What is the advantage for an invertibrate to not have a spine?

Question: What is the advantage for an invertibrate to not have a spine?
- Keywords:
  advantage,
  invertebrate
Asked by michelletherezien to Charlotte, Jo, Kevin, Louise, Valeria on 19 Jun 2012.
- Joanna Cruden answered on 19 Jun 2012:
  
  This is such a good question, I think that without a spine they can squeeze into tiny gaps, to hide from predetors or attack passing prey, that having a pesky spiine prevents them from doing!
- Kevin Mahon answered on 19 Jun 2012:
  
  Also not having a spine is what allows them to develop their exo-skeletons; which are much more protective than just skin, which is clearly a useful defensive tool in the wild !

Question: What is the advantage for an invertibrate to not have a spine?