Apart from its visual camouflage tactics, a cuttlefish also holds its breath to hide electrical fields and evade predator sharks, researchers found. Researchers from the Georgia Southern University found that a tiny, squid-like cuttlefish can lower its microvolts by slowing its ventilation.
With their eyes located on the sides of their head, sharks are basically blind facing forward and near the mouths. Sharks compensate by using their snouts to detect electrical fields from preys like the common cuttlefish.
Faint traces of electric current are emitted from a cuttlefish's siphons located on the sides of its head. The small electrical currents emanated from the cuttlefish's metabolic process like breathing. In an experiment conducted by the assistant professor Christine Bedore and her colleagues, they learned that sharks bite when they detect the electrical fields but the common cuttlefish has found a way to evade the deadly predators. Bedore studied the unique phenomenon at Duke University's Sönke Johnsen lab as a post-doctoral researcher.
The researchers documented that a cuttlefish emits up to 30 microvolts, which is 75,000 times lower than an average triple A battery, but still enough to be detected by predators. The cuttlefish can lower the microvolts down to just six microvolts by covering its siphons using its arms, freezing in place and basically slowing its ventilation. This reduces the cuttlefish's bioelectric field by 89 percent.
"The freeze response may also facilitate other non-visual cryptic mechanisms to lower predation risk from a wide range of predator types," wrote the researchers in the Proceedings of the Royal Society B on Dec. 2.
If the freezing technique fails, the cuttlefish can also emit a cloud of black ink and "jet away" using the strong gust from its siphon and mantle. Unfortunately, this increases its electric signal four times higher than its resting signal.
"Jetting would only be for use as a last resort," said Bedore. In the experiments, the test-sharks appeared fond of the ink's taste and the current produced by the cuttlefish's jetting efforts.
Photo: Martin Cathrae | Flickr
