Can starfish tolerate fresh water?

Starfish live in salt water, and their bodies have the same salt content as ocean water. Varying salt concentration in the water can be a lifethreatening challenge to a starfish. If there is less salt in the surrounding water than in the creature's body fluids, its cells might burst.

This is due to osmosis, which means that water will always balance areas with different salt contents. In salt water, there is osmotic equilibrium, as the salt concentration is the same on both sides of the starfish’s cells. Equal quantities of water pass in and out of the cells. In fresh water, there is no equilibrium, as the salt concentration is higher inside the cells than in the

surrounding water. So, water seeps into the cells, and they could burst.

Unlike fish, starfish have no osmosis regulation, and consequently, long periods in fresh water could be fatal.

If a starfish is left in fresh water, it will die, as its cells burst.