Assuming that this is a serious question, a mango is a tropical fruit about the size of a human fist. That means that these single cell organisms are huge, as one normally thinks of single cell organisms as being, literally, microscoopic, i.e. only visible in a microscope.
“...a mango is a tropical fruit about the size of a human fist...”
I know, just my flippant comment and point being that,
a more logical comparison would have been to the size of a fist.
Why, of all things, would someone compare something to the size of a mango?
Certainly not the first thing that would come to most folk’s mind.