Starfish (along with most other echinoderms as far as I’m aware) indeed show pentameral symmetry, usually, so at least multiples of 5. I don’t know what mechanisms cause individuals to differ from this (probably mutations or “faulty” regeneration), but I’ve also seen essentially 4 armed “squarefish” in the past.
The two most unusual organisms I’ve seen are:
This Campanula persicifolia that also differed from the standard symmetry of this species in a really cool way. (Interestingly only the topmost blossom on each stem was affected).
When I saw it, it immediately kept my eye -for what reason?
True, i never had seen it before because it is very uncommon in my region, but however said to be not uncommon in the eastern part of Europe.
But there is something else. It is called seven-star because it has seven petals.
Most flowers have petal numbers matching the mathematical fibonacci series or -if sepals count too (Orchids and Lilies) a fibonacci number times two.
But the number seven matches neither the first nor the second condition.
How comes?
Is it a neophyte from the stars that was simply overlooked ?