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Jellyfish Do More than Drift

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Jellyfish might look like they are just drifting along with the ocean currents, but according to a new study of barrel jellies, these animals are moving with purpose.

Researchers have found that jellyfish can detect ocean currents and actively swim against them. “Jellyfish are not just bags of jelly drifting passively in the oceans,” says Graeme Hays of Deakin University in Australia. “They are incredibly advanced in their orientation abilities.” It is believed that this is how jellyfish are able to congregate in blooms consisting of hundreds to millions of individuals at certain times of the year.

Scientists have long wondered how jellies are able to navigate the open ocean without eyes, and it seems now they have an answer. “Detecting ocean currents without fixed visual reference points is thought to be close to impossible and is not seen, for example, in lots of migrating vertebrates including birds and turtles,” Hays explains.

Researchers tracked the migrations of jellies with GPS loggers and used GPS-tracked floats to record the current flows. However, exactly how the jellyfish figure out which way to go is not yet fully understood. Researchers believe it’s possible that the surface of the jellyfish’s body is sensitive enough to detect currents. Alternatively, or additionally, they may be using other cues, such as the Earth’s magnetic field or infrasound.

While jellyfish play an important role in ocean ecosystems as prey (for leatherback sea turtles, for example), they can also clog fishing nets and sting beach goers. Understanding how jellyfish navigate in the open ocean and will help oceanographers better predict when and where large numbers of the animals are likely to cause problems.

“Now that we have shown this remarkable behavior by one species, we need to see how broadly it applies to other species of jellyfish,” Hays says. “This will allow improved management of jellyfish blooms.”

These findings are reported in the Cell Press journal Current Biology.

Jellyfish Fun Facts

  • The sting of a jellyfish comes from specialized skin cells in its tentacles called cnidocytes, literally translated as “nettle-jars.”
  • Jellyfish make up about 40% of the total biomass in the ocean.
  • The Irish name for jellyfish is smugairle róin which means “seal’s snot.”

Fun facts from QI

Video and photo courtesy of Graeme Hays

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