How do Mysticete (Baleen) Whales Make Two Sounds Simultaneously?

Abstract

Mysticete (baleen) whales use the larynx to generate sounds. Air flowing past the U‐shaped vocal folds causes vibrations that are transferred through overlying throat tissues to water. Sounds can be made repetitively without surfacing for a breath due to air recycling between lungs and larynx. We hypothesize that tissue movements direct airflow between sound generating and air recycling regions of the larynx. Methods involved examination of twenty mysticete specimens found beached along the northeast US coastline. Larynges were recovered post mortem from carcasses of minke (Balaenoptera acutorostrata), fin (B. physalus), sei (B. borealis), blue (B. musculus), humpback (Megaptera novaeangliae), and right (Eubalaena glacialis) whales. All specimens were collected under the auspices of the Marine Mammal Health and Stranding Response Program, and possession was permitted via a letter of authorization from NOAA‐NMFS. Results show that the larynx has two valves. One valve is located between the vocal folds. This valve is aided by a newly discovered cushion of tissue on the ventral surface of the cricoid cartilage. It appears to function like a plug, apparently hermetically sealing the gap between the vocal folds. Air flowing around this interlock is channeled superiorly between the corniculate cartilages. A second valve is found between the paired corniculate cartilages. Closure is aided by raising the epiglottis to plug the gap between the corniculates. This seals the rostral larynx, preventing air from escaping towards the nose. Air is instead diverted ventrally between the vocal folds and into the laryngeal sac. These two valves direct airflow towards vocal folds or corniculate flaps. Flow between the vocal folds may generate song, and allow extended vocalizations as air is captured and recycled between the laryngeal sac and the lungs. Flow between the corniculate flaps may generate pulses, but these sounds would continue only until the nasal region becomes pressurized.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.