Giant, deadly jellyfish baffles scientists

Researchers caught a new species of jellyfish off Australia's northwest coast in 2013 — and they still can't explain it.

The Keesingia gigas is a recently discovered type of Irukandji jellyfish — but unlike its fingernail-sized cousins, Keesingia gigas is about the length of a human arm. Like all Irukandji jellyfish, it carries a potentially fatal venom that can cause pain, nausea, even stroke or heart failure. That's scary, but explainable. What's head scratching is that no specimen of Keesingia gigas has ever been photographed or collected with tentacles.

The discoverer of the species and director of Australia's Marine Stinger Advisory Services Lisa-ann Gershwin spoke to The Guardian about why this is so baffling:

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Gershwin later hypothesized that perhaps just the specimens they've seen don't have tentacles, before adding "I just don't know what it is."