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
Hello, my name is Moby and I am a manta ray(Manta birostris). Despite the unfortunate nickname humans have given me, “devilfish,” I am quite a gentle and graceful giant. My wingspan can be up to 25 feet (7.6 meters) and I can weigh up to 2,900 pounds (1,300 kilograms)! The devilfish name came about as my head (cephalic) fins look like devil horns when they are curled up. But much of the time I am feeding and my head fins are unfurled to help funnel seawater into my gills. Despite my size, I only eat tiny microscopic-sized plankton that I filter through my gills. I use my gills not only to breathe, but they also act like sieves to scoop out my meals from the surrounding seawater. Although SCUBA divers often do not like cloudy water, I love it as it usually means that it is full of food for me! Because I like cloudy water full of yummy things like fish eggs, (and other spawn related products, use your imagination!) I am highly migratory. There is one species of Manta Ray (Manta alfredi), like those that live off the main island of Hawaii, that stays mainly in one area. But I like the thrill of the open ocean and I have a knack of knowing where and when fish and invertebrates will spawn.
I am a ray, which means I am related to sharks, as well as other rays like stingrays and bat rays. But, as you can see from my picture or from videos, I flap my wings and glide gracefully through the water, and I only rarely rest on the bottom. Other rays have stingers near the base of their tail, bury themselves in the sand to hide from predators, and ambush their prey. I do not have a stinger on my tail, as I rely on my speed and agility to out swim any predators, which include sharks and orcas (killer whales).
Unfortunately, my gills are not just valuable to me. Humans have begun to hunt me and my friends on an ocean wide basis mainly for our gill rakers for use in a new controversial formula used in Traditional Chinese Medicine . Sometimes, but not always, they use the rest of our bodies for cheap shark fin soup “filler.” Hunting me and my kind almost solely for my gills is so wasteful, just as hunting sharks just for their fins, or elephants just for their ivory tusks is also very wasteful, not to mention mean! A female manta ray over her lifetime will give birth to as many pups (16) as a great white shark does in a single litter (14). Great white sharks are already becoming endangered, and I hope that I do not have to worry about that too! Some countries protect me in their waters, but most of the time I am in international waters where I am not protected. Please visit Manta Ray of Hope or WildAid to see how you can help me and my kind!