Sea Urchin's
Sea urchins are small, spiny, spherical organisms that live in a marine environment. Sea urchins have 5 gills around the mouth. Their tube feet behind the spikes also serve as means of respiration. Sea urchins are one of the few echinoderms that resemble the the respiration of a fish.
Sea Urchin's Respiration
Sea urchins possess five pairs of external gills, located around the mouth. This is the main form of respiration for sea urchins'. They also can use their tube feet at respiratory organs and are the primary sites of gas exchange in heart urchins and sand dollars, both of which lack gills.