| From: B.C. ® | 13/02/2001
8:21:49 |
| Subject: fishes and pressure | post id:
229233 |
| I have a question put to me at
work last night.I was'nt sure of the answer,so I will submit it here for
educated opinions.....at the depths of the oceans,the pressure is enough
to implode sub marines so how do the species of fish at that depth survive
such incredible pressure?Why are not these fishes squashed to
oblivion? | |
| From: Zardoz ® | 13/02/2001
8:43:49 |
| Subject: re: fishes and pressure | post id:
229237 |
| In the deep oceans, the pressure
of the water is immense! However, it's not necessarily the pressure that
causes problems for animals, but rather pressure differences. You may or
may not know that many fish have something called a swim bladder, which is
basically a bag of gas inside the fish. By inflating and deflating that
bag of gas, the fish are able to change their density (which allows them
to move up and down in the water. Now then, imagine if you were to take an inflated balloon and lower it into the ocean: the pressure of the water would squish the balloon down to nothing, right? The same thing would happen to a fish with a swim bladder- the difference in pressure between the gas bag and the water pushing in on the outside of the fish would squish it (if it were unlucky to go deep enough!) So, in order to avoid being squished like our balloon, deep sea fish DO NOT have a swim bladder, or any type of air cavity at all. NO air bag, no balloon effect, no squish. As well, deep sea fish also tend to have very gelatinous muscles, with a high water content, so that the pressure that is being exerted on them is exerted over their entire body. | |
| From: Dr Dirt | 13/02/2001
8:48:18 |
| Subject: re: fishes and pressure | post id:
229240 |
| OK but how do fish manage to
change depths rapidly without experiencing something similar to the
bends? | |
| From: Richard ® | 13/02/2001
8:51:51 |
| Subject: re: fishes and pressure | post id:
229242 |
| The bends is Nitrogen narcosis my
guess would be that as fish breath oxygen from the water they would have
0% or very low % of nitrogen. only my theory could be wrong though | |
| From: Zardoz ® | 13/02/2001
8:58:30 |
| Subject: re: fishes and pressure | post id:
229244 |
| Since 80% of the air we breathe
is nitrogen, our blood is full of dissolved nitrogen. The bends happens
when the pressure on a person is lowered quickly. Suddenly at lower
pressure, the blood can no longer hold all the nitrogen it's holding, so
some of the nitrogen comes out of the blood as little bubbles. These
bubbles can block the capillaries in the body and stop the flow of blood,
which is why the bends are so dangerous. When fish are underwater, they're not taking in any air, so they're not taking on extra nitrogen to fill up their blood beyond its surface-pressure capacity. They come up with the same amount of nitrogen they started with, which is no problem. That's why they don't get the bends. | |
| From: Martin Smith (Avatar) | 13/02/2001
9:04:42 |
| Subject: re: fishes and pressure | post id:
229246 |
What about sea mammals (whales etc). MS | |
| From: Zardoz ® | 13/02/2001
9:16:47 |
| Subject: re: fishes and pressure | post id:
229251 |
| People can free-dive (i.e. dive
without tanks) without worrying about getting the bends. Because when under water they are not getting any more nitrogen. The amount they went under with is the amount they have. Scuba divers take air tanks, and therefore more nitrogen into their system whilst under water and under water pressure. Whales take a big breath and under they go. No airtanks, no extra nitrogen whilst under water. No increase in nitrogen and no bends. | |
| From: Arno ® | 13/02/2001
9:24:49 |
| Subject: re: fishes and pressure | post id:
229257 |
| Zardoz, Does body surface area have anything to do with the amount of pressure? Arno | |
| From: mick ® | 13/02/2001
9:27:30 |
| Subject: re: fishes and pressure | post id:
229260 |
| fish can still suffer from water
pressure variation but these are fish "with" swim bladders caught from
