There is a difference between self-awareness and sentience.

At least two cats are self-aware. This spider seems to be self-aware: https://www.youtube.com/watch?v=Ij4pdf49bxw (Note that it discovers that the mirror image has something to do with itself, then apparently tries to verify experimentally that this impression is indeed the case. The motives are unknowable, but drawing conclusions from my own inner life, I'd venture to say the spider finds the phenomenon interesting.)