title: The frog inner ear: picture perfect?
abstract: Many recent accounts of the frog peripheral auditory system have reproduced Wever's (1973) schematic cross-section of the ear of a leopard frog. We sought to investigate to what extent this diagram is an accurate and representative depiction of the anuran inner ear, using three-dimensional reconstructions made from serial sections of Rana pipiens, Eleutherodactylus limbatus and Xenopus laevis. In Rana, three discrete contact membranes were found to separate the posterior otic (=endolymphatic) labyrinth from the periotic (=perilymphatic) system: those of the amphibian and basilar recesses and the contact membrane of the saccule. The amphibian 'tegmentum vasculosum' was distinguishable as a thickened epithelial lining within a posterior recess of the superior saccular chamber. These features were also identified in Eleutherodactylus, but in this tiny frog the relative proportions of the semicircular canals and saccule resemble those of ranid tadpoles. There appeared to be a complete fluid pathway between the right and left periotic labyrinths in this species, crossing the cranial cavity. Xenopus lacks a tegmentum vasculosum and a contact membrane of the saccule; the Xenopus ear is further distinguished by a lateral passage separating stapes from periotic cistern and a more direct connection between periotic cistern and basilar recess. The basilar and lagenar recesses are conjoined in this species. Wever's diagram of the inner ear of Rana retains its value for diagrammatic purposes, but it is not anatomically accurate or representative of all frogs. Although Wever identified the contact membrane of the saccule, most recent studies of frog inner ear anatomy have overlooked both this and the amphibian tegmentum vasculosum. These structures deserve further attention.
authors: Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK, mjm68@cam.ac.uk.
authors: Matthew J
authors: MJ
authors: Mason
authors: Johannes M
authors: JM
authors: Segenhout
authors: Ariadna
authors: A
authors: Cobo-Cuan
authors: Patricia M
authors: PM
authors: Quiñones
authors: Pim
authors: P
authors: van Dijk
mesh_terms: D000818:Animals; D001001:Anura / Q000033:anatomy & histology*; D007758:Ear, Inner / Q000033:anatomy & histology*; D007091:Image Processing, Computer-Assisted; D011894:Rana pipiens / Q000033:anatomy & histology*; D014982:Xenopus laevis / Q000033:anatomy & histology*
references: IEEE Trans Image Process. 1998;7(1):27-41
references: 18267377
references: Scan Electron Microsc. 1984;(Pt 4):1899-913
references: 6523060
references: Arch Otorhinolaryngol. 1978 Mar 3;220(1-2):89-103
references: 306247
references: J Morphol. 1973 Dec;141(4):461-77
references: 4543394
references: Mol Phylogenet Evol. 2007 Feb;42(2):331-8
references: 16997582
references: Hear Res. 2011 Mar;273(1-2):46-58
references: 20149854
references: Hear Res. 2002 Feb;164(1-2):155-65
references: 11950535
references: Mol Biol Evol. 2004 Jul;21(7):1188-200
references: 14963093
references: Hear Res. 1984 Mar;13(3):261-8
references: 6330016
references: J Exp Biol. 2002 Oct;205(Pt 20):3153-65
references: 12235195
references: J Comp Physiol A. 1998 Jan;182(1):59-64
references: 9447714
references: Proc Inst Acoust. 2009 Jan 1;31:13-21
references: 20953303
references: Hear Res. 2003 Jan;175(1-2):54-65
references: 12527125
references: Dev Dyn. 2003 Jul;227(3):422-30
references: 12815629
references: Mol Phylogenet Evol. 2007 Feb;42(2):317-30
references: 16949307
references: Proc Natl Acad Sci U S A. 1978 Jan;75(1):529-30
references: 272671
references: J Physiol. 1986 Feb;371:17-28
references: 3486270
references: Brain Behav Evol. 1976;13(2-3):196-215
references: 1086699
references: J Comp Physiol A. 2000 May;186(5):489-95
references: 10879951
references: J Comp Physiol A. 2000 May;186(5):481-8
references: 10879950