Deep-Diving Sharks

A new study released yesterday revealed a species of hammerhead shark that has evolved to hold its breath for an average of 17 minutes at a time, likely in an effort to preserve body temperature as they make deep dives into colder waters in search of food. It is the first time such an ability has been observed in fish and suggests the animals developed a mechanism to counter a drop in blood-oxygen levels as breathing halts.

Scalloped hammerheads have been known to hunt for prey at ocean depths where the temperature hovers around 40 degrees Fahrenheit. However, given sharks are ectothermic—or cold-blooded, meaning their body temperature is regulated by the surrounding environment (see 101)—it remained a mystery how the animals functioned during extended dives. Researchers say the largest point of heat loss in fish is the gills and may correspond with a slowdown in heat muscle activity.

Learn how hammerhead sharks evolved to possess their distinctive skull shape (w/video).