Ear and Lateral Line of Vertebrates: Organisation and Development


In vertebrates, perception of movement and sound is accomplished by the lateral line and inner ear sensory systems. These systems sense reverberations, movement and acceleration by transducing mechanical stimuli from the environment into electrical signals by means of mechanosensory hair cells. Vestibular and auditory hair cells have associated sensory neurons that transmit these signals from the periphery to the central nervous system. During development, cranial sensory systems arise from an initially homogeneous population of cells that ultimately give rise to discrete sensory structures. Although the demands for auditory and vestibular sensation differ between species and environments, vertebrates use common cell types, genetic programmes and molecules to achieve the development of these mechanosensory organs. In this article, the structure and function of the mechanosensory hair cells, lateral line and inner ear and how these systems develop across species are discussed, and as well as the innervation of these systems.

Key Concepts:

  • The vertebrate inner ear is composed of both auditory and vestibular components.

  • Both the lateral line and the inner ear are derived from embryonic structures known as cranial placodes.

  • All cranial placodes originate from a homogenous group of cells known as the preplacodal ectoderm.

  • Hair cells are structurally and functionally similar in both auditory and lateral line systems.

  • The adult lateral line mediates sensation of movement in the aquatic environment of fishes and frogs.

  • Embryonic posterior lateral line development is accomplished by the preā€patterned posterior lateral line primordium.

  • The lateral line is an experimentally accessible model for studying mechanosensory system development and biology.

Keywords: lateral line; inner ear; mechanosensory hair cells; development; vestibular; auditory; cranial placodes; primordium

Figure 1.

Mechanosensory hair cells: Schematic showing general features of the hair cell. The apical end includes stereocilia and kinocililum‐containing hair bundle, tip links and mechanotransduction channel. Basal features include the ribbon synapse, afferent and efferent innervation. Note that the ribbon synapse was initially discovered in photoreceptors, where it has a ‘ribbon‐like’ shape, but it appears more circular in hair cells.

Figure 2.

Schematic of the inner ear and its associated sensory structures, the maculae and the cristae. (a) Depiction of the inner ear showing the three semicircular canals in blue, these canals contain the vestibular sensory structures, the cristae. Illustrated in green is the vestibular region containing the utricle and saccule, which harbour the otolith organs, the maculae. Nerve fibres of the SAG are shown in red, and the auditory component of the inner ear, the cochlea, is depicted in purple. (b) Illustration of the maculae showing in detail the otolithic membrane which covers the stereocilia of the sensory hair cells, the associated support cells and nerve fibres. (c) Representative image of the cristae contained in the semicircular canals, kinocilium of the hair cells projects into the cupula.

Figure 3.

Illustration of early otic development and patterning. (a) Dorsal view of a generalised embryo at the end of gastrulation, the horseshoe‐shaped PPE domain is depicted in red. This domain adjoins the neural plate (light blue) and is lateral to the forming neural crest (green), in blue is the non‐neural ectoderm. The PPE is defined at this stage by the expression of the factors six, dlx and Eya. (a′) A unilateral cross‐section at the indicated axis and the same time point as in (A). The neural plate (blue) and the cephalic mesoderm (green) secrete Fgfs that induce the PPE (red); Wnt and BMP inhibitors are expressed in the PPE. (b) Early neurulation stage, precursors for both the otic and epibranchial placodes are contained in a common domain (purple) defined by the expression of Foxi1 and Dlx3/4. (b′) Cross‐section of an early neurulation stage embryo at the indicated axis (b). Continued Fgf signalling from the neural tube and cephalic mesoderm induce the common otic/epibranchial domain. (c) Neurulation stage embryo illustrating the segregation of the early otic placode in blue, defined by its expression of Sox3, Pax2 and Pax8. (c′) Cross‐section of a neurulation stage embryo at the indicated axis (c). At this stage, Wnt signalling from the neural tube works in conjunction with the Notch pathway to define the early otic domain, continued Fgf signalling from the cephalic mesoderm defines the epibranchial domain. (d) Illustration of the signalling pathways involved in early otic regionalisation. Fgf defines the anterior whereas an RA gradient is responsible for the posterior; Wnt signalling imparts dorsal identity whereas hH signalling sets up the ventral axis. (d′) Factors that define molecular asymmetries during otic patterning: Dlx5, Pax2 for dorsal; Pax5, Hmx2 for anterior; Otx2 for ventral and Fst1 for posterior.

