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  • Writer's pictureSinead Mackintosh


Jellyfish come in all shapes, sizes, colours and although they may look relatively simple, they have a rather interesting life cycle. Jellyfish, coral and sea anemones are actually all distant cousins, and like its cousins the jellyfish starts its life anchored to the ocean floor.

So how do they go from stationary to floating across the ocean? Well in 2019 researchers discovered the genes that help them do just that. In the beginning of the jellyfish lifecycle, they transform from larvae into polyps. Polyps look like stalks and are stuck in sediment, and this is the stage that coral and sea anemones stay at. Jellyfish, however, overcome the polyp stage and move into the medusa stage and become the free-floating jellyfish that we are familiar with.

Researchers compared the genes of the moon jellyfish (aka “water jellyfish” or “Aurelia aurita”) and the giant box jellyfish (aka “fire jellyfish” or “Morbakka virulenta”). They found that when the jellyfish finish the polyp stage, certain genes are switched on to allow it to develop into their characteristic form. These genes separate the jellyfish from their sedentary cousins and allow the jellyfish to develop certain organs and specialised swimming muscles.

Beyond their shape-shifting abilities, some species of jellyfish like the box jellyfish are some of the most venomous animals in the world. Researchers also identified a gene called “CqTx” which makes a toxin that makes holes in cell membranes causing red blood cells to die. The toxin is so powerful that it can stop a human’s heart in 5 minutes. The hope is to use these genes to help make antivenoms and investigate therapeutic uses as potential drugs.

Jellyfish lead a more complicated life than most people realise. And who knows, maybe one day, we can be taking medication based on jellyfish venom.

By Alexander Vasenin - Own work, CC BY-SA 3.0,

By © Hans Hillewaert, CC BY-SA 4.0,

By Ernst Haeckel - Kunstformen der Natur (1904), plate 78: Cubomedusae (see here, here and here), Public Domain,

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