saltwater
dr. dolittle | July 12, 2016 Image of a Gulf toadfish, Opsanus beta, from Wikimedia Commons
Teleost fish living in saltwater environments are constantly compensating for water loss. This happens because their surroundings have higher concentrations of salts than their plasma and the rule of thumb in Biology is: water follows salt. Thus these fish must somehow compensate for water loss in order to prevent dehydration. One way they do this is by drinking a lot of water. Ions are then removed from the water in the intestines which creates a gradient for water absorption into the body. A new study published in the…