Morphogenesis of the inner ear of Rana temporaria (Amphibia,Anura)

Summary Differentiation of the inner ear of Rana temporaria temporaria Linné, 1758 begins with invagination of the epidermis to form the otocyst. The first sensory epithelium to form is the macula communis. Not until this is complete are the semicircular canals produced as protrusions from the otocyst; at the same time the ampullar cristae develop as structures for the detection of rotation, separate from the macula communis. The formation of utricle and saccule, organs for the gravitational sense, occurs by concentric constriction between the superior and inferior parts of the otocyst, dividing the macula communis into two parts. At a time when the utricle and the semicircular canals have completely differentiated, the saccule region of the inner ear is still undergoing morphological development, with the formation first of the two auditory papillae (the basilar and amphibian papillae) and then of the lagena, an evagination of the saccule.Abbreviations aa Anterior ampulla - al Lateral ampulla - c Cartilage - ca Ampullar crista - cc Crus commune - csa Anterior semicircular canal - csl Lateral semicircular canal - csp Posterior semicircular canal - cu Cupula - ed Epidermis - fus Utriculo-saccular foramen - g Ganglion - kc Kinocilium - l Lagena - m Medulla oblongata - mc Macula communis - mes Mesenchyme - ms Macula of the saccule - mu Macula of the utricle - on Organic network - pa Amphibian papilla - pb Basilar papilla - pi Inferior part of otocyst - pm Presumptive medulla oblongata - po Preotolith - ps Superior part of otocyst - raa Anterior acoustic ramus - rl Recess of labyrinth - s Saccule - tm Tectorial membrane - u Utricle - * Perilymphatic space