Breathing Gas Mixtures Different from Air: An Adaptation for Survival Under the Ice of a Facultative Air-Breathing Fish
JOHN J. MAGNUSON 1,
JOHN W. KELLER 1,
ANNAMARIE L. BECKEL 1, and
GEORGE W. GALLEPP 1
1 Center for Limnology and Department of Zoology, University of Wisconsin, Madison 53706
Gaseous respiration by central mudminnows (Umbra limi), particularly their use of bubbles composed of gas mixtures other than air, may have evolved as an adaptation to the oxygen-depleted, carbon dioxide-rich water of winterkill lakes. Under simulated winterkill conditions, mudminnows frequently engulfed gaseous bubbles. Use of bubbles was not related to varying methane or nitrogen content (0 to 80 percent) when all bubbles contained 20 percent oxygen. When the oxygen content of bubbles varied (0 to 20 percent), fish visited bubbles randomly but remained longer and took fewer "breaths" at bubbles with high oxygen content. High temperature (16° to 34°C) and low pH (6.8 to 4.5) did not stimulate increased air-breathing when dissolved oxygen was sufficient.
Submitted on August 2, 1982
Revised on December 6, 1982
