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PubMedDate not supplied

The effect of aminoglycoside antibiotics on the lateral line organ of Aplocheilus lineatus (Cyprinodontidae).

The effect of neomycin and streptomycin on the lateral line system of fishes was studied behaviourally by testing the animal's ability to localize a wave source. Increasing doses of both substances produce increasing loss of lateral line reactions, up to total inexcitability. The toxicity of both antibiotics was very similar. Lateral line sensitivity recovered 1-3 days after antibiotic removal.

Animals↗
PubMed1995

The role of the lateral line in active drag reduction by clupeoid fishes.

The lateral-line canals, confined in clupeoid fishes to the two sides of the head, are centred on the two lateral recesses, where thin membranes separate the sea water in the lateral-line system from another fluid (perilymph) in that subcerebral canal which passes through the head between the two lateral recesses. Any pressure difference between the recesses can accelerate fluid in the subcerebral canal, but it is only the effective acceleration of that fluid (i.e. relative to the lateral acceleration of the head) which can tend to generate motions--sensed by neuromasts--in lateral-line canals near the lateral recesses. Furthermore, it is the same effective lateral acceleration (relative to that of the head) that is experienced by water in the thin boundary layer on the surface of the head, where it tends to generate 'crossflows' that may act to increase hydrodynamic resistance (i.e. drag) to the fish's normal swimming movements. These regular swimming movements produce oscillatory sideslip of the fish's head which, by itself, would give such substantial values to the effective acceleration that lateral-line sensors near the lateral recesses would be saturated during normal swimming movements. Any such permanent state of saturation seems rather unlikely. An alternative hypothesis is that the fish actively produces an oscillatory turning of the head, controlled by the sensory output of those same neuromasts in such a way that this output is kept to a minimum. Then that effective pressure difference, which is responsible for the effective lateral acceleration both of perilymph in the subcerebral canal and of sea water in the boundary layer on the head, would be minimised--with advantageous drag-reduction consequences. In order to test this hypothesis, a detailed hydrodynamic analysis was carried out. It suggested that, in order to minimise the effective pressure difference, the yaw angle (in radians) of the fish's head would need to be kept in phase with the sideslip velocity, their magnitudes being in a ratio of about 0.87 U-1 (where U is the swimming speed). Experiments on a swimming clupeoid fish confirmed these conclusions, both about phases and about magnitudes. By contrast, a purely passive response of the head to oscillatory sideforce on the caudal fin would be expected to give the yaw angle a substantial lag behind sideslip, along with a ratio of magnitudes much smaller than 0.87 U-1. Thus, the experiments seems to support the hypothesis regarding active control of drag reduction.

Animals↗
PubMed2005

Vocal pathways modulate efferent neurons to the inner ear and lateral line.

All sonic vertebrates face the problem of sound production interfering with their ability to detect and process external acoustic signals, including conspecific vocalizations. Direct efferent inputs to the inner ear of all vertebrates, and the lateral line system of some aquatic vertebrates, represent a potential mechanism to adjust peripheral sensitivity during sound production. We recorded from single efferent neurons that innervate the inner ear and lateral line in a sound-producing teleost fish while evoking fictive vocalizations predictive of the temporal features of natural vocalizations. The majority of efferent neurons showed an increase in activity that occurred in-phase with modulations in the fine temporal structure of the fictive vocalizations. Many of these neurons also showed a decrease in activity at fictive vocal offset. Efferents to the sacculus, the main auditory end organ, showed features especially well adapted for maintaining sensitivity to external acoustic signals during sound production. These included robust phase locking of efferent activity to each cycle of a fictive vocalization and a long-duration rebound suppression after each fictive vocalization that could provide a rapid, long-lasting period of sensitization to external acoustic stimuli such as the call of a conspecific. These results suggest that efferent activation by the vocal motor system can directly modulate auditory sensitivity to self-generated sounds and maintain sensitivity to ongoing external sounds. Given the conserved organization of the auditory efferent system across vertebrates, such mechanisms may be operative among all sonic vertebrates.

Animals↗
PubMed1990

Neural pathway for aggressive display in Betta splendens: midbrain and hindbrain control of gill-cover erection behavior.

Horseradish peroxidase (HRP) was used to identify parts of the presumptive neural pathway for gill cover erection, a behavioral display pattern performed by Siamese fighting fish (Betta splendens) during aggressive interactions. Motor, motor integration and sensory areas were identified in the medulla and mesencephalon. Motor neurons of the dilator operculi muscle, the effector muscle for gill cover erection, are located in the lateral and medial parts of the caudal trigeminal motor nucleus. Iontophoretic injections of HRP into the lateral trigeminal motor nucleus resulted in labeled cell bodies in two motor areas (medial part of the trigeminal motor nucleus, anterior part of the motor nucleus of cranial nerve IX-X), two parts of the reticular formation (medial and inferior reticular areas), and two nuclei of the octavolateralis system (nucleus medialis, magnocellular octaval nucleus). The HRP injections in the medial part of the caudal trigeminal motor nucleus resulted in labeled cells in the lateral part of the nucleus and in the medial reticular nucleus. Discrete injections of HRP into nucleus medialis revealed a strong axonal projection that terminated in the torus semicircularis. The medial reticular area and both of the octavolateralis nuclei received projections from their contralateral counterparts. Connections between motor areas, and between parts of the reticular formation, may coordinate the performance of gill cover erection with other behavioral patterns used during aggressive display. Connections with the octavolateralis system may provide information on the strength of an opponent's tail beats via the lateral-line system, as well as vestibular information about the fish's own orientation during aggressive display. The organization of inputs to the trigeminal motor nucleus in Betta, a perciform fish, was found to differ from that reported in the common carp, a cypriniform fish. These differences may underlie the different behavioral capabilities of the two groups of fish.

Afferent Pathways↗
PubMed1990

Behavioral and neurophysiological assessment of lateral line sensitivity in the mottled sculpin, Cottus bairdi.

1. The unconditioned feeding response of the mottled sculpin, Cottus bairdi, was used to measure threshold sensitivity of the lateral line system to a vibrating sphere as a function of stimulus position (i.e., sphere near head, trunk or tail) and vibration frequency. In addition, extracellular recording techniques were used to measure threshold sensitivity curves for posterior lateral line nerve fibers for the same stimulus positions used for measuring trunk sensitivity in behavioral measurements. 2. For all stimulus positions, behaviorally-measured threshold sensitivity was relatively independent of vibration frequency from 10 to 100 Hz when defined in terms of water acceleration, rather than velocity or displacement. Best thresholds for stimuli placed 15 mm away from the head were around -75 dB re: 1m/s(2), approximately 20 dB less than that for stimuli placed at the same distance near the tail. Trunk sensitivity was intermediate. 3. Physiologically-measured threshold sensitivity, in terms of acceleration, was also relatively independent of of frequency from 10 to 100 Hz in most fibers. A smaller number of fibers showed a decline in acceleration sensitivity after 10-30 Hz, with the rate of decline being equivalent to equal velocity sensitivity. Best sensitivity of all fibers fell between -40 and -70 dB re: 1m/s (2). 4. These results indicate that (a) behavioral thresholds are based on acceleration-sensitive endorgans--most likely lateral line canal (rather than superficial) neuromasts, (b) behavioral performance can be accounted for on the basis of information from a single population of fibers, and (c) sensitivity varies along the fish's body in a manner that corresponds to the size and distribution of neuromasts.

Behavior, Animal↗
PubMed2001

Expression of proneural and neurogenic genes in the zebrafish lateral line primordium correlates with selection of hair cell fate in neuromasts.

