LOL...
Well, that is somewhat of a loaded question. They may or may not be the same species, but in this group, it is virtually impossible to distinguish all the species unless maybe, MAYBE, you are a seastar person specifically working on this group. But I reckon even more would be DNA comparisons. It is a mess of a genus, highly polymorphic - it varies a lot in number of arms, size and color. The number of arms is not likely age dependant. Though sometimes there are genetic "errors" in certain species of stars (eg it is not uncommon to find a Linckia with 4 arms now and then...or another species where there was an error in regeneration of the arm...I'll have to find pictures...) overall the individual will have the same number of arms or arm "potential" through its life I would think. So when an arm buds off, I suspect it will grow back the 7 arms if all goes right.
In other cases we would say that the number of arms is a species characteristic. There are few, as an example, brittlestars with 6 arms and this is usually quite consistent, just as "most" seastars are known to have 5 arms. But in other genera, such as Asterina, that number is not reliable as a species characteristic...which may be a characteristic in and of itself (if that makes sense).
We sometimes cling, as seastar and ophiuroid people, to a few characters and every once and awhile something comes along to really mess with that idea. I had situations where one individual animal could be simultaneously placed in 3 genera based on the primary characteristic of that genus. It tends to mean there is something screwy going on...but it is nonetheless frustrating. I think nearly any seastar expert would call Asterina frustrating.
