Respiration of crabs in air and water

Abstract

1. 1. Oxygen consumption (.VO 2), ventilation volume (.V) and O 2 extraction (Ext) were measured for three species of crabs: the terrestrial Gecarcinus lateralis, the amphibious Cardisoma guanhumi, and the aquatic Callinectes sapidus. In air the .V O 2 of the crabs was ranked Gecarcinus > Cardisoma > Callinectes. In water the .V O 2 was Callinectes > Cardisoma > Gecarcinus. 2. 2. When terrestrial Gecarcinus was submerged in water, .V O 2 fell to 1 7 of its aerial value because both .V and Ext fell. When aquatic Callinectes was exposed to air, .V O 2 fell to 1 3 of its aquatic value because both .V and Ext fell. Only the amphibious Cardisoma maintained .V O 2 constant in both media; in water .V was increased to offset a fall in Ext. 3. 3. All species behaved as .V O 2 , conformers when they were exposed to short-term hypoxia; the effect was more pronounced in the aquatic environment. 4. 4. Severe short-term hypercapnia caused no change in the aquatic environment; but it stimulated increased .V and decreased Ext in air. 5. 5. Such effects are consistent with vertebrate responses: O 2 seems to be the most important regulatory factor of respiration in water and CO 2 is the most important in air.