According to a study recently published in the journal Ecology, cusk-eels (family Ophidiidae) are congregating deep underwater among tubeworm thickets near a methane seep in the Atlantic Ocean. The fish appear to favor the locale not for the sights, but for their neighbors—tiny spider crabs that feast on the animal’s parasites. Red cusk-eels embedded in a tubeworm bush at a methane seep off central Chile. Video footage also showed spider crabs near the fish engaged in what appeared to be parasite cleaning. Levin, Soto, and the others also noted a peculiar detail—this appeared the only mound that appealed to the red cusk-eels.