This second hinge allows their mouths to open from side to side. Green morays have very sharp teeth and each eel has an additional row of teeth in the roof of its mouth. It may sound strange, but the eels need these teeth to catch and eat their prey. Moray eels also constantly open and close their mouths, displaying those sharp teeth. This biting motion may appear to be an aggressive behavior, but it is actually the way the eels breathe.
Water enters through the eels' mouths and is propelled over their gills by the biting motion.
The water is then expelled through small holes, called spiracles, on each side of the eel's head. Although the Aquarium's morays appear green, their skin is actually dark blue in color. However, the eels are covered with a layer of yellowish algae-containing slime that causes them to appear green. These eels can also look brown, gray or gold, depending on the type of algae living in this slime. Their long, lithe bodies, dorsal fins and mouths full of needle-sharp teeth give these nocturnal hunters their place at the top of the food chain.