Brainless but not directionless, jellyfish swim against the current

Scientists have found that jellyfish don't always go with the flow (Photo: Shutterstock)

For many people, jellyfish are just an unwelcome addition to a day at the beach. But the gelatinous creatures can seriously affect commercial fishing ventures and even cause the shutdown of power stations when they form into giant "blooms" in the ocean. Researchers at Deakin University in Australia, might be on the way to a solution.

Jellyfish blooms are enormous groupings of the gently floating creatures and their numbers have been on the increase in recent years. The blooms can present serious problems, even though they are necessary for the ecosystem and a good food source for many creatures, such as Leatherback Turtles. In 2013, facing increasing numbers of the creatures, Korea dispatched jellyfish-shredding robots to cut down the population.

It might sound cruel, but the creatures do not have brains or hearts, which is why the discovery by the team was so surprising. They found that jellyfish can not only detect the ocean’s currents, but swim against them. Other much more evolved sea creatures, like turtles, cannot. They may not be the passively floating things of popular imagination.

Professor Graeme Hays, from Deakin and scientists from Swansea University, tracked free-ranging barrel-jellyfish in waters off northern France using GPS loggers equipped with accelerometers that allowed the scientists to observe how the jellyfish orientate their movements with respect to currents. GPS-tracked floats were used to record the local currents. The GPS data showed they were actively swimming counter to the current and the researchers are now asking whether this occurs with other species of jellyfish?

If in fact this "superpower" is possessed by other species, the researchers say it will present a solution to the universal problem of jellyfish blooms. By yetter understanding the blooms it might be possible to predict where and when they will appear, allowing aquaculture farms and others to take protective measures.

"The insights into their behavior and the movements of the ocean helps to explain how jellyfish can form blooms including hundreds to millions of individuals for periods up to several months," said Professor Hays.

It isn’t known how they can "know" how to do this, but it’s possible they could detect current shear or assess the drift using infrasound or the Earth’s magnetic field.

"We now know that jellyfish are not just bags of jelly drifting passively in the oceans," adds Professor Hays. "They are incredibly advanced in their orientation abilities."

There are plans to replicate the work in Tasmania, home to many salmon farms.

The team's research was published in the journal Current Biology

The video below shows one of the jellyfish being tagged.

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