So how do they? I saw some documentary on marine mammals awhile back and even they didn’t really explain it. They talked about human divers having to worry about the bends because we breathe compressed air and whales hold their breathes (and I heard the same explanation for deep sea sport divers), but HOW does that prevent the bends?? Doesn’t the air compress inside the whale anyways when it dives down?? So far I can think of these things off the top of my head that should be killing whales and dolphins left and right:
The bends
Nitrogen narcosis
Just plain crushing from the pressure (I know lots of animals live at the bottom of the ocean, but don’t they always stay there? How does the whale’s body survive both at the top and bottom?)
Air embolism
Some wiki articles I’ve clicked on (which is how I stumbled on this topic to begin with) seem to say sperm whales have the ability to go ahead and just let their lungs collapse and store the air molecules directly in the muscles. I guess that could kind of explain the atmospheric crushing, but I don’t totally buy it. So…what makes whales so special?
Weird, that link doesn’t fully load for me. It shows the title, then it says it fully loaded and there’s nothing on my browser. Thanx for trying, though =)
That’s odd, still works for me. I’ll summarize though: Whales may not be immune to the bends - a couple of scientists have discovered pits and gaps in whale bones that are indicative of decompression sickness.
I don’t know much about the physiological adaptations that allow whales to handle immense pressures, but the reason they don’t get the bends is that the bends are caused by breathing compressed air. The pressure of compressed air is required to allow the lungs to inflate despite pressure from the water. Because it is compressed, it contains higher amounts of air’s components, the most abundant of which is nitrogen. This additional nitrogen goes into solution in body fluids when a diver spends time below 33 feet, and it comes out of solution on the way back up. If the diver comes up gradually, this is no problem, but a quick ascent can causes the bends as the nitrogen bbubles like carbonated water. Whales breathe in air at normal pressure, so there’s no extra nitrogen to go into solution.
No, it is just under pressure. It doesn’t contain “higher amounts” of air’s components, it just has the same amounts at higher pressure, which forces nitrogen into solution when it would not be at lower pressure.
I doubt this. At great depth, unless they have lungs that are built like a bathyscape (ie to withstand incredible external pressure without compressing the content) any air in their lungs will be compressed to the depth they are at. Exactly like a diver.
Actually, Maastricht’s link suggests my last post is only partially correct. Apparently, below about 330 feet the whale’s lungs collapse under pressure altogether, so there is no air left in the lungs to be compressed. However, my answer seems to be right down to that depth.
Though I can’t seem to find a useful link just now, I’ve always understood that, as Crotalus suggests, whales’ primary oxgen supply for deep dives is what they’ve put into their blood while breathing on the surface - what’s in the lungs is minor. There is limited transport of compressed gas into the blood, and thus little opportunity for bends or nitrogen narcosis.
Embolism can’t really be a problem when breathing air at the surface. What expands as you rise can only be what has compressed as you descend.
But doesn’t the air compress as you decend and so you end up with the same problem? If it’s fast like the sport divers who hang onto weights and drop themselves a couple of hundred feet, then I can believe it. But if a whale slowly descends for over an hour, isn’t the water pressure going to compress the whale and its air contents and give you the same problem? The key might be here. My intuition would say that air that hasn’t been compressed outside the body won’t compress inside the body without the body itself first compressing significantly (read, fatally), but for some reason I think we covered this topic in physics and it turns out that yes, it does compress. Anyone to correct me on this?
WonJohnSoup, the whale is going to absorb oxygen (not air) into its bloodstream at the surface. So as the water pressure comes onto the whale, there is not going to be air (and in particular gaseous nitrogen) available to be forced into the blood.
There’s no compelling reason for whales to descend slowly - they’re generally headed down for food, and they’d like to get there rather promptly to give themselves time to catch it.
But fast or slow, they’d certainly have a problem if they contained significant amounts of air or any gas in gaseous form. They don’t - the gases they contain (plenty of oxygen to start, a lot more CO[sub]2[/sub] as they return to the surface) are dissolved, and thus whales don’t get compressed like a balloon would.