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It might be a tiny sea snail, but that’s one hell of a shell


It might be a tiny sea snail, but that’s one hell of a shell

Periwinkles have a genetic trick that enables them to adapt remarkably quickly to their environment

Senior science reporter

’n Boer maak a plan.
But so does a periwinkle.
New research has shown that these remarkable little sea snails have developed a genetic “toolkit” kept in just three chromosomes to help them adapt to different environments.
Not just that, they have done this very quickly in evolutionary terms.
A group of researchers who went searching for the little creatures along the west coast of Sweden noticed that the way they were laid out on the shoreline was almost like a bar graph showing data in the real world.
Hailing from the University of Sheffield in the UK and the University of Gothenburg in Sweden, they investigated hundreds of rough periwinkles picked up along the same shoreline. Notes were taken on each periwinkle’s position on the shore, and the form of their shell.Their genomes were analysed and the results showed that when the crab was the biggest danger, the periwinkles had a thicker shell. But when the waves were the biggest danger, the snails had a wider opening to allow them to get an easier foothold on the rocks.
The results, published in Evolution Letters, showed the snails’ characteristics “changed significantly” at the point on the shore where the crabs disappear and the wave action gets stronger.
“Either side of the habitat transition, the snails look like different species,” said researcher Anja Westram. “Snails on the boulder shore have thicker shells, which are a better defence against crabs. The smaller, cliff shells have a wide opening, so the snail’s foot can attach more securely to rocks, to defend against waves. And across 10m to 20m of shore in between these areas, we found all kinds of intermediate forms.”
What is most unusual is that about 1,000 genes differ between the snails in the crabby area compared with the wavy area.
But, instead of being spread throughout the genome, most of them were “clustered in specific regions across just three chromosomes”.The researchers concluded that the chromosomes were holding together sets of genes to help the snails adapt to different environments.“This study gives us a fascinating insight into how animals and plants might cope when faced with contrasting environments,” says Professor Roger Butlin from the University of Sheffield.
“Rather than many genes having to respond separately to natural selection, this creates a ready-made ‘toolkit’ on these three chromosomes that has allowed the snail to adapt more rapidly.”
The team also worked out that these adaptations probably occurred within 5-6,000 generations, “a rapid change in evolutionary terms”.
The team is now looking at other shorelines around Europe to investigate how widely the same adaptive toolkit is used by the periwinkles.

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