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Functional Morphology and Symmetry in the Odontocete Ear Complex
William Ary1, Ted W Cranford2, Annalisa Berta3
1Department of Biology, San Diego State University, 2674 Russmar Drive, San Diego, CA, 92123-3422, USA. williamjamesary@gmail.com.
Advances in Experimental Medicine and Biology
|November 28, 2015
Summary
Dolphin ear bones (tympanoperiotic complexes) showed slight asymmetry between left and right sides. This contrasts with the more pronounced asymmetry found in the nasal regions of toothed whales (odontocetes).
Area of Science:
- Comparative Anatomy
- Bioacoustics
- Marine Mammal Biology
Background:
- Odontocete (toothed whale) skulls exhibit directional asymmetry, particularly in the nasal region, which is crucial for echolocation.
- The tympanoperiotic complex (TPC), the bone housing the cetacean ear, plays a vital role in auditory processing and sound reception.
- Understanding asymmetry in TPCs is important for insights into auditory function and evolutionary adaptations in marine mammals.
Purpose of the Study:
- To investigate and quantify the degree of asymmetry in the tympanoperiotic complexes (TPCs) of two odontocete species.
- To compare the asymmetry of TPCs with known asymmetry in the nasal region of odontocetes.
- To assess the potential impact of TPC asymmetry on auditory perception and echolocation capabilities.
Main Methods:
- Acquisition of left and right TPCs from a long-beaked common dolphin (Delphinus capensis) and an Amazon River dolphin (Inia geoffrensis).
- Volumetric analysis comparing the volumes of left and right TPCs within each specimen.
- 3D model superimposition comparing mirrored left TPCs to right TPCs.
- Vibrational analysis to calculate and compare resonant frequencies of the TPCs using Kolmogorov-Smirnov tests.
Main Results:
- All analyses revealed slight volumetric and visual differences between the left and right TPCs within individual dolphins.
- Resonant frequency comparisons also indicated minor variations between the paired TPCs.
- The observed asymmetry in TPCs was notably less pronounced than the established directional asymmetry in the odontocete nasal region.
Conclusions:
- The tympanoperiotic complexes (TPCs) of the studied dolphins exhibit slight bilateral asymmetry.
- This asymmetry is less significant compared to the well-documented nasal asymmetry in odontocetes.
- Further research is needed to determine the functional implications of subtle TPC asymmetry on hearing and echolocation in toothed whales.
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