Yellow Spotted? - Lincoln Park Zoo Poem by Ima Ryma

A yellow spotted Amazon
River turtle, my naming be.
But my yellow spots are long gone,
Since I came in '73.
Back then 'twas just a turtle lad.
The yellow spots do fade with age.
Not having them is not so bad.
Of course when I take center stage,
Inquiring humans read my name,
Then find me spotlessly nearby.
I do enjoy playing the game -
Don't spot the spots and don't know why.

The puzzled question's heard a lot -
So why no yellow spots to spot?