A Group of Biologists Are Studying an Interaction Between Coral

A group of biologists are studying an interaction between coral and three species of crab (crab 1, crab 2, and crab 3). They discover that all three species of crab benefit from the coral by feeding on lipid-rich coral mucus. They conduct an experiment in which they remove each species of crab from the coral and then measure the extent to which the coral were overgrown by noxious algae. Based on the data in the figure, explain whether or not each of the three crab species is a mutualist with coral.