How do marine mammals control their salt intake?

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Miguel Navarro

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How do marine mammals control their salt intake?
« on: 22/05/2009 12:30:02 »
Miguel Navarro  asked the Naked Scientists:
Hi Dr. Chris and everyone at The Naked Scientists!!
Got another little question for you, this one about marine biology. I was wondering how do marine mammals (and all sea animals for that matter) like whales and dolphins manage to get rid of the extra salt in the water that they drink, if they actually drink any. I heard that if you drink sea water it actually dehydrates you because the salt in the water will trigger osmosis at the cellular level or something like that. So how do they manage to survive this?
By the way, things are looking better now here in Mexico with the H1N1 flu virus, probably the economic effects will be the worse part besides from the loss of lives of course.
That's all from your fans here in Mexico, keep up the good work!
Miguel Navarro Gamboa

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Offline JnA

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How do marine mammals control their salt intake?
« Reply #1 on: 08/06/2009 01:56:33 »
Whales don't drink the salt water (for the most part), instead they get their supply from the organisms they eat. Some of their food (eg the plankton favourite dish of baleen whales) has a very high salt content though the whales kidneys are many times more effective than our own and they can produce urine with a much higher concentration than sea water itself. The more concentrated the urine the greater the amount of freshwater the animal can gain.
The amount of water needed for a marine mammal is probably less than one imagines since they have very little to no 'sweat' loss. There is some respiratory evaporative loss, but whales employ what is called apneustic breathing. Which basically means they breathe periodically. This allows for a greater O2 exchange and lower respiratory evaporation.

Most fish drink the salt water and eliminate the salt through their gills.



Offline thedoc

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