scholarly journals Proliferation of superficial neuromasts during lateral line development in the Round Goby, Neogobius melanostomus

2018 ◽  
Author(s):  
J. M. Dickson ◽  
J. A. Janssen

ABSTRACTMembers of the family Gobiidae have an unusual lateral line morphology in which some of the lateral line canal segments do not develop or enclose. This loss of lateral line canal segments is frequently accompanied by proliferation of superficial neuromasts. Although the proliferation of superficial neuromasts forms intricate patterns that have been used as a taxonomic tool to identify individual gobiid species, there has never been a detailed study that has documented the development of the lateral line system in gobies. The Round Goby, Neogobius melanostomus, is the focus of this study because the absence of the lateral line canal segments below the eye are accompanied by numerous transverse rows of superficial neuromasts. Our results suggest that the origin of some of these superficial neuromast lines could be the result of single presumptive canal neuromasts that have proliferated after canal enclosure is arrested. Many of the intricate patterns of neuromasts observed in gobiids develop from a simplified pattern of neuromast that is very similar among different species of gobies. The proliferation of superficial neuromasts has evolved several times in fish families such as the tetras, gobies, and sculpins, and may provide an adaptive advantage to ‘tune’ the lateral line system for different environments and prey types.SIGNIFICANCE STATEMENTUnderstanding the development of different lateral line morphologies can provide insights into how these morphologies have convergently evolved in many fish taxa. This is the first study to document the progression of the development of the reduced lateral line morphology. This study shows evidence that the developmental origins of orthogonal lines of superficial neuromasts posterior to the eye are not neomorphic lines, but in fact arise from precursor neuromasts that seem to be analogous to presumptive canal neuromasts.

Author(s):  
J. Mørup Jørgensen

The lateral-line system of water-living lower vertebrates is provided with mechanoreceptors enabling the animals to detect water displacements, either caused by moving objects such as prey, predators or neighbours in a school or by deformations of pressure waves from the swimming animal caused by other objects. Cyclostomes, some fish and water–living amphibians have their lateral-line organs situated superficially in the epidermis as free neuromasts, while most fish besides these neuromasts possess a canal system in the dermis. Ordinarily the lateral line canal system consists of a few canals on the sides of the head and a trunk canal. In herring, however, the canal system is confined to the head and opercule. It forms a very richly branched system with numerous pores which connect the canal fluid with the surrounding sea water.


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.


2019 ◽  
Vol 189 (1) ◽  
pp. 1-46 ◽  
Author(s):  
Murilo N L Pastana ◽  
Flávio A Bockmann ◽  
Aléssio Datovo

Abstract The lateral-line system has been traditionally recognized as an important source of phylogenetic information for different groups of fishes. Although extensively studied in Siluriformes and Cypriniformes, the lateral-line system of Characiformes remained underexplored. In the present study, the anatomy of the cephalic lateral-line canals of characiforms is described in detail and a unifying terminology that considers the ontogeny and homologies of the components of this system is offered. Aspects of the arrangement of lateral-line canals, as well as the number, location and size of canal tubules and pores, resulted in the identification of novel putative synapomorphies for Characiformes and several of its subgroups. The study also revised synapomorphies previously proposed for different characiform families and provided comments on their observed distribution across the order based on extensive taxon sampling. Information from the ontogenetic studies of the cephalic lateral-line canal system and a proposal for the proper use of these data to detect truncations in the development of the lateral-line canals across the order is also offered.


1995 ◽  
Vol 349 (1328) ◽  
pp. 119-134 ◽  

The head of adult hagfishes (jawless craniates, Myxinoidea) of the family Eptatretidae displays a number of skin grooves of uncertain origin. These grooves have been homologized to the neuromast lines of other craniates, and they are innervated by two ganglionated cranial nerves that have been interpreted as lateral line nerves. The grooves do not, however, contain the compound receptors that are typical of a lateral line (i.e. neuromasts or electroreceptors), and both their development and function have remained enigmatic. To elucidate the embryonic origin of the grooves (which should develop from placodes if they are homologues of the lateral line system), embryos of Pacific hagfish were examined by means of threedimensional reconstructions from serial sections. Because of the scarcity of specimens of embryonic hagfishes, only two embryos were reconstructed, but these reconstructions clearly show that a number of placodes and placodal derivatives (i.e. sensory ridges, receptor primordia, and cranial ganglia) occur in the head of embryonic eptatretid hagfishes. Some of these placodes correspond to the lens and epibranchial placodes of other craniates, but there are also three other placodes which represent possible homologues of lateral line placodes. The topology of the placodes in this latter group corresponds to the topology of the grooves of adult hagfishes, and we therefore reach three conclusions: (i) that an embryonic lateral line system is present in hagfishes; (ii) that the grooves of adult hagfishes in all probability derive from lateral line placodes; and (iii) that the presence of lateral line placodes is a primitive character of craniates.


2015 ◽  
Vol 113 (2) ◽  
pp. 657-668 ◽  
Author(s):  
Rafael Levi ◽  
Otar Akanyeti ◽  
Aleksander Ballo ◽  
James C. Liao

The ability of fishes to detect water flow with the neuromasts of their lateral line system depends on the physiology of afferent neurons as well as the hydrodynamic environment. Using larval zebrafish ( Danio rerio), we measured the basic response properties of primary afferent neurons to mechanical deflections of individual superficial neuromasts. We used two types of stimulation protocols. First, we used sine wave stimulation to characterize the response properties of the afferent neurons. The average frequency-response curve was flat across stimulation frequencies between 0 and 100 Hz, matching the filtering properties of a displacement detector. Spike rate increased asymptotically with frequency, and phase locking was maximal between 10 and 60 Hz. Second, we used pulse train stimulation to analyze the maximum spike rate capabilities. We found that afferent neurons could generate up to 80 spikes/s and could follow a pulse train stimulation rate of up to 40 pulses/s in a reliable and precise manner. Both sine wave and pulse stimulation protocols indicate that an afferent neuron can maintain their evoked activity for longer durations at low stimulation frequencies than at high frequencies. We found one type of afferent neuron based on spontaneous activity patterns and discovered a correlation between the level of spontaneous and evoked activity. Overall, our results establish the baseline response properties of lateral line primary afferent neurons in larval zebrafish, which is a crucial step in understanding how vertebrate mechanoreceptive systems sense and subsequently process information from the environment.


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.


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