What jellyfish can show us about complex evolution through simple genomes

1-14-2019 jelly cc
A Pacific sea nettle (Chrysaora fuscescens) at the Monterey Bay Aquarium in California, USA. Image credit: Dan90266/Flickr

You might expect that as bodies became more complex, genomes did as well.

But a recent study appearing in Nature Ecology & Evolution shows that not to be the case — at least for jellyfish, humble organisms that evolved at a crucial juncture in animal history. They did not need more genes — or even notably different ones — to power their giant leap in complexity.

Medusas actively hunt plankton and navigate the water column with neural sensory structures that detect light and orientation. To go from being a stationary polyp to a floating medusa is almost akin to humans evolving the ability to swim through the air and capture birds with springy, netlike appendages.

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If a radical shift in life history requires a big boost in gene content, the Aurelia genome should be riddled with novel genes unique to jellyfish. Instead, Gold found that, broadly speaking, “there really isn’t a whole lot of difference between Aurelia and their relatives with simpler lifestyles.”

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In any case, for now, the genetic changes that orchestrate this metamorphosis in jellyfish remain unknown. The transformation may depend on regions of the genome that don’t encode proteins, but instead regulate when genes are turned on and off. Perhaps it’s easier for life to innovate by rearranging its existing gene networks instead of evolving scores of new genes.

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Read full, original post: Jellyfish Genome Hints That Complexity Isn’t Genetically Complex

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