Re: Do all worms sleep?

Dear Alissa,
Let me ask you a question. How can you tell if a worm is sleeping? You 
can't tell by their eyes, because many worms don't have eyes and the ones 
that have eyes can't close them like humans and some other animals 
(for example, cats, dogs or birds) do when they are sleeping. Being 
motionless is not a good indication for being asleep, because a worm that 
appears to be motionless to us could be doing something else that we can't 
detect. Neither does being unresponsive to mild stimuli mean that a worm 
is sleeping. Some worms and other invertebrates, for example land snails, 
can become dormant for long periods, sometimes for several months, when 
their environment is too cold, or too hot or too dry. When they are 
dormant, they stop moving and their metabolism slows down. One may 
consider that they are sleeping. But I don't think dormany is 
physiologically the same phenomenon as sleep in other animals. So, the 
point is, sleep is not a concept that we can use to discuss the behavior 
of worms and other invertebrates.

Aydin Örstan