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January 22, 2015

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Jellyfish not just drifters, study finds

Jan. 22, 2015
Courtesy of Cell Press
and World Science staff

It may seem hard to think of a more soulless-looking an­i­mal than a jel­ly­fish—but these crit­ters may be more will­ful than we give them cred­it for, a study finds.

Ac­cord­ing to the re­search, at least some jel­ly­fish can swim strongly against a cur­rent, though they may seem to be just drift­ing idly.

“They are in­credibly ad­vanced in their ori­enta­t­ion abil­i­ties,” said Graeme Hays of Dea­kin Uni­vers­ity in Aus­tral­ia, one of the in­ves­ti­ga­tors. They’re “not just bags of jelly drift­ing pas­sive­ly.”

The study looked at free-ranging barrel-jel­ly­fish and is re­ported in the jour­nal Cur­rent Bi­ol­o­gy on Jan­u­ary 22.

The re­search­ers tracked the move­ments of the jel­ly­fish with GPS log­gers and used GPS-tracked floats to rec­ord the cur­rent flows. They al­so watched the swim­ming di­rec­tion of many jel­ly­fish at the sur­face.

The da­ta show that jel­ly­fish can ac­tively swim at counter-cur­rent in re­sponse to drift, the re­search­ers re­port. They add that 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.

It’s not yet clear ex­actly how the jel­ly­fish fig­ure out which way to go. The sci­en­tists say the an­i­mals might de­tect cur­rent across their body sur­face, or might 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 use­ful for pre­dict­ing and avoid­ing trou­ble­some jel­ly­fish blooms, the re­search­ers added. 

While jel­ly­fish 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,” Hays said. “This will al­low im­proved man­age­ment of jel­ly­fish blooms.”


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It may seem hard to think of a more soulless-looking animal than a jellyfish—but these critters may be more willful than we give them credit for, a study finds. According to the research, at least some jellyfish can swim strongly against a current, though they may seem to be just drifting idly. “They are incredibly advanced in their orientation abilities,” said Graeme Hays of Deakin University in Australia, one of the investigators. They’re “not just bags of jelly drifting passively.” 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 in the Cell Press journal Current Biology on January 22. The researchers tracked the movements of the jellyfish with GPS loggers and used GPS-tracked floats to record the current flows. They also watched the swimming direction of many jellyfish at the surface. The data show that jellyfish can actively swim at counter-current in response to drift, the researchers report. They add that 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. It’s not yet clear exactly how the jellyfish figure out which way to go. The scientists say the animals might detect current across their body surface, or might 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 useful for predicting and avoiding troublesome jellyfish blooms, the researchers added. While jellyfish 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,” Hays said. “This will allow improved management of jellyfish blooms.”