 About 20% of the food that has its origins in the epipelagic zone falls down to the mesopelagic zone, but only about 5% filters down to the bathypelagic zone.The fish that do live there may have reduced or completely lost their gills, kidneys, hearts, and swimbladders, have slimy instead of scaly skin, and have a weak skeletal and muscular build.Most of the animals that live in the bathyl zone are invertebrates such as sea sponges, cephalopods, and echinoderms.