Manta rays, Manta birostris (Indian Ocean) and Manta hamiltoni (PacificOcean), are among some of the most graceful and wondrous creatures of the sea. Reaching lengths of up to 6m, manta rays are in the 5% of elasmobranches (sharks and rays) that grow to lengths of over 4m, and havebeen measured to 9.1m!

Manta rays are placed in the same category as sharks, in the cartilaginous fishes, or class Chondrichthyes. Of the order Rajiformes, there are 12 families, containing over 450 different species. The Manta ray is the largest. Mobula rays are often mistaken for manta rays. They are in the same family–Mobulidae–and are often called devil rays. However, mobula rays only reach lengths of around 1 to 2m, and usually travel in larger groups. Manta rays do not have a swim bladder, but instead have an oil-filled liver.

Unlike fish, which achieve buoyancy by adjusting an air bladder, manta rays must continue to swim. If they were to rest, their weight would make them sink to the bottom.Manta rays also have skeletons made of cartilage instead of bone, which gives them flexibility and helps to reduce their overall weight. Using their cephalic fins (the two fins attached to their head) manta rays will circle their prey, causing them to cloud together in one large mass.

Swimming in a loop, manta rays will barrel roll in order to maximize their plankton intake.In order to rid themselves of dermal ectoparasites they jump high out of the water. Manta rays that continue this behaviour could also just be at play, or performing a mating ritual. Pregnant females jump out of the water as they eject their young into the ocean.

The dorsal sides (topsides) of Mantas are usually black with patches of white near the head and fin tips. When a predator is swimming above, its coloration blends in with the colour of depth of the water around it. The ventral side (bottomside) of a Manta is usually light with a few dark patches. This allows them to often go undetected by predators that swim underneath them because their white bellies blend in with the ocean’s surface.Scientists distinguish individual Mantas by identifying the dark spots on the underside. These spots increase in number with age.

While working as a full time Divemaster in Hawaii, Anik Clemens also worked part-time at a Microbiology Lab affiliated with the University of Hawaii. She can be contacted at anikclemens@yahoo.com