidney area. The destiny of neural crest cells near the developing lateral-line sense organs is discussed. When grafted into the yolk, neural crest cells or neural tube cells appear to differentiate into 'periblast cells'; this suggests a highly activating influence of the yolk. Many neural crest cells are found around the urinary ducts and, when grafted below the notochord, even within the urinary duct epithelium. These neural crest cells do not invade the gut epithelium, even when grafted adjacent to the developing gut. Consequently enteroendocrine cells in fish are not likely to have a trunk- or rhombencephalic neural crest origin. Another possible origin of these cells will be proposed.

Structural and Functional Organization of the Lateral Line System of Sharks

The lateral line sense organs of sharks include ampullae of Lorenzini and neuromasts. Each of these two classes of receptors is highly specialized and therefore can be expected to biologically respond to one specific modality of stimulus of minimal threshold intensity. Current anatomical, electro-physiological and behavioral evidence indicates that the ampullae are organized to respond to very weak DC and low frequency AC electric fields that originate from external sources in the environment and that this information is used in the detection of prey. Neuromasts consist of canal receptors and pit organs and are mechanoreceptors that are sensitive to water movements caused by external sources as well as the animal's own swimming movements. There is no convincing experimental evidence of the behavioral role that neuromasts play in the life of sharks, but they can orient toward a source that causes water displacements and perhaps use the neuromast system in the coordination of locomotor activity. Ampullae and neuromasts are innervated by different components of the lateral line nerves that project to special terminal areas within the central nervous system. The dorsal root of the anterior lateral line nerve, which is believed to carry nerve fibers from the ampullae of Lorenzini exclusively, enters and terminates within the anterior lateral line lobe of the medulla. Neuromasts (canal and pit organs) are innervated by the ventral root of the anterior lateral line nerve and posterior lateral line nerve, which project to the posterior lateral line lobe (nucleus medialis) of the medulla and, in addition, distribute to the eminentia granularis of the cerebellum, superior and inferior lobes of the auricle, and to the spinal cord. There is no apparent overlap between those central terminal fields that receive fibers from electroreceptors and those that receive fibers from mechanoreceptors nor with the central terminal field of VIIIth nerve neurons. This supports the contention that different functional classes of lateral line receptors are specialized to perform a particular function, but the central coordinating and integrating mechanisms are unknown.

The Topography of the Superficial Roots and Ganglia of the Anterior Lateral Line Nerve of the Smooth Dogfish, Mustelus canis

The topographic relationships of the superficial roots and ganglia of the anterior lateral line nerve (NLLa) to each other and to cranial nerves V, VII and VIII were studied, in the smooth dogfish Mustelus canis, by dissection of Sudan Black B stained specimens. NLLa consists of four branches: namely, superficial ophthalmic, buccal, otic and external mandibular. Each branch carriers lateral line neurons exclusively and forms a dorsal root and a ventral root which enter the anterior lateral line lobe and posterior lateral line lobe of the medulla respectively. It is estimated that slightly more than 50% of the fibers of the superficial ophthalmic, approximately 60% of the fibers of the buccal, at least 35% of the fibers of the otic and about 20% of the fibers of the external mandibular constitute the dorsal root. The ventral root is comprised of less than 50% of the fibers of the superficial ophthalmic, 40% of the fibers of the buccal, at least 50% of the fibers of the otic, and 80% of the fibers of the external mandibular. These results are correlated with the peripheral distribution and central termination of NLLa and it is concluded that the dorsal root carries axons from ampullary receptors and the ventral root carries fibers that innervate ordinary lateral line sense organs.

The ac and dc components in lateral line microphonic potentials.

Measurements of the microphonic potential from the lateral line sensory organs of killifish (Fundulus heteroclitus) are presented in this report. The potential consists of a dc shift and a dominant oscillatory component at twice the frequency of the stimulus, and it grows with the square of the stimulus at low amplitudes. An electrical circuit model of the microphonic is developed, assuming a simple quadratic nonlinearity in the electrical response of an individual hair cell as suggested by Flock. The model allows investigation of variable conductive or variable capacitive effects in microphonic generation, and the results obtained from the model are compared to the observed properties of the microphonic potentials. It is concluded that hair cell microphonics appear to be generated by a process involving current flow through a variable conductance, although capacitive effects of the hair cell are important in determining the waveform of the microphonic and its behavior as a function of frequency. A discrepancy between the observed low-amplitude growth of the microphonic in killifish and the reported low-amplitude growth of the microphonic in other acoustico-lateralis preparations is also discussed. Subject Classification: [43]65.28, [43]65.20, [43]65.40.

