Discovery of a low frequency sound source in mysticeti (Baleen Whales) : Anatomical establishment of a vocal fold homolog

摘要: The mechanism of mysticete (baleen whale) vocalization has remained a mystery. Vocal folds (true vocal "cords"), the structures responsible for sound production in terrestrial mammals, were thought to be absent whales. This study tests hypothesis that larynx possesses homologous and they are capable generation. Laryngeal anatomy was examined 37 specimens representing 6 species. Results indicate presence U-shaped fold (U-fold) lumen larynx. U-fold is supported by arytenoid cartilages, controlled skeletal muscles innervated recurrent laryngeal nerve, adjacent diverticulum (laryngeal sac) covered with mucosa superior contains ligament-conditions also define mammals and, therefore, supports homology. Unlike which perpendicular airflow, oriented parallel airflow. adduction/abduction elevation/depression may control vibration its edges generate sounds. walls sac can expand contract, serve as resonant space, propagate vibrations generated movements supporting cartilages. extensive musculature surrounding enable rapid forceful expulsion air from into other respiratory spaces, or maintain constant volume despite effects ambient pressure (e.g., changes during diving ascent). size complexity indicates an organ multiple functions, including protection breathing/swallowing, regulation airflow pressures homolog offers new insight both generation mysticetes divergent evolution odontocete cetaceans.