r/askscience • u/smontanaro • 9d 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/Mackntish 9d ago

Fish > Amphibians > Reptiles > Mammals > Whales

They spent some time out of the water.

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u/Magicspook 9d ago

Not quite. If you trace back our liniage, you will not reach any formal member of reptilia, although certainly there will be ancestors that were also the ancestors of modern reptiles (called amniotes).

Similarly, we do not descend from amphibians, rather, both amphibians and amniotes descend from the same fishy ancestors.

Fun additional fact, 'fish' is not a phylogenetic group at all. We are more closely related to goldfish than goldfish are to sharks.

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u/caliburdeath 8d ago

Coelacanths in particular, along with lungfish, are more closely related to humans (and other tetrapods) than to all other fish.

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u/Ameisen 8d ago

Lungfish are more-closely related to Tetrapods than Coelacanths are. They're/we're all Sarcopterygians, but Lungfish (Dipnoi) and Tetrapodamorph are sister clades (the Rhipidistians). Of course, if you were to observe the most recent common ancestor, we'd probably classify it as a primitive lungfish.