Depth Limits - Why are animals different?

[archman]

I think the deepest divers are the elephant seals... 5000 ft. is not uncommon and I believe they've been tagged deeper than that.

Yeah, elephant seals smoke sperm whales most of the time, but they're all about vertical movement around fixed coastal sites, whereas cetaceans like to swim in other ways (i.e. horizontally). As for the Weddell, it's supposed to have the best developed physiology for deep diving, even if it's native sea is fairly shallow. Something about muscle fiber typing and dissolved gas percentages. One of my friends just got her PhD in pinniped physiology, and sections seal muscle for kicks. I wonder if they use a meat slicer...

 

[H2Andy]

seal hamburger... yummy

 

[archman]

seal hamburger... yummy

I can only comment on seal soup (which one of my girlfriend's sampled in Alaska), but she said it was pretty nasty. I suppose it's an acquired taste, like the creme soda I'm sipping. I do it to freak my students out.

 

[glbirch]

I can only comment on seal soup (which one of my girlfriend's sampled in Alaska), but she said it was pretty nasty. I suppose it's an acquired taste, like the creme soda I'm sipping. I do it to freak my students out.

What's wrong with creme soda? I've always liked it...

 

[Cave Diver]

My question is...How can dolphins and whales dive to incredible depths while scuba divers are restricted to the near surface waters? Does anybody know?

Because they are not breathing compressed air.

 

[mbuff]

but they're all about vertical movement around fixed coastal sites, whereas cetaceans like to swim in other ways (i.e. horizontally). As for the Weddell, it's supposed to have the best developed physiology for deep diving, even if it's native sea is fairly shallow. Something about muscle fiber typing and dissolved gas percentages. .

I don't know a lot about marine mammals in general or Weddells in particular but what you say about muscle fiber type resonates. I remember something unusual about their myoglobin...

With respect to elephant seals, they actually don't spend their diving time around fixed coastal sites... approximately 9 months a year are spent at sea with no return to land until breeding season. As I understand it, once they park on the beach they're there for the duration. I seem to remember two types of dives from their at sea time: long shallow descents, which were attributed to sleeping behavior and steeper dives, which are attributed to foraging/feeding behavior.

Heck of a way to nap.

 

[archman]

Where/how do seals sleep if they don't return to land? And why don't I know the answer to this? crud.

 

[H2Andy]

got the following from here. use at own risk:

Although harbor seals prefer to sleep on land, they often sleep in the
water. They can sleep underwater, though they then have to wake up
frequently and regularly to surface and breathe. So, this is not something
subconcious, but something they have to conciously do.

Harbor seals sleeping on the water's surface often assume a posture known as
bottling: most of the seal's body remains submerged, but the animal's face
pokes above the surface like a snorkel, allowing the animal to breathe
regularly while sleeping or resting. Elephant seals sometimes rest in the
water in a similar manner. Northern elephant seals may possibly sleep
hundreds of meter underwater. Walruses can inflate pouches in their throat
which can help them float at the water's surface as they sleep. From studies
of sleep in grey seals, we know that grey seals have REM sleep
(rapid-eye-movement; lightest stage of sleep, in which brain-wave activity
is highest and dreaming takes place) which does not occur in all animals,
and it doesn't take place when pinnipeds during underwater sleep. It does
take place when pinnipeds sleep at the surface of the water and on land.

Looking at an older reference that had some information on seals and
sleeping, I found that Galapagos sea lions may doze in the water for a few
seconds, but remain alert even then. Fur seals have been seen sleeping at
the water's surface on their back or sides. Captive sea lions and some seals
can sleep underwater.

 

[glbirch]

I don't know a lot about marine mammals in general or Weddells in particular but what you say about muscle fiber type resonates. I remember something unusual about their myoglobin...

Not sure if this is what you are thinking of but I mentioned earlier in this thread that some diving mammals, Sperm Whales being a notable example, have levels of myoglobin in their muscles up to ten times higher than we do. Makes the muscles look almost black in color. Gives them a certain advantage in the diving department as it allows for storage of much greater levels of O2 than we ever could.

 

[mbuff]

Where/how do seals sleep if they don't return to land? And why don't I know the answer to this? crud.

I don't know about seals in general, but northern elephant seals sleep in a shallow decent dive while out at sea. (when I speak of elephant seals, I'm referring to the northern elephant seal, not the southern...)

Thanks for the reminder about myoglobin content in sperm whales, glbirch. I had remembered that there was something about myoglobin in elephant seals as well, from an intro physiology class (taught by an elephant seal guy at UC Santa Cruz.)