Expression of a mouse atonal homologue, math1, defines cells with the potential to become sensory hair cells in the mouse inner ear (Science 284 (1999) 1837) and Notch signaling limits the number of cells that are permitted to adopt this fate (Nat. Genet. 21 (1999) 289; J. Neurocytol. 28 (1999) 809). Failure of lateral inhibition mediated by Notch signaling is associated with an overproduction of ear hair cells in the zebrafish mind bomb (mib) and deltaA mutants (Development 125 (1998a) 4637; Development 126 (1999) 5669), suggesting a similar role for these genes in limiting the number of hair cells in the zebrafish ear. This study extends the analysis of proneural and neurogenic gene expression to the lateral line system, which detects movement via clusters of related sensory hair cells in specialized structures called neuromasts. We have compared the expression of a zebrafish atonal homologue, zath1, and neurogenic genes, deltaA, deltaB and notch3, in neuromasts and the posterior lateral line primordium (PLLP) of wild-type and mib mutant embryos. We describe progressive restriction of proneural and neurogenic gene expression in the migrating PLLP that appears to correlate with selection of hair cell fate in maturing neuromasts. In mib mutants there is a failure to restrict expression of zath1 and Delta homologues in the neuromasts revealing similarities with the phenotype previously described in the ear.

Animals↗
PubMed1987

Electron microscopical evidence for common inner ear and lateral line efferents in urodeles.

The efferents of the lateral line system and the inner ear were examined in urodeles using retrograde labelling with horseradish peroxidase (HRP). The Golgi-like filling thus achieved allowed tracing of the axons of efferent cells from one inner ear to the other and from the lateral line nerves into both inner ears. Electron microscopic examination of the inner ear revealed HRP label only in vesicle filled terminals on hair cells traditionally considered as efferent synapses. These data confirm earlier claims of common bilateral inner ear and lateral line efferents. In addition, the efferent nature of retrogradely labelled rhombencephalic cells is proven by their continuity with ultrastructurally identified efferent synapses in the inner ear.

Animals↗
PubMed1995

Teeth and tooth nerves.

(1) Although our knowledge on teeth and tooth nerves has increased substantially during the past 25 years, several important issues remain to be fully elucidated. As a result of the work now going on at many laboratories over the world, we can expect exciting new findings and major break-throughs in these and other areas in a near future. (2) Dentin-like and enamel-like hard tissues evolved as components of the exoskeletal bony armor of early vertebrates, 500 million years ago, long before the first appearance of teeth. It is possible that teeth developed from tubercles (odontodes) in the bony armor. The presence of a canal system in the bony plates, of tubular dentin, of external pores in the enamel layer and of a link to the lateral line system promoted hypotheses that the bony plates and tooth precursors may have had a sensory function. The evolution of an efficient brain, of a head with paired sense organs and of toothed jaws concurred with a shift from a sessile filter-feeding life to active prey hunting. (3) The wide spectrum of feeding behaviors exhibited by modern vertebrates is reflected by a variety of dentition types. While the teeth are continuously renewed in toothed non-mammalian vertebrates, tooth turnover is highly restricted in mammals. As a rule, one set of primary teeth is replaced by one set of permanent teeth. Since teeth are richly innervated, the turnover necessitates a local neural plasticity. Another factor calling for a local plasticity is the relatively frequent occurrence of age-related and pathological dental changes. (4) Tooth development is initiated through interactions between the oral epithelium and underlying neural crest-derived mesenchymal cells. The interactions are mediated by cell surface molecules, extracellular matrix molecules and soluble molecules. The possibility that the initiating events might involve a neural component has been much discussed. With respect to mammals, the experimental evidence available does not support this hypothesis. In the teleost Tilapia mariae, on the other hand, tooth germ formation is interrupted, and tooth turnover ceases after local denervation. (5) Prospective dental nerves enter the jaws well before onset of tooth development. When a dental lamina has formed, a plexus of nerve branches is seen in the subepithelial mesenchyme. Shortly thereafter, specific branches to individual tooth primordia can be distinguished. In bud stage tooth germs, axon terminals surround the condensed mesenchyme and in cap stage primordia axons grow into the dental follicle.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

NGF and IL-1beta are co-localized in the developing nervous system of the frog, Xenopus laevis.

