The Terrifying Truth About Jellyfish

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Image: Alexandra Roberts

Box jellyfish

Like a creative flourish from God’s paintbrush, they are a dash of colour on the high seas, bringing both beauty and death wherever they go. Largely ignored by science for decades – outside of the Far East they’re not commonly eaten, and so of little commercial interest – these poorly-understood creatures have recently been in the news for all the wrong reasons. Unexplained swarms of these enigmatic invertebrates have been causing trouble in Hawaii, Spain and Northern Ireland. Scientists have begun asking questions about jellyfish, and the answers may just undermine what we think we know about the origins of diversity on earth…


Image: Matteo Tarenghi

Jellyfish trio

Jellies and comb jellies have recently reminded us that almost anything we think we know about evolution is apt to be overturned at a moments’ notice. Creation ‘scientists’ must be rejoicing. Comb-jellies (like the one below) are not true jellyfish, as they lack stinging cells. They’re members of the group ctenophora. But even true jellyfish continue to muddy our simple, logical ideas about evolutionary succession.

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Image: National Science Foundation

Comb jellyfish

See, according to their morphology, jellyfish are simple animals. They’ve no ‘front’ end, so they function perfectly well from any angle. They lack the central layer of embryonic tissue found in higher animals that develops into muscles, but they do have rudimentary eyes and nervous systems. In the traditional evolutionary tree, these features place them neatly between sponges and bilaterans (creatures with a front and back, like us). Later, when animals became bilateral, they were able to develop specific organs for different parts of the body, and this gave rise to the incredible increase in diversity known as the ‘Cambrian explosion’. But when things fit together that neatly, you know it’s too good to be true.

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