Figure 4.

Lateral line mechanosensory hair cells: (a) Schematic showing lateral views of larval (7 days postfertlisation) and adult (6 months postfertilisation) zebrafish lateral line patterns (red dots). In the adult, neuromasts are arranged in dorsal–ventral oriented ‘stitches’ on the trunk, and in dermal canals on the head. (b) Idealised schematic of a cross‐section of a single lateral line neuromast showing two representative hair cells that extend stereocilia and kinocilia (encased in the gelatinous cupula and stabilised by the actin‐rich cuticular plate at the apical end of the hair cells) into the environment to sense changes in water current. Hair cells are surrounded by supporting cells and mantle cells and are innervated by afferent and efferent axons. (c) Schematic showing a top‐down view of kinocilia and stereocilia orientation in dorsoventral and anterioposterior sensing neuromasts. All schematics are not drawn to scale.

Figure 5.

Development of the posterior lateral line: (a) 30 hpf zebrafish embryo. The posterior lateral line ganglion is positioned behind the ear, with posterior lateral line (red) migrating down the trunk. (b) Rosette renewal in the posterior lateral line. Leading region progenitors (red) give rise to columnar daughter cells (blue), which constrict apically to give rise to a nascent rosette. Mature rosettes are deposited at the trailing part of the posterior lateral line. Colours indicate the same groups of cells over time. (c) Model of apical constriction in the leading portion of the posterior lateral line. Fgf activates the Ras‐MAPK pathway, which likely transcriptionally activates shroom3. Shroom3 anchors Rho‐kinase (Rock) in the apical domain of the cell, activating the actomysoin cytoskeleton. (d) Lateral line axon extension. Pioneer axons (dark green) extend with the primordium. Follower axons (light green) extend later.



Abelló G, Khatri S, Giráldez F and Alsina B (2007) Early regionalization of the otic placode and its regulation by the Notch signaling pathway. Mechanisms of Development 124: 631–645.

Ahrens K and Schlosser G (2005) Tissues and signals involved in the induction of placodal Six1 expression in Xenopus laevis. Developmental Biology 288: 40–59.

Aman A, Nguyen M and Piotrowski T (2011) Wnt/β‐catenin dependent cell proliferation underlies segmented lateral line morphogenesis. Developmental Biology 349: 470–482.

Aman A and Piotrowski T (2008) Wnt/beta‐catenin and Fgf signaling control collective cell migration by restricting chemokine receptor expression. Developmental Cell 15: 749–761.

Bhattacharyya S, Bailey AP, Bronner‐Fraser M and Streit A (2004) Segregation of lens and olfactory precursors from a common territory: cell sorting and reciprocity of Dlx5 and Pax6 expression. Developmental Biology 271: 403–414.

Bok J, Raft S, Kong K‐A et al. (2011) Transient retinoic acid signaling confers anterior‐posterior polarity to the inner ear. Proceedings of the National Academy of Sciences of the USA 108: 161–166.

Boldajipour B, Mahabaleshwar H, Kardash E et al. (2008) Control of chemokine‐guided cell migration by ligand sequestration. Cell 132: 463–473.

Breau MA, Wilson D, Wilkinson DG and Xu Q (2012) Chemokine and Fgf signalling act as opposing guidance cues in formation of the lateral line primordium. Development 139: 2246–2253.

Bricaud O, Chaar V, Dambly‐Chaudière C and Ghysen A (2001) Early efferent innervation of the zebrafish lateral line. Journal of Comparative Neurology 434: 253–261.

Cernuda‐Cernuda R and García‐Fernández JM (1996) Structural diversity of the ordinary and specialized lateral line organs. Microscopy Research and Technique 34: 302–312.

Ernst S, Liu K, Agarwala S et al. (2012) Shroom3 is required downstream of FGF signalling to mediate proneuromast assembly in zebrafish. Development 139: 4571–4581.

Faucherre A, Pujol‐Martí J, Kawakami K and López‐Schier H (2009) Afferent neurons of the zebrafish lateral line are strict selectors of hair‐cell orientation. PLoS One 4: e4477.

Ghysen A, Dambly‐Chaudière C, Coves D, de la Gandara F and Ortega A (2012) Developmental origin of a major difference in sensory patterning between zebrafish and bluefin tuna. Evolution & Development 14: 204–211.

Gilmour D, Knaut H, Maischein H‐M and Nüsslein‐Volhard C (2004) Towing of sensory axons by their migrating target cells in vivo. Nature Neuroscience 7: 491–492.

