Barn owl auditory thresholds from Barn owls have ageless ears

Auditory thresholds from barn owls of different age group

Prediction of basilar-papilla frequency map derived from hair-bundle morphology.

<p>A–C: Known frequency representations along the basilar papilla of the emu (A), chicken (B) and barn owl (C) compared to the variation in morphological factor (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#s4" target="_blank">Methods</a>). Frequency maps were plotted using the equations of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Kppl3" target="_blank">[14]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Chen1" target="_blank">[63]</a> and an improved polynomial fit to the data of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Kppl2" target="_blank">[13]</a>; they are shown in black, referring to the right ordinates. Stereovillar height and number for neurally-located hair cells were taken from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Fischer1" target="_blank">[7]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Manley2" target="_blank">[11]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Kppl1" target="_blank">[12]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Tilney2" target="_blank">[64]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Fischer2" target="_blank">[65]</a> and the morphological factor derived from those is shown in gray, referring to the left ordinates. Note that the morphological factor correlates well with the species-specific shape of the frequency maps. D: Morphological factor and a prediction for the frequency distribution in the kiwi. The prediction is based on a linear regression of frequency as a function of morphological factor for the pooled data from emu (circles), chicken (triangles) and barn owl (diamonds), shown in the inset.</p

Overview of the kiwi basilar papilla.

<p>A: Surface view of the basilar papilla obtained from scanning electron microscopy. The tiny white dots represent individual hair-cell bundles. B: Cross section of the kiwi cochlea approximately half way along the basilar papilla. Key structures are labelled.</p

Number of stereovilli in mechanosensory hair-cell bundles increased nearly linearly along the basilar papilla.

<p>A, B: Two examples of SEM micrographs of hair bundles located at 10% from the apical end, neurally (A) and at 90%, abneurally (B). C: Boxplot of stereovillar numbers as a function of papillar position. For each longitudinal position, 3 different values are shown for hair cells located at the neural edge, near the midline and at the abneural edge, respectively.</p

Spectrograms of typical male and female kiwi vocalisations.

<p>The entire calls are shown to the left and an enlargement of one component of the calls with a power slice of the area indicated by the yellow line to the right. For details regarding recording and analysis methods see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023771#pone.0023771-Corfield2" target="_blank">[54]</a>. Briefly, spectrograms and power spectra were produced with a Fast Fourier Transformation (FFT) size of 1,024 points using a Hamming window and 50% overlap, which produced a frequency resolution of 56 Hz.</p