Neurotransmitter synthesis in inner ear and lateral line sense organs.

HAIR cells of inner ear sense organs and of lateral line organs in fish are innervated by afferent nerve fibres, to which they transmit information about mechanical stimuli. Efferent inhibitory nerve fibres, which originate in the central nervous system, also innervate most hair cells at their base (Fig. 1b). Recent evidence indicates that both these synapses are chemical; excitatory postsynaptic potentials (e.p.s.p.s) have been recorded in afferent nerve terminals in response to mechanical stimulation1,2 and inhibitory postsynaptic potentials (i.p.s.p.s) have been recorded in hair cells on stimulation of the efferent fibres2. Furthermore, several findings suggest that acetylcholine is the efferent transmitter: i.p.s.p.s in hair cells, as well as the ensuing inhibition of afferent discharge, can be blocked by curare2–5; both acetylcholine esterase and choline acetyltransferase have been found in the efferent fibres6–9. The nature of the afferent transmitter however has not been elucidated, although catecholamines10 and glutamate11 have been implicated.

Unit activity of ganglionic and medullary second order neurones in the eel lateral line system.

AbstractUnitary spike activity has been investigated in the ganglion and the central terminational field of the R. lat. post. N. X. No dorsal root reflex is observed in the intracranial rootlet. There is an excitatory coupling between ganglionic cells in the N. lat. post. which can lead to multiple firing in these cells by stimulation of afferents in the trunk nerve. Second order neurones were identified by their location and variable spike latency to peripheral nerve stimulation. These cells are driven by a large number of active primary afferents from extended parts (order of magnitude 15 cm) of the trunk lateral line. The statistics of spontaneous discharges were studied and compared with that of primary afferent nerve fibres. About 1/3 of secondary neurones are either excited or inhibited from the contralateral lateral line nerve. No evidence was found for inhibition from ipsilateral lateral line sensory organs.

Two types of lateral line afferents in the eel (Anguilla anguilla).

AbstractThe spontaneous and evoked discharges of eel lateral line sensory organs have been investigated. Each afferent nerve fibre has a well defined punctate receptive field, corresponding to a single canal organ. No axons were found to innervate more than one of these. All afferents pass through the Rarnus lat. dors. N.X. to the medulla oblongata. No peripheral unidirectional synapses exist in the nerve. Afferent axons are myelinated and belong to a large calibre (mode 12 μm) and a small calibre (mode 3 μm) axonal population in the nerve. The nerve contains about 800 myelinated axons at the level of its medullary entry, subserving approximately 100 sensory organs. In both groups rates of spontaneous discharge range from 0 c/s‐50 c/s. Both groups include extremely mechano‐sensitive units, and less sensitive units. The main difference between the slowly and rapidly conducting units is the more regular spontaneous firing pattern of the former group.

The activity of lateral-line efferent neurones in stationary and swimming dogfish.

ABSTRACT The activity of efferent neurones innervating lateral-line organs on the body of dogfish was followed by recording from filaments of cranial nerve X in 41 decerebrate preparations. The efferent nerves were not spontaneously active. Tactile stimulation to the head and body, vestibular stimulation and noxious chemical stimulation were followed by activity of the efferent nerves. In contrast, natural stimulation of lateral-line organs (water jets) did not reflexly evoke discharges from the efferent fibres. Reflex efferent responses were still obtained to mechanical stimulation even after the lateral-line organs had been denervated. Electrical stimulation of cranial nerves innervating lateral-lines organs was followed by reflex activity of the efferent fibres. But similar stimuli applied to other cranial nerves were equally effective in exciting the efferent system. Vigorous movements of the fish, involving the white musculature, were preceded and accompanied by activity of the efferent fibres which persisted as long as the white muscle fibres were contracting. Rhythmical swimming movements were accompanied by a few impulses in the efferent fibres grouped in bursts at the same frequency as the swimming movements. It is concluded that the efferent neurones cannot contribute to a feedback regulatory system because they are not excited by natural stimulation of the lateral-line sense organs. The close correlation found between efferent activity and body movement suggests that the efferent system might operate in a protective manner to prevent the sense organs from being over-stimulated when the fish makes vigorous movements.