Gompel N, Dambly‐Chaudière C and Ghysen A (2001) Neuronal differences prefigure somatotopy in the zebrafish lateral line. Development 128: 387–393.

Haas P and Gilmour D (2006) Chemokine signaling mediates self‐organizing tissue migration in the zebrafish lateral line. Developmental Cell 10: 673–680.

Haines L, Neyt C, Gautier P et al. (2004) Met and Hgf signaling controls hypaxial muscle and lateral line development in the zebrafish. Development 131: 4857–4869.

Hammond KL, Loynes HE, Folarin AA, Smith J and Whitfield TT (2003) Hedgehog signalling is required for correct anteroposterior patterning of the zebrafish otic vesicle. Development 130, 1403–1417.

Hammond KL and Whitfield TT (2011) Fgf and Hh signalling act on a symmetrical pre‐pattern to specify anterior and posterior identity in the zebrafish otic placode and vesicle. Development 138: 3977–3987.

Hans S, Liu D and Westerfield M (2004) Pax8 and Pax2a function synergistically in otic specification, downstream of the Foxi1 and Dlx3b transcription factors. Development 131: 5091.

Harding MJ and Nechiporuk AV (2012) Fgfr–Ras‐MAPK signaling is required for apical constriction via apical positioning of Rho‐associated kinase during mechanosensory organ formation. Development 139: 3130–3135.

Harrison RG (1936) Relations of symmetry in the developing ear of Amblystoma punctatum. Proceedings of the National Academy of Sciences of the USA 22: 238.

Itoh M and Chitnis AB (2001) Expression of proneural and neurogenic genes in the zebrafish lateral line primordium correlates with selection of hair cell fate in neuromasts. Mechanisms of Development 102: 263–266.

Kazmierczak P, Sakaguchi H, Tokita J et al. (2007) Cadherin 23 and protocadherin 15 interact to form tip‐link filaments in sensory hair cells. Nature 449: 87–91.

Laguerre L, Ghysen A and Dambly‐Chaudière C (2009) Mitotic patterns in the migrating lateral line cells of zebrafish embryos. Developmental Dynamics 238: 1042–1051.

Lecaudey V, Cakan‐Akdogan G, Norton WHJ and Gilmour D (2008) Dynamic Fgf signaling couples morphogenesis and migration in the zebrafish lateral line primordium. Development 135: 2695–2705.

López‐Schier H and Hudspeth AJ (2006a) A two‐step mechanism underlies the planar polarization of regenerating sensory hair cells. Proceedings of the National Academy of Sciences of the USA 103: 18615–18620.

López‐Schier H, Starr CJ, Kappler JA, Kollmar R and Hudspeth AJ (2004) Directional cell migration establishes the axes of planar polarity in the posterior lateral‐line organ of the zebrafish. Developmental Cell 7: 401–412.

Ma EY and Raible DW (2009) Signaling pathways regulating zebrafish lateral line development. Current Biology 19: R381–R386.

Ma EY, Rubel EW and Raible DW (2008) Notch signaling regulates the extent of hair cell regeneration in the zebrafish lateral line. Journal of Neuroscience 28: 2261–2273.

Mahoney Rogers AA, Zhang J and Shim K (2011) Sprouty1 and Sprouty2 limit both the size of the otic placode and hindbrain Wnt8a by antagonizing FGF signaling. Developmental Biology 353: 94–104.

Matsuda M, Nogare D, Somers K et al. (2013) Lef1 regulates Dusp6 to influence neuromast formation and spacing in the zebrafish posterior lateral line primordium. Development 140: 2387–2397.

McCarroll MN, Lewis ZR, Culbertson MD et al. (2012) Graded levels of Pax2a and Pax8 regulate cell differentiation during sensory placode formation. Development 139: 2740–2750.

McGraw HF, Drerup CM, Culbertson MD et al. (2011) Lef1 is required for progenitor cell identity in the zebrafish lateral line primordium. Development 138: 3921–3930.

Mirkovic I, Pylawka S and Hudspeth AJ (2012) Rearrangements between differentiating hair cells coordinate planar polarity and the establishment of mirror symmetry in lateral‐line neuromasts. Biology Open 1: 498–505.

Nechiporuk A, Linbo T, Poss KD and Raible DW (2006) Specification of epibranchial placodes in zebrafish. Development 134: 611–623.

