[neilep (OP)]

Dearest All,

Happy Blimmin Monday !!...grrrrrrrrrr !!


This is me in my aquarium with my pet Shark Sandra,

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We're an item !!...she goes all floppy when I hold her !!... []

why !!?...why do sharks almost go like into a trance when you handle them....I think especially when you hold their snout !!

[Karen W.]

I just heard that and thought it only worked with alligators, stroking the back of their head or something they fall asleep!

Thats pretty cool but I do not know why!

[Alandriel]

Hmmmmmm good one! []

Never had that with any of my sharks LOL - so it must be you!

I've heard of this before however, now that you bring it up a memory stirs. Though I've closely observed many sharks (many species), I've not handled that many. I can tell you that white tips, black tips and nurse sharks do not oblige like this and I certainly would never try this with a tiger. Perhaps it's species dependent or even influenced by the environment.
Would be interesting to find an answer - I'll go digging a bit.

What type of shark is this and where?

and ps: next time you do this DO wear gloves! []

[Carol-A]

I may be wrong, but I thought sharks had to keep swimming to breath.... so perhaps stopping them makes them a bit short of breath...

[Alandriel]

That's probably quite true for many sharks, Carol.

However, some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest; hence you have the phenomena of 'sleeping' sharks.

[neilep (OP)]

CHECK THIS OUT

THANK YOU ALL FOR YOUR COMMENTS SO FAR

[JimBob]

But no-one has answered the question why?

I know when someone rubs my stomach things happen but then again, I am not a shark. Well, most of the time, that is.

[neilep (OP)]

But no-one has answered the question why?

I know when someone rubs my stomach things happen but then again, I am not a shark. Well, most of the time, that is.

....and it looks like no one is going to answer it too !!

 [] []

[Alandriel]

There is a lot more we DON'T know about sharks than we do know ....

and that goes not only for sharks but for many other marine species. Comes with the territory I guess

unless, we grow gills or find a better way to deal with dive table limitations []

[neilep (OP)]

*le sigh*....I'll email the Man From Atlantis  http://en.wikipedia.org/wiki/The_man_from_atlantis


Perhaps I can speculate !!.....I wonder if this kind of close interaction, specifically around the snout, interferes with the Sharks sonar capabilities somehow !!...and the result being a type of ' close down '

[Karen W.]

It looks like just being upside down might induce the sleep or like a loss of consciousness... I don't know!

[Andrew K Fletcher]

The nervous system requires the constant pull of gravity in the correct direction through the shark’s body! Turing the shark, eel, crock, gator upside down sends the tiny pulses of salts that drive the spinal fluid in the wrong direction slowing and even shutting down the nervous system by compromising the circulation. Easily verifiable in a laboratory using barium or some other active substance to monitor circulation changes, but I guess its easier to carry on believing that gravity does nothing in the nervous system. Multiple Sclerosis has been shown to relate to high humidity in river valley areas and low laying coastal areas!

Catatonic state from reduced motor activity in humans and animals is not uncommon. Indeed sleep is a mild form of it, and sleep paralysis can be induced when the body position or posture of a person is incorrectly aligned with gravity. Placing a person who is catatonic in a compromising posture can cause that person to remain in the same position for very long periods. Oliver Sachs who the film Awakenings  represented was faced with an unusually large number of people subject to catatonic state. This was believed to be caused by a form of encephalitis which causes inflammation of the brain. Yet as Sachs showed, the use of levodopamine (Ldopa) revived the patients temporarily before the onset of overdose caused severe malfunction in the nervous-system that was considered to be worse and more dangerous than the catatonic state.

I have written to Sachs on numerous occasions but I guess he is a very busy man, too busy to listen to someone who might just have found the common denominator in the sleepers who are in catatonic state. I believe that an increase in humidity can initiate the slowing down of the nervous system and suspect that high humidity was the cause of the encephalitis that led to the catatonic state, and indeed have related this to how dolphins and whales have to migrate in order to escape from very high humidity which significantly reduces their ability to outrun the trawlers nets and reduces their ability to stay under water and hunt for food. I also believe this is why pilot whales beach themselves and die while trying to avoid drowning. The humid air according to my own research would compromise the oxygenation capacity of the lungs and alter the flow of the cerebrospinal fluids by reducing the density changes caused by gas exchange from the respiratory tract.   

Andrew K Fletcher

[BenV]

All well and good Andrew, but in the video the shark is put into a 'trance' before it's alignment is changed, we can assume the same applies before the picture and so in this situation the effect of gravity is irrelevant.

Sharks have cells that are extremely sensitive to electric fields, usually concentrated along the snout.  This is why hammerheads have hammer-heads - to extend the area available for the electro-sensitive cells.

The diver in the video has chain mail gloves on, which are likely to effect electric currents, so I'm assuming that the contact is affecting these cells, as Neil suggested, and so altering the shark's behaviour.

[Andrew K Fletcher]

This video is not relating to the deep catatonic state induced by laying the shark on it’s back. But relates more to an enjoyable sensation that stupefies the recipient, in the sharks case the sensation is from gently stimulating the front of it’s mouth. In a bull terrier the same state can be induced by drawing a figure 8 continuously on the tummy. We use this method when showing dogs as it relaxes the dog and avoids any nervous reaction towards the judge or other exhibiters.

The bull terrier also massages it’s own head under a tree, usually the Christmas tree or a large house plant. They go into ultra slow motion mode, it has us rolling the floor with laughter when they do this.

But again not the same reaction as turning a shark or gator on their back.

this video is interesting. It shows a shark upside down reacting as a magnet is drawn near to its head, even when behind a plastic barrier.