During the last 3000 years, man and the tuna have had a close association;many early civilisations based around the Mediterranean Sea trapped the fish as part of their diets. More recently, man's attention has been caught by the tunas' extraordinary physiology, which allows them to exploit environmental niches closed to other fish. In a Commentary published in this issue of the JEB, Jeffrey Graham and Kathryn Dickson explain that `comparative physiologists seek to understand the mechanism and biological significance of physiological adaptation, and tunas satisfy all criteria essential for this'(p. 4015).
Describing the tunas' unique swimming style and body shape, Graham and Dickson also explain many advantages of this group's ability to retain body heat through countercurrent heat exchange tissue, retia mirabila, which help to maintain the fish's extreme performance levels even when venturing into icy northern waters. The team also discuss the fish's elevated aerobic scope and standard metabolic rate, which coupled with their specialised oxygen transport system allow them to achieve levels of performance beyond the physiological capacities of other fish.
But while many questions about tuna physiology have recently been resolved,many remain outstanding, and will continue to intrigue comparative physiologists for decades to come.