Buccal pumping (/ˈbʌk.əl/...) is "breathing with one's cheeks": a method of ventilation used in respiration in which the animal moves the floor of its mouth in a rhythmic manner that is externally apparent.[Brainerd, E. L. (1999). New perspectives on the evolution of lung ventilation mechanisms in vertebrates. Experimental Biology Online 4, 11-28. http://www.brown.edu/Departments/EEB/brainerd_lab/pdf/Brainerd-1999-EBO.pdf] It is the sole means of inflating the lungs in .
There are two methods of buccal pumping, defined by the number of movements of the floor of the mouth needed to complete both inspiration and expiration.
Four stroke
Four-stroke buccal pumping is used by some basal ray-finned fish and aquatic amphibians such as
Xenopus and
Amphiuma.
This method has several stages. These will be described for an animal starting with lungs in a deflated state: First, the
glottis (opening to the
) is closed, and the
are opened. The floor of the mouth is then depressed (lowered), drawing air in. The nostrils are then closed, the glottis opened, and the floor of mouth raised, forcing the air into the lungs for gas exchange. To deflate the lungs, the process is reversed.
Two stroke
Two-stroke buccal pumping completes the process more quickly, as is seen in most extant amphibians.
In this method, the floor of the mouth is lowered, drawing air from both the outside and lungs into the buccal cavity. When the floor of the mouth is raised, the air is pushed out and into the lungs; the amount of mixing is generally small, about 20%.
Gular pumping
Gular pumping refers to the same process, but accomplished by expanding and contracting the entire throat to pump air, rather than just relying upon the mouth.
This method of ventilation is inefficient, but is nonetheless used by all air-breathing and gular pumping is utilized to a varying extent by various reptile species.
See also
-
Carrier's constraint
-
Circular breathing