NGF, a neurotrophic factor best known for its role in promoting cell survival, regulates many neurodevelopmental processes, including synaptic plasticity, neurite outgrowth and programmed cell death. Although there is a large amount of data regarding NGF in the developing nervous system of many species, there is little known about its regulation and role in the frog, Xenopus laevis. In this report, immunocytochemistry was used to characterize NGF protein expression in developing tadpoles. Protein expression was analyzed in tadpoles from stage 44/45 through stage 50, a period of development characterized by extensive neurite outgrowth, neuronal differentiation and an initial period of programmed cell death. Similar to other species, NGF was expressed in sensory cells and tissues, including the inner ear, eye, olfactory system, lateral line organs, papillae in the oral cavity, and gills tufts. In addition, NGF was expressed in specific cells in the central nervous system, cranial and dorsal root ganglia, spinal sensory and motoneurons, and muscle tissues in the tail and body cavity. In the mammalian nervous system, the cytokine, interleukin-1beta (IL-1beta) induces expression of NGF. In this report, double-label immunocytochemistry was used to determine the relationship between NGF and IL-1beta. Results showed most cell types and/or tissues that expressed NGF also expressed IL-1beta. However, NGF was typically associated with cellular and nuclear membranes, whereas IL-1beta appeared in the cytoplasm and nucleolus. The nuclear localization of IL-1beta supports the idea that it regulates gene transcription in the frog. The appearance of NGF and IL-1beta in the same cells suggests they may interact to influence neural development.

Animals↗
PubMed1998

Descending neural projections to the spinal cord in the channel catfish, Ictalurus punctatus.

Retrograde transport of horseradish peroxidase was used to determine the descending projections to the spinal cord in an otophysan fish, the channel catfish, Ictalurus punctatus. The majority of cells projecting to the spinal cord are located in the reticular formation, which is organized into rhombomeric segments. Vestibulospinal neurons are located in the descending, magnocellular, and tangential octaval nuclei, as well as in the medial octavolateralis nucleus of the lateral line system. Cells in the facial lobe project to the spinal cord. Additionally, axons of cells of the trigeminal system and the nucleus of the lateral lemniscus project caudally into the spinal cord. In the midbrain, descending spinal projections arise from cells of the medial longitudinal fasciculus and the red nucleus. More rostrally, cells of the ventrolateral thalamus, dorsal periventricular hypothalamus, central pretectal and magnocellular preoptic nuclei also project to the cord. The results of this study indicate that there are a number of homologies in the descending systems of bony fishes and other vertebrate taxa, including tetrapods. We also provide further evidence that a red nucleus is present in the brains of bony fishes and is therefore a primitive vertebrate character antedating the evolution of tetrapods.

Animals↗
PubMed1994

THE RELATIONSHIP BETWEEN THE LENGTH OF THE CUPULAE OF FREE NEUROMASTS AND FEEDING ABILITY IN LARVAE OF THE WILLOW SHINER GNATHOPOGON ELONGATUS CAERULESCENS (TELEOSTEI, CYPRINIDAE)

