Name an animal, other than humans, which farms its own food. Perhaps another primate? No. Some little-known marsupial that has been farming for millennia, undisturbed by man? Nope. What about a worm? Yes! Now an ordinary worm has been observed planting seeds, waiting for them to grow, and then eating the sprouts.
The worm is the marine ragworm, and the seed is that of cordgrass, which the worms have previously been seen to carry back to their burrows, presumably to eat. But the cordgrass seed's husk is too tough for a hands-free, tool-free worm to break open so, says New Scientist, and it was a mystery how they managed to eat it.
Now, thanks to a team at the Royal Netherlands Institute for Sea Research, we know that the worms are farming these seeds. They take them home, tuck them up in their burrows, and wait for the seeds to germinate. When the seed sprouts, the worm has a delicious dinner that it has grown itself. Further, these seed sprouts are a kind of superfood for worms, so nutritious that the worms grow faster from eating the sprouts than they would if they could somehow choke down the husk-covered seed.
"The process of sprouting improves the digestibility and quality of the food," lead researcher Zhenchang Zhu told New Scientist.
This gardening behavior may have arisen spontaneously. The worms' seed-gathering behavior was previously thought to be simply a way to store and protect the seeds from being washed away by the sea. But the key here is that the worms wait for the seeds to germinate instead of eating them immediately.
Zhu and his team thinks that the industrious ragworm might be growing other food in its burrows, too. Specifically, he thinks that they are cultivating bacteria to eat. Zhu also speculates that other animals might also cache seeds and allow them to sprout.
"Our findings suggest that sprouting may be a common strategy used by seed-collecting animals to exploit nutrients from well-protected seeds," says the report. "Possible candidates are rodents that cache nuts and seeds with hard shells."
Human agriculture likely started off in a similarly simple way, which means that, once we have made ourselves extinct with climate change, the worms will probably hop (or slither) into our combine harvesters, and rule the Earth.