When a bat star finds a food item, it extends its stomach over the prey and oozes its digestive juices onto it, liquefies the prey meal and then slurps up the resulting “soup.”Annelid worms live in the arm grooves on a bat star’s mouth (oral) side. Here the worms have a plentiful supply of leftover food bits. As many as 20 worms may live on one bat star, but they don’t harm the bat star, this is known as commensurable symbiosis. Bat stars are important as insectivores and scavengers, collecting algae and dead animals from the ocean floor and helping keep the ocean healthy.