Is There a Parasite That Can Replace Your Brain?

Tongue eating louse is the only known parasite that can totally replace an organ in another creature. It's up of eight muscles, which i did not know. And by assuming loant talk to each other, is there sit symbiotic was cthat he took one of my fish gat in i of damn you, jay? So in fact, the parasitic tongue doesn't make that much of a difference and the fish doesn't seem to mind.