Nechiporuk A and Raible DW (2008) FGF‐dependent mechanosensory organ patterning in zebrafish. Science 320: 1774–1777.

Ohyama T and Groves AK (2004) Expression of mouse Foxi class genes in early craniofacial development. Developmental Dynamics 231: 640–646.

Ohyama T, Mohamed OA, Taketo MM, Dufort D and Groves AK (2006) Wnt signals mediate a fate decision between otic placode and epidermis. Development 133: 865–875.

Padanad MS and Riley BB (2011) Pax2/8 proteins coordinate sequential induction of otic and epibranchial placodes through differential regulation of foxi1, sox3 and fgf24. Developmental Biology 351: 90–98.

Pujol‐Martí J, Zecca A, Baudoin J‐P et al. (2012) Neuronal birth order identifies a dimorphic sensorineural map. Journal of Neuroscience 32: 2976–2987.

Schuster K, Dambly‐Chaudière C and Ghysen A (2010) Glial cell line‐derived neurotrophic factor defines the path of developing and regenerating axons in the lateral line system of zebrafish. Proceedings of the National Academy of Sciences of the USA 107: 19531–19536.

Shepherd IT, Pietsch J, Elworthy S, Kelsh RN and Raible DW (2004) Roles for GFRalpha1 receptors in zebrafish enteric nervous system development. Development 131: 241–249.

Valdivia LE, Young RM, Hawkins TA et al. (2011) Lef1‐dependent Wnt/β‐catenin signalling drives the proliferative engine that maintains tissue homeostasis during lateral line development. Development 138: 3931–3941.

Vendrell V, Carnicero E, Giraldez F, Alonso MT and Schimmang T (2000) Induction of inner ear fate by FGF3. Development 127: 2011–2019.

Villablanca EJ, Renucci A, Sapède D et al. (2006) Control of cell migration in the zebrafish lateral line: implication of the gene “tumour‐associated calcium signal transducer,” tacstd. Developmental Dynamics 235: 1578–1588.

Wada H, Dambly‐Chaudière C, Kawakami K and Ghysen A (2013) Innervation is required for sense organ development in the lateral line system of adult zebrafish. Proceedings of the National Academy of Sciences of the USA 110: 5659–5664.

Wark AR, Mills MG, Dang L‐H et al. (2012) Genetic architecture of variation in the lateral line sensory system of threespine sticklebacks. G3: Genes, Genomes, and Genetics 2: 1047–1056.

Wark AR and Peichel CL (2010) Lateral line diversity among ecologically divergent threespine stickleback populations. Journal of Experimental Biology 213: 108–117.

Whitfield TT (2002) Zebrafish as a model for hearing and deafness. Journal of Neurobiology 53: 157–171.

Windsor SP, Tan D and Montgomery JC (2008) Swimming kinematics and hydrodynamic imaging in the blind Mexican cave fish (Astyanax fasciatus). Journal of Experimental Biology 211: 2950–2959.

Zelarayan LC, Vendrell V, Alvarez Y et al. (2007) Differential requirements for FGF3, FGF8 and FGF10 during inner ear development. Developmental Biology 308: 379–391.

Further Reading

Aman A and Piotrowski T (2011) Cell–cell signaling interactions coordinate multiple cell behaviors that drive morphogenesis of the lateral line. Cell Adhesion & Migration 5: 499–508.

Chitnis A, Nogares DD and Matsudas M (2012) Building the posterior lateral line system in zebrafish. Developmental Neurobiology 72(3): 234–255.

Ghysen A and Dambly‐Chaudière C (2007) The lateral line microcosmos. Genes & Development 21: 2118–2130.

Gillespie PG and Müller U (2009) Mechanotransduction by hair cells: models, molecules, and mechanisms. Cell 139: 33–44.

Nicolson T (2005) The genetics of hearing and balance in zebrafish. Annual Review of Genetics 39: 9–22.

Nuñez VA, Sarrazin AF, Cubedo N et al. (2009) Postembryonic development of the posterior lateral line in the zebrafish. Evolution & Development 11: 391–404.

Streit A (2004) Early development of the cranial sensory nervous system: from a common field to individual placodes. Developmental Biology 276: 1–15.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Harding, Molly, McCarroll, Matthew, McGraw, Hillary, and Nechiporuk, Alex(Nov 2013) Ear and Lateral Line of Vertebrates: Organisation and Development. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000790.pub3]