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Lunar cycle triggers Hawaiian box jellyfish to spawn on Oʻahu shores

Lead author Angel Yanagihara with Hawaiian Box Jellyfish. (Photo credit: Keoki Stender)

A key number of hours of darkness during the lunar cycle triggers mature Hawaiian box jellyfish (Alatina alata) to swim to leeward shores on Oʻahu to spawn. That’s according to a published study comprising more than a decade of work by a cross-disciplinary team of University of Hawaiʻi at Mānoa researchers.

Led by Angel Yanagihara, associate research professor at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST) and the John A. Burns School of Medicine, UH Mānoa researchers have been carefully tracking local box jellyfish for more than 20 years. While the monthly shoreline aggregations are understood to occur like clockwork 8–10 days after each full moon, with jelly forecasts included on the local news, mysteries have remained: Why are they appearing at this particular part of the lunar cycle? Where do these box jellyfish come from and where are they found the rest of the lunar cycle? Why has this become a monthly problem in only the last 30 years?

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