Race to identify mystery box jellyfish after painful stings at Sydney beach

Swimmers in Sydney believe they could have been stung by the creature.

Swimmers have been reporting painful stings around a Sydney surf beach, raising concerns they could be from a mysterious box jellyfish first spotted in 2022.

Marine scientist Sarah-Jo Lobwein is part of a dedicated team that’s working to understand more about the creature and whether it's dangerous to humans.

She’s been collecting images of both the jellyfish and the red welts they may have caused to beachgoers around Cronulla. “You can see the lines from the stinger cells, the welts on the skin,” she said. “Different jellyfish can make you feel different, you feel like you’re on fire, it’s very different to a bluebottle sting.”

Left - one of the mystery box jellyfish in the water at Cronulla. Right - a sample in caught and taken to the museum.
A mystery box jellyfish has been collected from waters in Cronulla and is now being analysed by scientists. Source: Jason Gilmore/Brett Lobwein

What are the symptoms of suspected jellyfish stings?

Because everyone reacts differently to stings it’s unclear whether they’re being caused by the common jimble jellyfish frequently seen in the area, or a separate unidentified species believed to be a box jellyfish.

“I’ve have been contacted by at least two people who think they've been stung, but they could have been stung by other species,” Ms Lobwein said. “If people think they have been stung we really need a photo.”

Encounters with the mystery jellyfish were captured for the first time on video by ocean swimmers in May last year. Then they apparently disappeared over summer.

New sightings were once again reported in April, 2023 and for the first time a live animal was collected on Anzac Day, then another three days later. They were shipped to the Australian Museum where its marine experts are trying to determine if it is a new species.

Video shows the mystery box jellyfish up close

Are box jellyfish a problem in Sydney?

Australian box jellyfish prefer warm tropical waters and are found along Australia’s northern coastline, from Western Australia to the Northern Territory and Queensland. It is considered by US authorities to be the world's most venomous marine creature.

While there have been sightings of jellyfish associated with the tropics in southern waters, in previous years they have quickly died out. Researchers suspect they’ve travelled in the ballast of ships.

Surf lifesavers and other beachgoers at Cronulla.
Swimmers reported seeing mystery box jellyfish in 2022. Then they disappeared. Source: Getty (File)

Because of climate change and changes in currents from La Nina, in recent years there have been changes to the ocean landscape. This has included thousands of strange-looking blue-coloured sea creatures washing up on Sydney’s beaches in what’s known as a “blue fleet”.

However, Ms Lobwein said it’s possible that it has existed in Sydney’s waters but was never noticed. “We’re in an era of GoPro now, everybody has a camera in the water” she said.

What should I do if a friend is stung by a box jellyfish?

The Australian Museum recommends the following steps to treat box jellyfish stings:

  • Call emergency services on Triple 0 or 112.

  • Be prepared to give CPR.

  • Keep the patient calm.

  • Don't rub the area.

  • For at least 30 seconds flood the affected area with vinegar.

  • Apply a pressure-immobilisation bandage.

Differences between jimbles and the new jellyfish

Jimbles have just four tentacles and have painful, but not usually life-threatening stings.

The body of the mystery creature resembles that of other box jellyfish. It has multiple tentacles and features of both lethal and non-lethal species. A new species of box jellyfish was discovered in China this year.

Stinger suits are commonly worn in Australia’s tropics during the summer months as they reduce the risk of being stung. Anyone who sees a box jellyfish in Sydney is urged to avoid contact with it. Images taken from a safe distance can be sent to Ms Lobwein at info@soshire.org.

“We've still got so much to discover, so there's so much out there in the ocean that we don't know about,” she said.

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