[neilep (OP)]

I've just seen a prog where tourists pay to go and have enounters with sharks, nothing strange there, there's a few people I know who I would gladly throw to sharks for free [] but what is fascinating is the way how easily the sharks seem to be put into a trance by rubbing their noses and turning them upside down, to the point that when they're in 'happy hypnotise land' you could almost do whatever you like with them !!! play golf, tell jokes etc []... but seriously what is happening here  do you think ?...what process is happenning in happy sharks brain to turn them into delinquent docile big fat fish ?


fin


'Men are the same as women...just inside out !'

[roberth]

They might call them hypnotised, but they are really in a type of  coma. Sharks, unlike most aquatic animals, need to keep moving to continue the oxygen flow through their gills. They even continue to move while asleep! When they stop (they rub their nose to stop them), their brain goes into shutdown mode and supplies oxygen to only life supporting organs, so while they appear like docile big fat fish, they are just half dead. I think they turn them over to disorient them. When they wake up, they are really p!ssed off and want to eat something, so a little disorientation helps the people playing with them to escape.

[tweener]

Sounds like a good theory to me.  But I've heard that some types of sharks (Nurse?) have been found being very still for several hours at a time.  

I believe that turning over an alligator also renders it pretty much inert.  This happens because their brain (about the size of a pea) is suspended in fluid.  When they get turned upside down, it puts pressure in the wrong place and they pass out.  Maybe the same thing is happening in the sharks (about the same size brain).  Maybe when they wake up they are so pissed because they have a headache.

----
John - The Eternal Pessimist.

[neilep (OP)]

I've just turned myself upside down and I feel fi.............................................!!

But thanks for your answers Roberth and John, fascinating stuff...I don't suppose there is a definitve answer but the plausibility of yours Roberth sounds convincing, and the next time a pissed off alligator  approaches me in the local swimming pool Roberth, I'll trick it into a 'backstroke' race....I'm bound to win !!!

'Men are the same as women...just inside out !'