Stars typically do not clone in captivity although there have been rare instances of it happening. If you attempt to do it it you likely will not only lose the leg you cut off but kill the star in the process. In the wild they can clone from any part of their body - not needing any mouth portion.
i have never in all my years of college heard of a starfish regenerating a new body....appendages yes clones no...some will need to post a link for me to see the proof
In the invert tank at an LFS I worked at, we had a red linkia leg wandering the tank for a day ( at least my shift). But didn't see it the next, so would say thats a no for linkia.
I know for a fact it works with the little astrina stars. I see them in sections and growing new starfish all the time. Not sure I'd try it with a large star though. Atleast not the reef ones. Maybe a brittle or serpent, or even chocolate chip.
This dose happen as stars are very simple creatures they are basicly a living moving type of coral lol. They actually have no brain (I know im gonna ketch hell for saying that but its true). And they can in fact clone but I dont know how possible it be in the home aquarium. Kinda like a the cucumber it expells its organs to scare off fish in the wild it can regrow these but in the aquarium most likely ya have a dead cucumber lol.
I have to agree with what others have said. Not something you want to do in an aquarium. Most stars don't do well in tanks when they're intact, I doubt they'd fair any better in pieces, and would probably get an infection.
-Justin
A friend of mine recently rebuilt his tank setup and accidentally took a leg off a brittle star - this was approx. two weeks ago - the leg is still moving around in the tank - I don't think it is possible for it to clone in a captive environment - but I will certainly keep an eye on this one.