Animal Behavior

Jellyfish are not just drifters ...

"They are incredibly advanced in their orientation abilities," scientists report in Current Biology

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A barrel jellyfish (Credit: Graeme Hays, PhD)Jellyfish might look like mere drifters, but some of them have a remarkable ability to detect the direction of ocean currents and to swim strongly against them, according to new evidence in free-ranging barrel-jellyfish reported today in the Cell Press journal Current Biology.

"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," said Dr. Graeme Hays, Professor and Chair of Marine Sciences at Deakin University in Australia.

"Jellyfish are not just bags of jelly drifting passively in the oceans," he added. "They are incredibly advanced in their orientation abilities."

The researchers tracked the movements of the jellyfish with GPS loggers and used GPS-tracked floats to record the current flows. They also directly observed the swimming direction of large numbers of jellyfish at the surface of the ocean.

The data show that jellyfish can actively swim at counter-current in response to drift, the researchers report. Their model of the jellyfishes' behavior, together with ocean currents, helps to explain how jellyfish are able to form blooms including hundreds to millions of individuals for periods up to several months.

[pullquote align="right"]"Jellyfish are not just bags of jelly drifting passively in the oceans. They are incredibly advanced in their orientation abilities." — Graeme Hays, PhD, Professor and Chair of Marine Sciences at Deakin University[/pullquote]

It's not yet clear exactly how the jellyfish figure out which way to go. Dr. Hays and co-author Dr. Sabrina Fossette of the Swansea Lab for Animal Movement in the UK said it's possible that the animals detect current shear across their body surface, or they may indirectly assess the direction of drift using other cues, such as the Earth's magnetic field or infrasound.

Understanding the distribution of jellyfish in the open ocean may be practically useful for predicting and avoiding troublesome jellyfish blooms, especially if it turns out that the findings in barrel-jellyfish apply to other species. While jellyfish do play an important role in ocean ecosystems as prey for leatherback sea turtles and other animals, Hays notes, they can also clog fishing nets and sting beachgoers.

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

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Watch a tagged jellyfish in motion

This video, by Current Biology author Dr. Graeme Hays, shows how jellyfish swim against the current.

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Read the article

Cell Press has made this article freely available until February 5, 2015:

Current Biology, Fossette et al: "Current-oriented swimming by jellyfish and its role in bloom maintenance"

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Current Biology, published by Elsevier's Cell Press, is a bimonthly journal that features papers in any area of biology that have sufficient claim to be of general interest. A primary aim of the journal is to foster communication across fields of biology, both by publishing important findings of general interest from diverse fields and through highly accessible editorial articles that explicitly aim to inform non-specialists.

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Elsevier Connect Contributor

Joseph CaputoJoseph Caputo (@sciencemetro) is Media Relations Manager for Cell Press (@CellPressNews), based in Cambridge, Massachusetts. He previously served as a science communicator for the Harvard Stem Cell Institute, the Marine Biological Laboratory and Smithsonian Magazine. As Media Relations Manager, he works closely with the media and public information officers to share the scientific breakthroughs published in Cell Press's 31 journals. He is a graduate of Sarah Lawrence College in New York and received his MS in Science and Medical Journalism from Boston University.

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