Problem
The louse Cymothoa exigua lives inside the mouth of certain fish. It attaches to the fish's tongue, strangling it until it falls out. Once the tongue falls out, the louse functionally replaces it. Generally, this is thought of as a parasitic relationship.
What criteria would need to be met for this relationship to be considered parasitic? Is it possible that this relationship could be an example of mutualism or commensalism? Use what you have learned to classify this relationship and explain your reasoning.