Stingrays are a group of cartilaginous fish easily recognized by their disc-like bodies with large, wing-like pectoral fins. They belong to the suborder Myliobatoidei within Rhinopristiformes, an order of rays. These fish have a long tail equipped with a venomous spine or stinger, a feature that distinguishes them from other rays. While they may seem intimidating, stingrays are not aggressive, stinging only when provoked.
Scientific Classification
Animalia
Chordata
Chondrichthyes
Myliobatiformes
Scientific Classification
Animalia
Chordata
Chondrichthyes
Myliobatiformes
In total, there are currently about 220 known stingray species divided into 8 families: sixgill stingrays (Hexatrygonidae), deepwater stingrays (Plesiobatidae), stingarees (Urolophidae), round rays (Urotrygonidae), whiptail stingrays (Dasyatidae), river stingrays (Potamotrygonidae), butterfly rays (Gymnuridae), and eagle rays (Myliobatidae).
Stingrays (Types and Species)
Types
Given below is a list of some of the most common species of stingrays found worldwide. They have been grouped based on their habitats.
Size: Most stingrays have disc widths of 1 to 3 ft (0.3 to 1.0 m), with total lengths (including tails) often reaching 3 to 7 ft (1 to 2.1 m).
The largest stingray, the giant freshwater stingray (Urogymnus polylepis), measures up to 7.2 ft (2.2 m).
Weight: Most species weigh between 11 and 165 lb (5 and 75 kg). However, the giant freshwater stingray can exceed 660 lb (300 kg) in weight.
Body and Coloration: These fish have disc-shaped, dorsoventrally flattened bodies with large, wing-like pectoral fins that merge seamlessly with the head. Their eyes are located on the top of the head, while the mouth is on the ventral side. They also have a long, whip-like tail, equipped with one or more venomous stingers (also called spinal blades or barbs), depending on the species.
They have small openings called spiracles behind their eyes. These spiracles help stingrays breathe when they remain buried in the sediment while waiting for their prey and cannot respire through the usual mouth-to-gill pathway.
These fish have flat, plate-like teeth, which are modified placoid scales that are regularly shed and replaced (polyphyodonty). They also have a holostylistic jaw suspension, where the mandibular arch of the skull is suspended by an articulation with the hyomandibula. This suspension allows for the independent mobility of the upper jaw, which can also be protruded outward.
Depending on the species, the dorsal side of stingrays is brown, gray, olive, or sandy. Such coloration, along with mottled patterns in some, helps these fish camouflage effectively against the seabed. On the other hand, the ventral side is typically white or light-colored (counter-shaded), reducing visibility from predators swimming beneath them.
Blue-Spotted Ribbontail Ray
Cowtail Stingray
Distribution and Habitat
Most stingrays are found in coastal tropical and subtropical marine waters around the world. Some species, such as the thorntail stingray (Dasyatis thetidis), occupy warmer temperate waters, whereas others, like the deepwater stingray (Plesiobatis daviesi), live in the deep ocean. Some stingrays, like the river stingrays, are found exclusively in freshwater environments.
Although most species are demersal, occupying the water column near the seabed, some, such as the pelagic stingray (Pteroplatytrygon violacea), are pelagic, living in the open ocean.
Diet
They are carnivorous, typically feeding on crustaceans, mollusks, marine worms, and, occasionally, small fish.
Behavior
Unlike most fish that propel themselves forward using their tail fin, stingrays use their paired pectoral fins for swimming. Bottom-dwelling stingrays typically ripple the edges of their fins, creating multiple small waves (undulatory motion) that push water backward and move the animal forward. In contrast, stingrays that live in open waters usually flap their fins up and down, producing large, powerful strokes (oscillatory motion).
Benthic stingrays are ambush predators that stealthily wait for their prey to approach them. With their pectoral fins pressed against the substrate, they raise their heads, generating a suction force that pulls the prey under their bodies (tenting). They then crush the prey with their powerful jaws and consume it.
Since their eyes are located on the top of their heads, these fish cannot see prey hidden in the sediment. Instead, they sense electric fields generated by these prey using sensory pores called the Ampullae of Lorenzini located around the head and the snout.
Lifespan
Stingrays typically live between 15 and 25 years in the wild. However, in captivity and under impeccable care, some species have been recorded to survive up to 30 years, though such instances are rare.
Fantail Stingray
Round Stingray
Reproduction and Life Cycle
During the breeding season, most males sense electrical signals given off by mature females using their Ampullae of Lorenzini. On finding a suitable mate, the male tries to court her, following her closely and biting at her pectoral disc. He then tries to mate by placing one of his two claspers into her valve. The general aggressive behavior of male stingrays during the mating phase is attributed to the rise in androgen levels.
These fish are ovoviviparous, meaning the females give birth to live young, typically between five and thirteen, depending on the species. The gestation period of stingrays varies between 3 and 12 months.
The embryos derive nutrition from the yolk sac. When the sac is depleted, the mother provides nourishment through uterine secretions (uterine milk). There is no placental connection between the mother and the embryo.
The young are born with instinctual abilities to protect and feed themselves, and they usually swim away from their mothers. Only in a few species, such as the giant freshwater stingray, do the mothers let their babies swim with them till they are about one-third their size.
Predators
Stingrays are primarily hunted by sharks, especially hammerheads, bull sharks, and tiger sharks. They are occasionally preyed upon by killer whales and elephant seals. Some large bony fish, such as the giant sea bass (Stereolepis gigas), may opportunistically feed on stingrays, particularly juveniles.
Southern Stingray
Stingray Fish
Interesting Facts
These rays are generally not aggressive. However, they may attack humans with their spines when provoked or stepped on. An injury inflicted by stingrays typically causes local trauma, including pain, swelling, and muscle cramps, though it may be life-threatening if the spine punctures a vital organ.
Unlike other venomous animals that store their venom in some glands, stingrays store their venom within tissue cells, particularly in secretory cells of the vertebral column. The venom has been found to contain toxins, such as cystatins, peroxiredoxin, and galectin.
