like your thoughts on these questions

[Graeme]

There are still some adaptations required to deal with high pressure, since it tends to reduce the fluidity of cell membranes and interfere with protein function. I'm sure there are also lots of other physiological consequences.

Yeah, that's right! Also, calcium is soluble at that pressure, which is why a lot of invertebrate critters down there have silica exoskeletons, instead of calcareous ones... if I remember correctly.

What do they do with the carbon dioxide, and how do they deal with decompression on their way back up?

Erm... I think it's got something to do with them having a more efficient breathing mechanism than us. I can't remember exactly, but they've got a greater tidal volume when breathing (I mean relative to a human's- size for size), use of Myohaemoblobin, which I can't remember, but I think it might bind with CO2 as Haemoglobin binds with O2 (or maybe Myohaemoglobin just binds with more O2 than Haemoglobin, I really can't recall). They also have a reduced reaction to CO2 anyway, but I'm not sure how. Plus they take deeper and less frequent breaths than other mammals, to begin with. A Diving reflex. They also have a greater blood volume, being around 10-15%, compared to us, which is about 7%. This means way more storage of oxygen. I'm not sure about the Bends though, which is brought about when the Nitrogen part of air, that's in your blood, dissolves at pressure, and then reforms as a gas again when the pressure lessens, causing bubbles in you bloodstream. I'm guessing that they may suffer from it.

Graeme

 

[OB]

Cetaceans use their muscle tissue for oxygen storage, by means of the aforementioned myoglobin.

Their lungs are free to collapse under pressure, as their saturating breathing prior to a prologed feeding dive (up to an hour or so in sperm whales...) allows them to draw oxygen from internal storage, rather than from the relatively small volume of air inhaled at the last breath at the surface...

 

[Nik]

My if i may? The last breath sperm whales take is thought to be for vocalisation/biosonar so is maintained in the nasal passages and airways, not the lungs, although since they're not breathing at depth there's little possibility of rupturing lung tissue on surfacing.

There are indications of decompression damage in sperm whale bones, mostly in older animals. See: http://www.sciencedaily.com/releases/2005/01/050111173124.htm Quite how they manage the effects of decompression under normal circumstances is not certain, however, rapid surfacing caused by a whale being disturbed during a dive (possibly by some sources of loud underwater noise) are thought to be responsible for decompression sickness possibly leading to stranding. At least, that's what i hear.

Cheers
Nik

 

[OB]

Good call on the reserve air! Sperm whales need it for both detection as well as stunning their prey. The latter is still a bit of conjecture, but given the absolutely huge accoustic lense they have in that forehead of theirs...

On decompression: air goes in at 1 bar and gets pressurized by the surrounding waterpressure acting on the whale's body as the animal dives, but as a consequence the volume goes down, so: there should really be no decompression related overfilling (causing rupture) or caisson type bubble formation in the animal as it surfaces. You can't have oversaturation if no hyperbaric air entered the lungs to equalize the pressure at depth.

The strandings hypothesis based on (underwater) testing of new types of extremely loud sonar, is more likely related to internal damage and haemorraghing of the ears, mainly, not decompression. This type of damage was seen in strandings just following sonar testing, nobody seems to think that's a coincidence.

I know that there are reports on stranded beaked whales, showing signs of the bends following sonar excercises. How to explain that from a physicist's point of view, I wonder.... Partial gas pressure increases, forcing excess nitrogen into the bloodstream?

I also wonder whether the "recent" Spanish strandings of five Architeuthis in one week were likewise correlated to testing at all, hmmmm. Could just have been mating season, of course...

 

[um...]

Regarding decompression: I would expect that the increased pressure would lead to greater solubility of nitrogen in the blood, which could still present problems in a too-rapid ascent. I appreciate that the relative volume of dissolved gas is lower when supplied from a single lungful taken at 1 bar than from a continuous high-pressure stream (as used in SCUBA dives), since there's simply less gas available in the former situation. According to these guys, (possible) osteonecrosis has been observed in whale skeletons that predate sonar by many decades. Still, I suppose that decompression may not be much of an issue in the normal life of a whale (or any other deep-diving animal).

 

[OB]

Looks plausible to me. I wonder what would happen if I forcefed a spermwhale with corn, send it down to, say one and a half kilometers below, and then dangle some nice fresh squid near the surface....

 

[main_board]

I find it interesting that the whales are still affected by the bends. They clearly have evolved adaptations to deal as best they can with such circumstances, but you'd think after so many years of this kind of behaviour that they'd get to a point where it no longer affected them. Hmmm! Very interesting, none-the-less.

Cheers!

 

[Snafflehound]

It's hard for evolution to overcome the laws of physics, more's the pity. But some of the solutions it does come up with are quite interesting. I mean, the shark, the icthyosaur and the dolphin all more or less have the same outer shape, but the shark doesn't have sonar and neither the dolphin or the shark have those huge ictyhosaur eyes.

It makes one wonder about the evolutionary path followed by the sperm whale. Which came first, eating squid or diving deep? It seems to me that the ancestor of the sperm whale may have eaten smaller squid at the surface; evolving to be able to dive deeper, brought it to a range where it could begin to predate giant squid.

 

[bigGdelta]

From what I understand pressure does funny things to enzymes like changing the shape of the molecules so they are no longer as efficient. So deep living organisms have evolved different enzymes than their shallow water cousins. i wonder if sperm whales take advantage of the chemical changes caused by pressure differential?