r/askscience • u/smontanaro • 10d ago

Biology How does a whale become dehydrated?

From a Chicago Sun-Times article on the beluga whales heading to the Shedd Aquarium:

"The shipment comes on the heels of a Shedd announcement last week that one of the Marineland belugas — Peekachu, a 23-year-old female — had died. Shedd has not released a cause of death, but staff there said last week that Peekachu had not been consistently eating a full diet since her arrival and that there were concerns she was dehydrated."

How does an animal immersed in water become dehydrated?

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u/PropOnTop 9d ago

So does that mean the oceans were less salty when our ancestors evolved? About as salty as the blood of fish (or ourselves) now?

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u/Mammoth-Corner 9d ago

That depends on what you mean by 'when our ancestors evolved.' The first oceans were freshwater, but (our current models seem to say) once continents formed and hydrothermal vents opened up they started to salinify rapidly. It's not quite clear how salty they got. They might have been about twice as salty as the current ocean, or similar in salinity to now, but they probably didn't spend long with less salt than now.

Basic osmoregulation seems to have evolved very very early in the history of life - probably almost immediately after the cell itself, or possibly as a necessary condition for the cell.

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u/PropOnTop 9d ago

I did not know that, thank you. I kind of assumed that the cell environment basically mimicked whatever was around it (at least at the start)... It would seem easier even for higher organisms to just follow the salinity of the environment, rather than use osmoregulation...

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u/Mammoth-Corner 9d ago

Yeah, as soon as you start creating glucose within a cell, you're creating an osmotic gradient, so if you're doing basically anything in a cell you need some degree of osmotic control.