Free mechanosensory neuromasts of larval fishes have been described as playing a complementary role to vision in feeding behaviour (Disler, 1971; Iwai, 1972a,b). In certain species or under limited conditions, free neuromasts play a major role in detecting prey. The larvae of mottled sculpin Cottus bairdi can feed on Artemia in the dark by using free neuromasts (Jones and Janssen, 1992). Artificially blinded surface-feeding Aplocheilus lineatus can detect insects on the water surface by means of free neuromasts (Muller and Schwarts, 1982; Tittel et al. 1984; Bleckmann, 1988; Bleckmann et al. 1989). Furthermore, vibrations produced by swimming crustaceans are known to be a potent natural stimulus for the lateral line system in the Antarctic fish Pagothenia borchgrevinki (Montgomery and Macdonald, 1987; Montgomery, 1989). We found that larvae of a plankton feeder, the willow shiner Gnathopogon elongatus caerulescens (Sauvage) (Cypriniformes, Cyprinidae), fed on nauplii of Artemia in complete darkness. Ototoxic compounds, such as streptomycin, have been shown to disturb the function of the lateral line organ or free neuromasts (Kaus, 1987; Blaxter and Fuiman, 1989; Janssen, 1990; Jones and Janssen, 1992). Willow shiner larvae treated with streptomycin sulphate no longer feed on Artemia in the dark (Y. Mukai, in preparation). The willow shiner inhabits calm lakes and feeds on zooplanktonic prey (Nakamura, 1949). The larvae show a high sensitivity to minute water displacements. From these observations and from our findings, it appears that larval willow shiner must feed on zooplankton by using free neuromasts in the dark. In larval willow shiner, the vane-like cupulae of the free neuromasts protrude from the body surface and the long cupulae are 100-250 microm in length (Mukai and Kobayashi, 1991). The prey is detected by the free neuromasts as a result of a slight bending of the cupula in response to local water movements. The shape of the cupula, especially its length, must therefore be related to the sensitivity of the free neuromast, as inferred from the results of Coombs and Janssen (1989) and van Netten and Kroese (1989).

Journal Article↗
PubMed1976

Gustatory pathways in the bullhead catfish. 1. Connections of the anterior ganglion.

The central projections of the external gustatory system in bullhead catfish were examined using orthograde degeneration and retrograde transport of horseradish peroxidase (HRP) techniques. Both large and small cells were observed in the anterior ganglion which contains a mixture of elements from the trigeminal, facial and anterior lateral line nerves. Some of the large cells on the lateral margin of the ganglion were found to belong to the lateral line system. No separation of trigeminal and facial nerve connections could be made. Using HRP, the relation between the barbels and specific ganglion regions was determined. The dorsalmost portion of the ganglion received recurrens nerve inputs (from taste buds on the trunk); the rostromedial portion of the ganglion, from the maxillary and mandibular barbel nerves. The facial lobe (similar to part of the n. solitarius) was found to be divided into lobules by fascicles of nerve fibers. The lateral lobule received input only from the dorsal-most part of the ganglion (recurrens nerve: trunk receptors); the intermediate lobule from the rostro-lateral part of the ganglion (nasal barbel); and the medial lobule from the ventral areas of the ganglion (maxillary and mandibular barbels). Thus a topographical relationship exists between the different taste receptor groups and their locus of representation in the facial lobe. The trunk receptors connect to the lateral lobule; the nasal barbel receptors to the intermediate lobule, and the maxillo-mandibular receptors to the medial lobule.

Afferent Pathways↗
PubMed1999

Sonic motor nucleus and its connections with octaval and lateral line nuclei of the medulla in a rockfish, Sebastiscus marmoratus.

