How do earthworms move?

04 December 2018

Question

How do earthworms move? Surely they are not strong enough to push dirt / soil out of their way, so how do they move around in compacted soil?

Answer

Chris Smith put Paul's earthy question to animal behaviourist Eleanor Drinkwater...

Eleanor -  Well this is a brilliant question and if you think about it, like you know, how does this little blob of pink kind of manage to wiggle its way through such hard earth. And the answer is: it's all about fluids. So if you've ever had a water balloon and you grab one end the other end kind of shoots out, and that's kind of what's going on in worms. So if you look really carefully you'll see that they're segmented all the way down their bodies. It has two sets of muscles, one that'll make the segment kind of long and then and the other one will make it short and fat. And so it's a kind of combination of these muscles working interchangeably, changing the shape of the segment without changing the volume of the segment.

Chris -  So you've got a muscle that goes, or muscles, that go along the length of the worm and when they contract them make it short and fat vs. muscles that are in rings around the world making it get thinner and longer when they squirt or squeeze.

Eleanor - In principle, yes.

Chris - And it's using the antagonistic effects of those two to change its shape. How does that push a tiny worm through soil?

Eleanor - So it's a bit like an accordion, the way that they all kind of contract together and space out, and it's just incredible to think about the fact that each segment in this worm can move and contract independently. I just think it's mind blowing personally, it's amazing.

Chris - Don’t they eat their way through the soil as well? Because you know when I lived in Sydney these people introduced me to their wormery and said we put all our household rubbish on this and they turn out worm juice and this is plant magic, it's like gold dust for plants it makes everything grow.

Eleanor - Yeah they do eat vegetation in the soil but they can also whittle through it as well.

 

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