Abstract
ABSTRACTThe vertebrate inner ear contains vestibular receptors with dense crystals of calcium carbonate, the otoconia. The production and maintenance of otoconia is a delicate process, the perturbation of which can lead to severe vestibular dysfunction in humans. The details of these processes are not well understood. Here, we report the discovery of a new otoconial mass in the lagena of adult pigeons that was present in more than 70% of birds. Based on histological, tomographic and elemental analyses, we conclude that the structure likely represents an ectopically-formed otoconial assembly. Given its frequent natural occurrence, we suggest that the pigeon lagena is a valuable model system for investigating misregulated otoconial formation.This article has an associated First Person interview with the first author of the paper.
Highlights
The inner ear of vertebrates contains several sensory epithelia that enable the detection of sound, acceleration and gravity
As part of an ongoing study to investigate the anatomical and elemental features of the avian cochlear duct, we observed a small, spherical, otoconial structure at the junction between the lagena and basilar papilla, close to the dorsal epithelium (Fig. 1C,F,I). This structure appeared to be attached to the tegmentum vasculosum and the transitional epithelium. We observed this otoconial mass in 72% of cochlear ducts from adult (>1 year of age) pigeons (n=39 ears, n=23 pigeons, Fig. 1J)
The crystal structure of the otoconia appeared to be finer-grained compared to regular lagenar otoconia
Summary
The inner ear of vertebrates contains several sensory epithelia that enable the detection of sound, acceleration and gravity. The basilar papilla (equivalent to the mammalian organ of Corti) is responsible for hearing, the semicircular canals perceive rotational acceleration, and the sacculus and utriculus detect linear acceleration (Manley, 1990). The latter two organs, together with an additional inner ear organ called the lagena, contain dense aggregates of proteins and calcium carbonate (CaCO3) crystals called otoconia. Otoconia are formed during embryonic development and maintained during adulthood (Ross, 1979; Thalmann et al, 2001) They are embedded within a gelatinous matrix, the otolithic membrane, lying above sensory hair cells. Relative movement of these otoconia result in the application of force on the stereocilia of the underlying hair cells, facilitating mechanotransduction
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