Skates are marine animals that glide across the ocean floor. These cartilaginous fish are closely related to sharks and rays, sharing a common ancestry within the class Chondrichthyes. Skates represent a diverse group, encompassing over 150 described species, and play a role in various ocean ecosystems. They thrive in a wide range of marine environments, from shallow coastal waters to the deep sea.
Identifying Skates
Skates possess a flattened, disc-like shape that can be rounded or diamond-shaped. Their broad pectoral fins are fused to the sides of their heads, creating a continuous, wing-like appearance that aids movement across the seabed. Like sharks, skates have skeletons made of cartilage rather than bone, which contributes to their flexibility. The skin of many species is rough, covered in small, tooth-like structures called placoid scales or dermal denticles, and some also feature thorny or spiny projections on their backs and tails.
On the underside of a skate’s body, their mouths and five pairs of gill slits are located ventrally for feeding and breathing while resting on the ocean floor. Eyes are positioned on the dorsal, or upper, side of their heads, with spiracles just behind them. Spiracles enable skates to draw in oxygenated water for respiration, even when partially buried in sediment, preventing them from inhaling sand. Unlike many rays, skates have a fleshy tail that lacks a stinging barb, and they possess two small dorsal fins usually situated near the tail’s tip.
Skate Life in the Ocean
Skates are bottom-dwelling creatures, found resting or moving along the seafloor. Their habitats span a wide range of depths, from the intertidal zone to over 3,000 meters. They are globally distributed, inhabiting cold and temperate waters, and some deep tropical regions. Skates are particularly diverse in higher latitudes and deep-water environments.
As carnivores, skates feed on bottom-dwelling invertebrates. Their diet includes crustaceans such as crabs and shrimp, mollusks like clams and oysters, and small fish. Skates use grinding plates in their mouths to crush the hard shells of their prey.
They are oviparous, meaning they lay eggs. These eggs are encased in leathery structures called “mermaid’s purses.” These oblong egg cases are laid on the ocean floor and often have tendrils that anchor them to the sediment or seaweed. The embryos develop inside these cases for several months before hatching.
Skates Versus Rays
While skates and rays are often confused due to their similar flattened bodies, several distinctions set them apart. A primary difference lies in their tail structure. Skates have thicker, fleshy tails without the stinging barb found in many ray species. Many rays, in contrast, possess whip-like tails equipped with venomous spines for defense.
Reproductive methods also differentiate the groups. Skates lay encapsulated eggs, known as “mermaid’s purses.” Most rays are viviparous, giving birth to live young. Body shape also differs; skates have a rounded or diamond-like disc shape, while many rays exhibit a kite-like form. Skates are largely harmless to humans unless provoked or handled improperly.