- 1.
Changes in the configuration of the fowl syrinx during experimental stimulation of the extrinsic syringeal muscles were assessed by monitoring simultaneous changes in the airway resistance at a constant airflow rate.
- 2.
Stimulation of the caudal part of the tracheolateralis muscle produced a change away from the sound-producing configuration. The tympanum was drawn craniad, the external tympaniform membranes were stretched and airway resistance fell as the syringeal lumen enlarged.
- 3.
Stimulation of the sternotrachealis muscles produced a change towards the sound-producing configuration. The tympanum was drawn caudad, the membranes relaxed and airway resistance rose due to the constriction of the syringeal lumen.
- 4.
Tetanic stimulation of the cranial parts of both tracheolateralis and tracheohyoideus produced a marked retraction of the larynx and rostral part of the trachea.
- 5.
The threshold levels of air-sac pressure and airflow rate necessary to produce sound by passive ventilation of the respiratory system were monitored. Passive sound could be abolished either by stimulating the tracheolateralis muscle or by marginally increasing the tracheal resistance, simulating glottal constriction.
- 6.
Results are discussed in relation to current opinions on the importance of active and passive factors during vocalization in birds. It is concluded that the involvement of the extrinsic muscles may be necessary when producing low volume sounds by relatively weak physical effort. Passive factors appear to be more important during vigorous calling, such as crowing. In the latter case the main function of the extrinsic muscles may be to ensure the retraction of the larynx and changes in shape of the anterior respiratory tract.
In the field: an interview with Sönke Johnsen
(update2)-SonkeJohnsen.jpg?versionId=3990)
Sönke Johnsen is a Professor at Duke University, USA, investigating visual ecology and he talks about his experiences of collecting transparent animals while blue water diving and in a submersible, as well as outrunning Hurricane Katrina.
Call for new preLighters
(update)-CallForPreLighters.png?versionId=3990)
preLights is the preprint highlighting community supported by The Company of Biologists. At the heart of preLights are our preLighters: early-career researchers who select and write about interesting new preprints for the research community. We are currently looking for new preLighters to join our team. Find out more and apply here.
Graham Scott in conversation with Big Biology
Graham Scott talks to Big Biology about the oxygen cascade in mice living on mountaintops, extreme environments for such small organisms. In this JEB-sponsored episode, they discuss the concept of symmorphosis and the evolution of the oxygen cascade.
Trap-jaw ants coordinate tendon and exoskeleton for perfect mandible arc
-AntJaws.png?versionId=3990)
Trap-jaw ants run the risk of tearing themselves apart when they fire off their mandibles, but Greg Sutton & co have discovered that the ants simultaneously push and pull the mandibles using energy stored in a head tendon and their exoskeleton to drive the jaws in a perfect arc.
Hearing without a tympanic ear
-Review.png?versionId=3990)
In their Review, Grace Capshaw, Jakob Christensen-Dalsgaard and Catherine Carr explore the mechanisms of hearing in extant atympanate vertebrates and the implications for the early evolution of tympanate hearing.
Social media
