Whales and Dolphins get the bends?

[DrSteve]

http://story.news.yahoo.com/news?tmpl=story&cid=585&e=3&u=/nm/20031008/sc_nm/science_dolphins_dc

OK I've not read the actual Nature article. But this is why I think the above story is a POS...
1. When we come to the surface slowly we are exhaling extra N2 as it is purged from our body tissue.
2. If a dolphin etc., has a full breath they go down, N2 gets absorbed. When they surface the volume in their lungs expands again but they have no desire to exhale (or do they?) as they hold their breath. Even if they did exhale they would only be removing air which has expanded in the lungs.

Now sonically induced bubble formation I can believe - see it all the time with the sonicators at work...but just based on how quickly they surface? It just sounds like BS to me...but I'd be happy to be proved wrong.

 

[JHAM]

I have to admit, it sounds pretty far fetched.

 

[pasley]

"It is widely accepted that there is a link between naval sonar use and mass strandings, predominately of big whales; what hasn't been fully understood is what the mechanism would be," Jepson added. "

I don't know about that. I know it is a theory, but I do not believe it is widely accepted. Yet the article accepts it as fact.

Sounds like an agenda article to me and not a lot of science behind it.

 

[BIGSAGE136]

http://www.newscientist.com/news/news.jsp?id=ns99994254

If this isnt credible its as close to the scientific knowledge on this
subject matter we'll get without some heavy research.

 

[Babelfish]

I read in a Honolulu Star article several years ago that said whales sometimes beach themselves when they feel very sick. Perhaps the sonar makes them feel sick, like people do when they get nitrogen narcosis?

 

[anth]

My understanding (as an undergrad marine biology student) is that marine mammals have very little nitrogen loading th the first place. My experience is primarily with pinnipeds, but these adaptations show up in other marine mammals as well. Deep-diving mammals do not really hold their breath - they exhale gas from their lungs before diving, aided by a hinged rib cage that allows remaining air in the lungs to move from lung extremities to the middle of the lungs to a cartiliginous area where little gas exchange takes place. To compensate for not having any air in lungs, they have much more hemoglobin and myoglobin to store oxygen than you or I - look at their blood during a necropsy, it's DARK. That's one of the mechanisms which protects them from DCS, narcosis, and ox tox (no air in lungs)... if anyony has any questions about this I'd be happy to help, although I'm sure there are others ont the board more informed than myself.

DSAO,

Anth

 

[DrSteve]

Thanks for your response. What you said pretty much proves the point - no whales or dolphins are going to get bent. Shows just how carefuly you have to read between the lines of any science article, but especially one which is written for a general educated readership than a specialised one.

 

[BIGSAGE136]

Seals, and their close cousins have a much different metabolism.
Whales do lock their oxygen in at the surface and dive with little air in the lung cavity to help them submerge. They can do this because of their ability to carry high concentrations of o2 in their hemoglobin.

The additional info that might be helpful is in the web links. Also
it might be of some insight to read about cavitation technology
and its latest applications. There is some significant cross over
and IMHO items that should be given serious consideration before any summary conclusions are put forth about the validity
of the article or its intent.

 

[The Iceni]

Take a look at this thread.

 

[Dr Deco]

Dear Scuba Board Readers:

”Does he know Cornwall, who only Cornwall knows?”

If you are acquainted with only one aspect of a subject, your views may not be encompassing enough to fully assess the situation. The writers of the paper in the journal Nature were describing aspects of a problem better understood in land mammals than marine mammals and counting them as equal.

This is not unlike the situation that prevailed over a couple of decades when research on DCS in rats was applied to humans with respect to biochemical mechanisms. The disorder has similarities but it is not identical in the different species.

I was not a reviewer of this paper. I will not go so far as to say that it had more errors than a ’62 New York Mets game, but…

Problems

• There is always the association between the presence of gas bubbles and “the "bends". A large proportion of divers today know that many people will have Doppler-detectable bubbles in the blood following a dive but will not have DCS. The simple finding of gas bubbles in the tissues of the cetaceans is not evidence that they had DCS.
• The gas phase that was reported appeared in the liver. I am not certain why this organ was picked, as I have never studied it and it does not play a large role in DCS.
• The relationship between cavitation from sonar and the increased tendency to form a free gas phase is not strong. The devices do not form micronuclei but rather cause the growth of preexisting nuclei by rectified diffusion and the streaming of the fluid in the neighborhood of the nuclei. This occurs in vitro but whether it happens in vivo is not known.

Dr Deco :doctor: