Well, sort of. Some species used magetic fields for navigation, but this is primarily long-distance migrators like sea birds.Originally Posted by [b
However, crustaceans (among other marine inverts) use something called a statocyst to detect gravity. Essentially, it's a little hollow ball with sensory cillia on the inside and a grain of sand (which they take in while molting). The grain of sand presses down on the cillia that are "down", and the animal uses this to determine which direction gravity is pulling.
What you refer to is when you put a crustacean in a tank filled with iron filings before it molts, meaning it will take up the iron for use in the statocysts. Once this is done, you can use a magnet to make the crustacean think gravity is pulling in any direction you want. I'm actually planning on making use of this trick for some experiments on crab locomotion someday.