Morphology and innervation of the vestibular lagena in pigeons

Abstract

The morphological characteristics of the pigeon lagena were examined using histology, scanning electron microscopy, and biotinylated dextran amine (BDA) neural tracers. The lagena epithelium was observed to lie partially in a parasagittal plane, but was also U-shaped with orthogonal (lateral) directed tips. Hair cell planar polarities were oriented away from a central reversal line that ran nearly the length of the epithelium. Similar to the vertebrate utricle and saccule, three afferent classes were observed based upon their terminal innervation pattern, which include calyx, dimorph, and bouton fibers. Calyx and dimorph afferents innervated the striola region of the lagena, while bouton afferents innervated the extrastriola and a small region of the central striola known as the type II band. Calyx units had large calyceal terminal structures that innervated only type I hair cells. Dimorph afferents innervated both type I and II hair cells, with calyx and bouton terminals. Bouton afferents had the largest most complex innervation patterns and the greatest terminal areas contacting many hair cells.

Magnetic field-driven induction of ZENK in the trigeminal system of pigeons ( Columba livia )

“…However, the exact mechanisms how the Earth's magnetic field is perceived and processed is only starting to be understood. Currently, three main magnetoreception hypotheses are discussed: a light-dependent chemical compass sense associated with the visual system [3][4][5][6][7][8][9][10], a recently suggested involvement of the vestibular system [11][12][13][14][15] but see [16], and an iron-mineral-based sense located in the upper beak [17][18][19][20]. The last hypothesis was associated with claims of the existence of iron-mineral structures in six defined dendritic fields within the subepidermal layer of the upper beak [17][18][19][20].…”

A role for the otoliths in the mechanics of cochlear homeostasis?

“…The basic shape of the lagena is taken from curve fits of the morphology [18] redrawn in Fig.1A. Hair cells external to the socalled line-of-reversal (green dashed line) are oriented towards the longer rim (pars externa), and vice versa.…”

Magnetoreception and baroreception in birds

“…It is one of three otolithic sense organs in the inner ear and detects linear accelerations (Zakir et al . ). Following on from the observation that the lagena contains iron‐rich otoliths (Harada et al .…”

“…The lagena is a vestibular sense organ located at the distal tip of the basilar papilla; it is present in birds, but absent in mammals. It is one of three otolithic sense organs in the inner ear and detects linear accelerations (Zakir et al 2012). Following on from the observation that the lagena contains iron-rich otoliths (Harada et al 2001), behavioral experiments demonstrated that lagena removal, or the insertion of small magnets into the inner ear, compromised the navigational abilities of homing pigeons (Harada 2002).…”