The sonic motor nucleus and its fiber connections were examined in a rockfish, Sebastiscus marmoratus by means of tracer methods using horseradish peroxidase (HRP), biocytin, and carbocyanine dye (DiI). Sebastiscus has a swimbladder and a pair of extrinsic sonic/drumming muscles. The sonic muscle is ipsilaterally innervated by the occipital nerve which is composed of two ventral roots arising from the sonic motor nucleus. The sonic motor neurons are distributed in the most ventral part of the ventral column from the caudal medulla to the rostral spinal cord, and form a ventrally located columnar nucleus. Each neuron in this nucleus possesses a long thick dendrite and several short dendrites. The long dendrite extends dorsolaterally and branches in the lateral funiculus, whereas the short dendrites branch around their cell bodies. After biocytin injections into the sonic motor nucleus, two groups of premotor neurons were retrogradely labeled bilaterally, one in the dorsomedial portion of the descending octaval nucleus (DO) and the other in the medial zone of the reticular formation (RF) in the medulla. The DO premotor neurons were multipolar with several dendrites branching near the cell bodies, and the RF premotor neurons were bipolar. One of the two dendrites of the RF premotor neurons extends laterally into the ventral portion of the DO, and the other dendrite extends into the ventromedial area in the medulla. In the ventromedial dendritic field of the RF premotor neurons, descending fibers arising from the optic tectum (TO) and torus semicircularis (TS) traverse in the tractus tectobulbaris and terminate bilaterally. After DiI insertion into the ventromedial dendritic field, retrogradely labeled neurons were found bilaterally in the TS and TO. The majority of tectal neurons were located in the stratum griseum centrale. These neurons had two short basal dendrites branching in the cell layer and a long apical dendrite extending to the stratum fibrosum et griseum superficiale and stratum opticum. The toral neurons were bipolar and were distributed throughout the TS. Furthermore, biocytin injections into the medial nucleus of the lateral line system revealed that the nucleus projects bilaterally to the RF premotor neurons. These results show that premotor neurons for the sonic motor nucleus are located in the dorsomedial portion of the DO and the medial zone of the RF in the medulla. It is suggested that the sonic motor nucleus receives auditory input via the DO premotor neurons and input from RF premotor neurons which receive lateral line input via the medial nucleus, vestibular input through the lateral dendrite extending into the ventral portion of the DO, and information from the TO and TS via the tractus tectobulbaris.

Air Sacs↗
PubMed2004

Lateral line receptors: where do they come from developmentally and where is our research going?

The lateral line system is composed of both mechanoreceptors, which exhibit little variation in structure between taxonomic groups, and electroreceptors, which exhibit considerably more variation. Cathodally sensitive ampullary electroreceptors are the primitive condition and are found in agnathans, chondrichthyans, and most osteichthyans. Aquatic amphibians also have ampullary electroreceptors for at least part of their life cycle. The more recently evolved anodally sensitive ampullary electroreceptors and tuberous electroreceptors are only found in four groups of teleost fishes. The basic ontogenetic unit of lateral line development is the dorsolateral placode. Primitively, there are six pairs of placodes, which pass through sequential stages of development into lateral line receptors. There is no question about the origin of primitive mechanoreceptors or electroreceptors, however, we do not have a good understanding of the origin of teleost mechanoreceptors and their ampullary or tuberous electroreceptors; do they come exclusively from dorsolateral placodes or from neural crest or even general ectoderm? A second intriguing lateral line question is how certain teleost fish groups evolved tuberous electroreceptors. Electroreception appears to have re-evolved at least twice in teleosts after being lost during the neopterygian radiation. It has been suggested that the development of tuberous electroreceptors might be due to changes in placodal patterning or a change in the general ectoderm that placodes arise from. Unfortunately, our understanding of lateral line origins in fishes is very sketchy, and, if we are to answer such an evolutionary question, we first need more complete information about lateral line development in a variety of fishes, which can then be combined with gene expression data to better interpret lateral line receptor development.

Animals↗
PubMed1989

Sensory systems and behavior of premetamorphic and metamorphic leptocephalous larvae.

The superorder Elopomorpha (orders Anguilliformes, Elopiformes and Notacanthiformes) is characterized by the presence of a unique larval stage termed the leptocephalus. The basic morphology, chemical composition, developmental pattern, and behavior of premetamorphic and metamorphic leptocephali are reviewed. The eyes, olfactory organs and pores of the lateral-line system are well developed, suggesting that these sensory structures play an important role in larval behavior. Premetamorphic larvae are pelagic and in some elopomorphs subsequent development is associated with migration to coastal waters where metamorphosis takes place. The factors controlling onshore migration, as well as the metamorphic trigger(s), are unknown. The possible relationships between sensory systems and behavioral changes during the different phases of larval development are presented.