Inhibition of Spontaneous Lateral-Line Activity by Efferent Nerve Stimulation

ABSTRACT Efferent nerve fibres innervating the lateral-line sense organs of the dogfish Scyliorhinus were stimulated with trains of stimuli while spontaneous afferent activity was monitored. Significant changes in spontaneous impulse frequency could be produced when the efferent nerves were stimulated by trains of pulses at frequencies between 20–100 sec−1; lower stimulus frequencies had no visible effect. The impulse frequency decreased or was totally inhibited during the stimulus period and for 150–200 msec following it. The inhibitory effect was very variable and declined with repetitive stimulation. Stimulation of the efferent nerves to inactive afferent units was followed after 500 msec by a brief low-frequency discharge.

Activity of Lateral-Line Sense Organs in Swimming Dogfish

ABSTRACT The activity of lateral-line sense organs was studied in swimming spinal dogfish by recording from filaments of the lateral-line nerve dissected in an anterior immobile part of the fish, the rest of the fish being free to move. In a non-swimming fish most of the receptors were spontaneously active, discharging at 15–20 impulses/sec. When the part of the body overlying the receptor was flexed, the impulse frequency was either enhanced or depressed, depending on the direction of movement. In swimming spinal dogfish the sense organs discharged in bursts at the same frequency as the swimming rhythm. The lateral-line receptors could provide information which would be useful in locomotory co-ordination, for the burst length, frequency, discharge frequency and number of impulses in the rhythmical discharge could all be correlated with the swimming movements.

The fine structure of the lateral-line sense organs of dogfish

The sense organs of the body lateral-line canals ofScyliorhinuswere examined with the electron microscope and shown to consist of supporting cells and two kinds of sensory cell. One type of sensory cell has the well-known structure of hair cells, bearing on its apical surface a group of stereocilia (6 to 25) associated with a single kinocilium. Each hair cell is innervated by a sensory nerve fibre and some also receive an efferent nerve supply. The second kind of sensory cell is similar in appearance, but differs at the apex in containing many vacuoles and in lacking stereocilia. There are many long microvilli and a single cilium which arises from a shallow pit. The internal structure of this cilium is variable, with the number of tubules in the outer ring ranging between 7 and 9 and with the inner pair consisting of double elements. This type of sensory cell is innervated by sensory nerve fibres and possibly by efferent fibres. The situation of the kinocilium of a hair cell in relation to the stereocilia is more variable than has been described in other hair cells while the cilium of the second sensory cell appears to bear no special relation to the microvilli. The accessory cells of the neuromast include basal and peripheral supporting cells, many of which produce a secretion, and a large secretory cell which is found at intervals at the edge of the organ. This cell has a convoluted surface and is full of vesicles.

Ferntastsinnesorgane von Oberflächenfischen

The arrangement of lateral line sense organs in 4 families of nonrelated surface feeding fishes is described. Although lateral line sense organs in these fishes show great variability they are all sensitive to surface waves. Morphological differences are emphasized and discussed functionally.

New lateral line sensory organs in Xenopus laevis Daudin.

DURING an investigation of a trematode infestation in Xenopus lævis a median ventral row of ‘lateral’ sensory organs was observed, which has not previously been described1. The observation was due to the nature of the infestation, and Fig. 1 is a photograph of a parasitized adult female toad. The parasites (Strigeid metacercariæ) encyst in all layers of the dermis beneath the lateral sense organs, and the position of these is emphasized by numerous large melanophores close to the cysts, while the rest of the skin remains paler than usual.

NEURAL MECHANISM OF THE LATERAL-LINE ORGAN OF FISH

1) Histological studies showed that the lateral-line organ of fish is innervated by a number of thin and thick nerve fibers. Each thick fiber, ramifying repeatedly, innervates several cells in the central part of the organ. Each thin fiber branches into many more and are connected to many peripheral cells.2) The electro-physiological, combined with histological, studies of the lateralline sense organ strongly suggests a peripheral neural mechanism of higher sensory organs, that is:A single end organ is supplied by many thin and thick fibers, among which the thinner fibers are probably related to the threshold, that is, to the perception of stimuli, while the thicker fibers to its discrimination.

Über die Reizung des Ferntastsinns bei Fischen und Amphibien

Fishes and aquatic amphibians are able to detect and locate moving bodies and even obstacles at some distance by means of their lateral-line sense organs (Ferntastsinn). As was shown experimentally, the main physical process involved in these reactions are certain local damming phenomena in front of the moving object (rise of pressure, displacement of water particles). Obstacles cause an alteration of the damming phenomena produced by the moving animal's body itself (increase of water resistance).Kramer's different view is rejected; he overlooked the existence of damming phenomena and was not aware of the fact thatXenopus laevis reacts to surface waves even when the animal is totally submerged.