Meet Keesingia gigas, one of a pair of new species of Irukandji jellyfish recently discovered off the coast of Western Australia. It's confusing researchers because it appears not to have any tentacles.
Actually, Kessingia gigas isn't actually new. It was first photographed in the 1980s, but it wasn't until last year that a live specimen was captured. New or not, this is one weird Cnidarian.
Most jellyfish keep their stingers in their tentacles, it's how they capture their prey or avoid becoming somebody else's prey. And while it's been known for some time that jellyfish in the Irukandji group - it's not a taxonomic designation, but an informal one describing the now 16 species that can cause Irukandji syndrome - also have stingers in their bells, this is the first that appears not to have tentacles at all.
Irukandji syndrome is pretty nasty. It involves severe headache, backache, muscle pains, chest pains, abdominal pain, nausea, vomiting, sweating, anxiety, hypertension, tachycardia, and pulmonary edema. One of the weirder aspects is that those who have been stung almost universally report a "feeling of impending doom." Scary stuff.
But what's with the no tentacles thing? The Guardian explains:
Gershwin said the species could shed its tentacles as a means of defence, like some bioluminescent jellyfish that drop their glowing tentacles in order to distract predators, but there was no evidence that any Irukandji had that capability.
"I think more probably it does have tentacles but by random chance the specimens that we photographed and obtained don't have them any more," she said.
"I think it's probably a fairly tame explanation – I just don't know what it is."
In the meantime, if you're diving off of Western Australia and you see something that looks like a plastic shopping bag floating around, you might think twice before trying to grab it. Irukandji syndrome sounds completely awful.
Read the whole paper describing Keesingia gigas, courtesy of the Western Australia Museum.