Sharks, rays, and skates are part of a group of fish known as elasmobranchs. There are many ways in which I am the same as my cousins, the sharks and rays. All elasmobranchs do not have any bones. We are made cartilage, which is the same flexible material that human noses and external ear flaps are made of. Like sharks, I have a rigid dorsal fin, but mine is situated more to the rear. If you were to pet a shark (I do not recommend it!) you would immediately notice their denticles. Denticles are little teeth embedded in an elasmobranch’s skin. If you ran your hand from a shark’s head to tail, then their skin would feel very smooth. If you ran your hand from tail to head, then their skin would feel rough like sandpaper. These denticles make sharks’ bodies very streamlined so they can move quickly and quietly through the water.
Most rays have a mouth on their ventral (belly) side, and eyes on the top of their head so they can see when buried in the sand. My mouth is at the front of my body so I can open it wide to filter plankton from the seawater around me. My eyes are on the side of my head, and at the base of where my head fins are fused to my body. The length of our head fins is in proportion to how wide our bodies are.
Manta rays do vary in one special way from our shark and ray cousins, as we have the highest brain to body ratio of any of them! In fact, we have the largest brain of any fish in the ocean! It takes a certain amount of brain power to figure out where to migrate to, and to make repeat visits to those hotspots year after year. Reef manta rays need to remember where their favorite cleaning stations are! We can recognize individual divers, and we are smart enough to know when they are trying to help us, and we stay still. Often we get caught in an anchor line, mooring line, or fishing line since our head fins automatically close when brushed. I have seen, or heard stories about, many humans cutting off any line or hook stuck to a manta ray. For more information on manta rays and why we need your help, see previous blog entry on me, and visit Manta Ray of Hope