What is a Cleanser Wrasse in the Mouth of a Potato

Question

What is a cleanser wrasse in the mouth of a potato cod an example of?
A) trophic interaction
B) mutualism
C) neutral interaction
D) coevolution

Accepted Answer

Mutualism is the correct answer because the cleanser wrasse benefits by getting food (usually parasites) from the mouth of the potato cod, and the potato cod benefits by having parasites removed, improving its health.