Did you know that fish get thirsty too? Actually, they might not feel the same sensation of thirstiness that we do, but bony fish (all fish excluding sharks, rays, etc.) in the sea live in an environment in which the concentration of dissolved salts is much greater than inside their bodies.

What this means is that water will have a tendency to move from inside their bodies (lower salt concentration) to outside their bodies (higher salt concentration), particularly via the thin, permeable gill area. To replace water lost this way, marine fish need to drink. Special cells located in their gills extract and excrete excess salt in the sea water the fish take in.

Sharks and their relatives, however, don’t experience this issue to the same degree, due to the presence of organic molecules in their blood that balance out the osmotic gradient between their blood and the sea water, which means sharks may not need to drink as much as other fish in the sea.

This entry was posted on Monday, April 14th, 2008 at 9:30 pm and is filed under FiNS Fun Facts.