An unusually huge toxic jellyfish has been found off the north-west coast of Western Australia.
The Keesingia gigas is one of two new species of Irukandji jellyfish recently discovered by scientist and Marine Stinger Advisory Services director Dr Lisa-Ann Gershwin.
Dr Gershwin says this jellyfish is of particular interest because it is so much larger than usual jellyfish causing Irukandji syndrome, resulting in pain, nausea, vomiting and in extreme cases, stroke and heart failure.
"It's just a whopping huge animal. We normally measure Irukandji in terms of size of your pinky or thumb nail—this one is more the size of an arm," Dr Gershwin says.
Dr Gershwin says the Keesingia gigas was first photographed in the 1980s but a specimen was only captured in 2013 near Shark Bay by marine scientist and Dr Gershwin's previous supervisor John Keesing, after whom the jellyfish is named.
"I had been looking for a specimen for more than a decade and John had been out doing a research project and saw the jellyfish swim by the boat and managed to catch it," Dr Gershwin says.
At the time, it was misidentified but after studying the specimen's DNA Dr Gershwin found it to be completely unique.
"From a scientific, evolutionary point of view, it has some diagnostic features of two quite distant families," Dr Gershwin says.
"My guess is it's a matter of convergent evolution where, because of similar functions in the ecosystem, there are very different organisms that have similar appearance and structure features."
Dr Gershwin says the jellyfish did not appear to have tentacles both in the specimen and all of the photos.
"I am intrigued by the lack of tentacles. On the one hand, we have such few samples that maybe we just haven't got a sample yet," she says.
"I don't see how they would be able to catch food or defend themselves without tentacles. So maybe it's a little bit more complicated and it does stuff in a way we just don't know yet."
Another smaller Irukandji from Exmouth, Malo bella, has also been described.
The two new species bring the total number of Irukandji jellyfish worldwide to 16 and the total from WA to four.
Dr Gershwin says she finds WA fascinating because there is so much still to discover.
"Literally every time I dip the net in the sea, I find a new species. It's like Disneyland for marine biologists."
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