Root cause of fish buoyancy

摘要

Fish have a problem — because their body tissues are denser than water they have a tendency to sink. Those that have solved the problem with a swim bladder face the complication that, to retain neutral buoyancy, they must secrete gas into the bladder against a pressure gradient; the deeper they swim, the bigger the gradient. A study by Mylvaganam et al., published in the March issue of Nature Structural Biology, in part reveals how they do it. The authors show that certain fish haemoglobins have structural characteristics that make them efficient proton-driven oxygen pumps, able to drive the gas into a swim bladder.