One of my favorite finds from our trip to #Oahu, an Indo-Pacific Rock-Boring Urchin (Echinometra mathaei). I’ve never seen an urchin in real life outside of an aquarium and was completely starstruck. They use their spines and teeth to bore into and hold onto calcerous and basaltic rock. At night, they emerge from their hollows to graze on algae. As pretty as they are, they can cause damage when imbalance (humans) strike.
Because of their boring, they are a source of bioerosion of reef rock, and in areas where their natural predators are overfished or otherwise removed, their populations can grow tremendously, thereby causing more damage.
But to end on a slightly more fun fact, a super tiny commensal shrimp, Athanas areteformi, lives among the spines of this sea urchin. They’re like best buds!