reasonably deep water . if pulled to the surface quickly by a hook and line their swim bladders will expand and the fish comes to the surface easily. many fisherman carry a large needle or such to pierce the air bladder so that if they choose to release the fish it will not float on top of the water to be eaten by birds (apparently usually they survive ) | |
| From: DarrenK ® | 13/02/2001
16:04:50 |
| Subject: re: fishes and pressure | post id:
229649 |
| One extra thing about
whales: Apparently the deep divers actually have a jointed rib cage which collapses inwards as they dive, compressing their lungs and driving the gas into their blood stream. I guess they must allow the gas to bubble out into their lungs again on the way up. | |
| From: aquaman | 14/02/2001
1:21:05 |
| Subject: re: fishes and pressure | post id:
230181 |
| How about in the movies where
deep divers breath liquid saturated with oxygen. Apparently this could
allow diving to great depths by preventing the lung cavities from
collapsing. Is this bull? Are there other cavities in the
body? | |
| From: J.F. ® | 14/02/2001
22:51:50 |
| Subject: re: fishes and pressure | post id:
230904 |
| There are other cavities in the
body, that suffer "squeeze". OOTOMH, I can think of: the sinuses in our heads (ever had sinusitis?) The inner ear + associated tube to the oral cavity, (never dive with a cold) THe gut contains gas... | |
| From: mike | 14/02/2001
23:04:51 |
| Subject: re: fishes and pressure | post id:
230915 |
| i have a dive certificate and
when getting it i was told that the nitrogen was gained through the skin ,
the deaper, the more nitrogen the water will hold and it equalizers
through the skin, then it has to be exspelled though breathing on the way
up the submarine wouldnt impload if the air pressure inside was the same as out side but air would be used verry quickly | |
| From: Wags | 14/02/2001
23:11:26 |
| Subject: re: fishes and pressure | post id:
230924 |
| "deep divers breath liquid
saturated with oxygen" I have heard of this being done with rats in a lab but I am 100% sure it doesn't happen with divers. Serious deep divers use a TRI-MIX gas for the depths. Nitrogen concentration is reduced to reduce the effects of nitrogen narcosis which is reportedly like being on drugs. This effect isn't fully understood. Oxygen concentration is reduced to avoid oxygen toxicity. When the partial pressure of oxygen reaches approximately 1.6 (while diving on air roughly 80 metres) oxygen toxicity can cause convulsions that commence without warning. This is effected by duration as well as concentration. With reduced oxygen and nitrogen levels, helium is used to fill the void! | |
| From: Greg Mc ® | 14/02/2001
23:25:41 |
| Subject: re: fishes and pressure | post id:
230946 |
| Liquid breathing perfluorocarbons
has been trialed on human subjects and numerous other animal species. Some
US navy divers trialed liquid in both lungs but as far as we all could
determine, it has not been used operationally in the sea. It is however even used on premature babies. We had a few threads on this last year sometime with a zillion links included. I think the threads were simply called "Liquid Breathing". (Oh no, don't try the "aquatic ape threads"!) It is believed that the mucus of whales and dolphins has some nitrogen expelling properties that helps them deal with the small amount of excess nitrogen they pick up from their extreme diving habits. They also have some neat unique internal circulatory plumbing that heaps maintain the internally held male gonads at a lower temp than the rest of the body. | |
| From: pookie | 14/02/2001
23:49:04 |
| Subject: re: fishes and pressure | post id:
230980 |
| Liquid breathing in humans has so
far been unsuccessful as fluid in the lungs washes away the sefactant
which bonds the alveoli (like bunches of grapes where oxygen/carbon
dioxide transfer takes place) causing the alveoli to callapse, and
suffocating the person. sort of like a near
drowning. | |
| From: Greg Mc ® | 15/02/2001
0:10:55 |
| Subject: re: fishes and pressure | post id:
230999 |
| Ah, Pookie, in most of the papers
I have read, perflurocarbons can improve lung function and open up
collapsed alveoli in patients with lung distress. It acts as a surfactant itself. As an example ....... http://www.sybd.com/LV.html | |