How can you tell if a worm is stressed ?

Question: How can you tell if a worm is stressed ?
- Keywords:
  stress,
  worm
Asked by 237rhed39 to Rachel on 8 Nov 2015.
- Rachel McMullan answered on 8 Nov 2015:
  
  Hi,
  I get asked this question quite a bit, the short answer is that you can’t!
  But we can still use them to study what happens in your body when you’re stressed.
  When you’re stressed there are lots of changes in the chemicals in your brain. Worms have some of these chemicals too, (we call them neurotransmitters) and they control how worms moves. Some of them make the worms slow down and some make them speed up, or move differently. By looking at how worms move we’ve learnt a lot about how these chemicals work.

Question: How can you tell if a worm is stressed ?