Sea anemones grow new arms as they develop
The number of tentacles that sea anemones grow isn’t set genetically. Instead it depends on how much they have to eat.
If the same were true for people, it would mean that the more we ate, the more arms and legs we would grow, says Aissam Ikmi at the European Molecular Biology Laboratory in Heidelberg, Germany.
In animals, both body shape and size are usually genetically determined. There are only a few known exceptions, such as Galapagos marine iguanas, which shrink by as much as 20 per cent during bad years. The iguanas don’t just lose fat, they reabsorb bone tissue.
Now Ikmi’s team has studied 1000 polyps of the sea anemone Nematostella vectensis. The researchers found that the number of tentacles they have is determined by the amount the anemones eat. The growth of new tentacles can continue throughout adulthood if enough food is available.
It isn’t just a matter of size, says Ikmi. The emergence of new tentacles is related to the relative change in an individual’s growth, rather than their absolute size.
“You can find smaller anemones in a culture dish that have more tentacles than larger polyps.”
Journal reference: Nature Communications, DOI: 10.1038/s41467-020-18133-0
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