Feet. It's probably not something you think about a lot (unless you are a podiatrist... or maybe really like shoes), but feet are actually very cool. Sure they get us moving about, but across the animal kingdom, there are many different feet in all sorts of shapes and sizes. If there was an award for weird feet in the world, sea stars would probably be up top.
A sea stars feet are very very different to ours. First is the amount. We have two. Sea stars can have hundreds. Which makes sense if you think of it. We stand upright to walk whereas sea stars are flat, and crawl about. Hundreds of feet probably wouldn't help us very much. Then is their appearance. Their feet are tubes…
Tube feet are pretty awesome (if you are a sea star anyway). They would by hydraulic pressure made possible by a water vascular system. The system is a little complex, but essentially the sea star takes in water through a little structure on its back called a madreporite which is then pumped around its body via canals which connect to the tube feet. By 'pumping' the water they can expand and contract these tube feet - and do something super-neat… these feet can suck. Sure, they move super-slow but… sucky feet!
Sucky feet is a very nifty feature for a sea star. It helps them grip onto surfaces - even when water movement is strong. They're also used to hold down prey like sea snails as they move them towards their stomach - which by the way comes out of the sea stars mouth to digest it! Gross? Yes. Cool? Incredibly.