Animals↗
PubMed2006

Prey-capture in the African clawed toad (Xenopus laevis): comparison of turning to visual and lateral line stimuli.

Separately delivered visual and lateral line stimuli elicit similar but not identical orientation and approach by intact, sighted Xenopus. Response frequencies for visual stimuli declined sharply for distant or caudal stimuli while those for lateral line stimuli changed little. Turn angles correlated highly with stimulus angles but were smaller on average, so regression slopes were less than one. Regression slopes were smaller for visual than for lateral line stimuli, but this apparent difference was due to different distributions of stimulus distance interacting with the toad's rotation center. Errors in final headings, most often under-rotations, did not differ by modality. Frequencies of lunges and arm capture movements were higher for visual stimuli both overall and especially for rostral proximal stimuli. The results demonstrate accurate orientation by sighted Xenopus to visual and lateral line stimuli; they are consistent with expectations based on in-register tectal maps. Orientation to lateral line stimuli is similar to previous results with blinded animals, revealing no heightened acuity in the latter. Modality differences indicate that the lateral line system is better for omnidirectional orientation and approach to distant stimuli whereas the visual system is more attuned to nearby rostral stimuli and more apt to mediate strikes.

Analysis of Variance↗
PubMed1991

Morphogenetic development of the area octavolateralis in the cichlid fish Oreochromis mossambicus.

In the cichlid fish Oreochromis mossambicus the area octavolateralis in the brain stem was studied using histological techniques and labelling of afferents from the inner ear and the lateral line system with horseradish peroxidase (HRP). Adult fish and fish larvae aged 2, 4, 7, 10, and 15 days post hatching were investigated in order to analyze the ontogenetic development of these sensory systems during the critical phase of maturation from relatively immobile stages to actively swimming larvae. In adult Oreochromis seven nuclei can be detected in the octavolateral area while in the larvae a steady differentiation from a mostly periventricular concentration of perikarya in the first two days post hatching via increasing accumulations of neuronal cell bodies in the more peripheral regions up to four discernible nuclei in the age of 15 days post hatching was observed. The HRP-labelling of afferents from the lateral line organ and the inner ear in early stages indicates that the sensory organs precedes the histologically detectable differentiation in the octavolateral area. Both sensory components are clearly separated already in very early developmental stages.

Aging↗
PubMed1988

The area acustico-vestibularis of Discoglossus pictus. II. The primary afferent projections.

In the present report the primary projections to the dorsal rhombencephalic alar plate (area acustico-vestibularis, AAV) of the adult anuran amphibian Discoglossus pictus have been studied by means of the anterograde transport of horseradish peroxidase (HRP). As in Alytes cisternasii, other member of the family Discoglossidae, no primary afferent fibers to the AAV were found from nerves other than the VIIIth cranial nerve. No remanent of the lateral line system in the adult stage is present. The projections of the dorsal root of nerve VIIIth distribute over the dorsal nucleus and rostrally reach the aspect of the cerebellum. Caudally projects to the large cells of the ventral nucleus and terminate caudally, in the dorsolateral neuropil, at levels coincident with the IX motor nucleus. The projection of the ventral root also reaches the cerebellum in its lateral aspect but also fibers to the nucleus cerebelli were observed. The extensive projection to the ventral nucleus is also continued caudally to the caudal nucleus and ends around the solitary tract. Main terminal fields were located in two neuropils, one subventricular and other in an intermediate position. In addition, from both nerve branches, fibers leave the AAV and reach the reticular formation. Particularly, fibers from the posterior branch enter the superior olivary nucleus. Retrograde labeled neurons in the vicinity of the VII motor nucleus are interpreted as efferent cells to the labyrinth.

Animals↗