Basilar papilla of the canary and zebra finch: A quantitative scanning electron microscopical description

Abstract

Morphological parameters of the apical surface of canary and zebra finch basilar papillae were quantitatively evaluated by scanning electron microscopy. The papillar length is -1.6 mm in both species. The zebra-finch papilla has a larger number of hair cells and is wider in the apical half of the papilla as compared to the canary. These two small songbird species have the smallest number of hair cells and the smallest papillae of the bird species investigated to date. The orientation of the hair cells is much more homogenous as compared to other species. Also, the discrepancy in the number of stereovilli of neural and abneural hair cells is much larger than in other bird species. A detailed analysis of gradients across the papilla in the canary revealed that anatomical parameters change in the neural half, whereas they remain rather constant in the abneural half of the papilla. There were, however, no obvious borders that separated distinct hair cell populations in either species. o

Inner-Ear Morphology of the New Zealand Kiwi (Apteryx mantelli) Suggests High-Frequency Specialization

“…The orientation of the stereovillar bundles in kiwi shows a pattern similar to that in most other birds (Fischer et al 1988;Gleich and Manley 1988;Gleich et al 1994;Köppl et al 1998;Manley et al 1993Manley et al , 1996Tilney et al 1987). Hair cells at both the neural and abneural edges of the papilla all have their bundles oriented nearly perpendicular to the edge, i.e., radially across the papilla, with bundles towards the papillar midline increasingly orientated towards the apex.…”

“…It is therefore likely that, as in the emu (Köppl 2001), the great majority of efferent fibers are unmyelinated axons of too small a diameter to be resolved light-microscopically. Assuming~8,185 afferent fibers for the kiwi, this number is low compared to that reported in other species (barn owl (T. alba): 32,500, chicken (G. gallus): 14,250, emu (D. novaehollandiae): 11,220, starling (S. vulgaris): 10,120, duck (A. fuligula): 11,000, budgerigar (Melopsittacus undulates): 10,890 canary (S. canaria): 6,880), with only the canary containing fewer fibers Gleich et al 1994;Köppl 1997;Köppl et al 2000). Subtracting the number of lagenar fibers from the total number of afferent fibers gave an estimate of 6,936 auditory afferent fibers in the kiwi.…”

“…The morphology of the BP and associated hair cells has been evaluated in detail in a number of avian species, ranging from those that have high or low frequency hearing, and those that are auditory generalists or specialists (chicken, Gallus gallus (Manley et al 1996;Tilney and Saunders 1983), seagull, Larus marinus (Counter and Tsao 1986), starling, Sturnus vulgaris and pigeon, Columba livia (Gleich and Manley 1988), barn owl, Tyto alba (Fischer et al 1988), rhea, Rhea americana (Jorgensen and Christensen 1989), budgerigar, Melopsittacus undulatus , canary, Serinus canaria and zebra finch, Taeniopygia guttata (Gleich et al 1994), duck, Aythya fuligula (Manley et al 1996), and emu, Dromaius novaehollandiae (Köppl et al 1998)). Kiwi are unique in that they appear to be a high frequency specialist (Corfield et al 2011), like barn owls, despite belonging to an ancestral group of birds, the Paleognathae.…”

Inner-ear abnormalities and their functional consequences in Belgian Waterslager canaries (Serinus canarius)

“…tall and short hair cells) are affected differently. In the canary basilar papilla many morphological parameters vary between the neural and the abneural edges, however, an unequivocal distinction between tall and short hair cells is not possible on the basis of a SEM analysis of the papillar surface (Gleich et al, 1994). Nevertheless we can compare the degree of abnormalities found in neural and abneural hair cells.…”

The sender-receiver matching hypothesis: support from the peripheral coding of acoustic features in songbirds

“…ABR latency in birds is shortest at the best frequencies (typically 2-4kHz) and increases above and below these frequencies, and is thought to be predominantly a result of frequency-specific synaptic integration time (Henry and Lucas, 2008). The cochlea of the bird is also arranged tonotopically (Gleich et al, 1994;Gleich and Manley, 2000), so latency shifts are expected to be continuous as you move away from the best frequency. Away from best frequency, spectral splatter could result in latency shifts by activating cochlear partitions with short latencies; however, whether that cochlear partition is above or below the stimulus frequency will be dependent on the location of the stimulus frequency relative to the best excitatory frequency.…”