Cutaneous respiration
The skin of amphibians is a major site of respiration in all species for which measurements are available. Cutaneous respiration is the sole respiratory mode of lungless salamanders (family Plethodontidae) which lack lungs entirely yet constitute the largest family of salamanders. Cutaneous respiration in frogs and other amphibians may be the primary respiratory mode during colder temperatures.
Orbiting Frog Otolith
The frogs, housed in the centrifuge, are in the liquid loop. Moving from the lung to the frogs, the loop contains water and dissolved oxygen; moving from the frogs back to the lung, it contains water and free CO. A double layer of polyurethane foam lining the interior of the centrifuge prevents frog waste matter from fouling the water circulation system. Water is circulated through the liquid loop using a small pump and must pass through the filter before leaving the centrifuge.