The majestic, wing-like manta ray is classified as a fish, not a mammal or another type of marine life. Their immense size, graceful movement, and distinct body shape often lead to confusion about their place in the animal kingdom. Despite their difference in appearance from a typical fish, like a salmon or a tuna, manta rays are definitively fish. Their biological classification places them firmly within the group of aquatic, gill-breathing vertebrates.
Manta Rays Belong to the Fish Class
Manta rays are formally categorized as vertebrates, possessing a backbone and placing them within the Phylum Chordata. They are classified under the Class Chondrichthyes, which encompasses all fish with a skeleton made primarily of cartilage. This biological detail determines their identity as a type of fish, despite their flattened, diamond-shaped bodies.
Their taxonomic hierarchy continues with the Order Myliobatiformes, commonly known as the rays and skates. This order includes species like stingrays and eagle rays, all sharing a body plan with flattened pectoral fins fused to the head. Manta rays are highly specialized fish that evolved a unique form for their open-ocean, filter-feeding lifestyle.
The Defining Feature: Cartilaginous Skeletons
The feature separating manta rays from most other fish is the composition of their internal support structure. Unlike bony fish (Class Osteichthyes), the manta ray’s entire skeleton is made of cartilage, the flexible tissue also found in human noses and ears. This cartilaginous structure provides a lighter, more pliant framework, contributing to their agility and ability to “fly” through the water column.
As cartilaginous fish, manta rays lack a swim bladder, the gas-filled organ bony fish use to regulate buoyancy. Without this control, they must constantly move to avoid sinking, which is also necessary for their unique method of breathing. Most bony fish pump water over their gills using an operculum, but manta rays must swim continuously to force oxygenated water over their gills, a process known as ram ventilation.
The absence of an operculum means their five pairs of gill slits are visible externally. This constant movement is a direct consequence of their skeletal biology, dictating both their buoyancy and respiratory needs.
Close Relatives: Sharks and Skates
Manta rays share the Class Chondrichthyes with other rays, skates, and all species of sharks. All members of this class belong to the subclass Elasmobranchii, sharing a deep evolutionary history and several defining physical traits. Besides the cartilaginous skeleton, other features solidify their kinship.
One shared feature is their skin, which is covered in tiny, tooth-like structures called placoid scales, or dermal denticles. These denticles give the skin a rough texture and help reduce drag as the animal moves through the water. Additionally, like sharks, manta rays possess five to seven exposed gill slits, lacking the protective bony covering found on most fish.
Their reproductive strategies also align with those of sharks, involving internal fertilization rather than the external spawning common among bony fish. Manta rays are generally ovoviviparous, meaning the eggs develop and hatch inside the female before she gives birth to live pups. Although skates lay eggs in protective cases, internal fertilization is a common bond across all elasmobranchs.