Golden jellyfish

How it lives

Golden jellyfish live in marine lakes, bodies of seawater surrounded by land. The golden jelly of Jellyfish Lake (Ongeim'l Tketau) in Palau, Mastigias papua etpisoni, is found only in that one lake, and algae in its tissue make food from sunlight, so the jellies swim toward the sun. They still have stinging cells; the sting is often too mild to feel, but it can tingle on sensitive skin. Golden jellies in Indonesian marine lakes, such as Kakaban Lake and lakes in Raja Ampat, belong to different lineages, and scientists are still working out how many species there are.

Where it goes

Not a migrant, but a daily traveller. On sunny mornings the jellies in Jellyfish Lake swim east toward the sun and stop at the shadow line of the trees, then turn west after midday. On cloudy days they spread out through the lake. Their route shifts toward the south edge from October to March and toward the north edge from May to August.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

Jellyfish Lake usually holds millions of golden jellies, often about 5 million. When the lake gets too warm they stop reproducing, and after strong El Niño droughts they almost vanished in 1998 to 1999 and again in 2016, when the last one was seen in May 2016. Tiny polyps survived, and numbers came back to millions by 2019. In 2022 warm water brought them down to about 34,000, so numbers and lake access change from year to year.