"The turtle does not read."
Translation:La tartaruga non legge.
legge is 3rd person singular (informal) of the infinitive leggere.
Here is a conjugation table:
If you meant about the formal version, my understanding is it would take 3rd person singular, but it only means you (singular, formal), so that wouldn't work for talking about our friend the turtle's reading habits.
My dictionaries both give testuggine as the preferred translation for "Turtle" and tartaruga for "Tortoise". Tartaruga del mare is given as an alternative for turtle. But mine are "English" dictionaries, rather than American English.
Duolingo has been going long enough to cope with this. How about a course for English speakers and Americans to learn each others languages?