Skates are marine creatures with a distinctive appearance. These fish, with their flattened bodies, are bottom-dwellers. While they might appear similar to their ray relatives, skates possess specific characteristics and a life cycle that set them apart.
Identifying Skates
Skates are cartilaginous fish, meaning their skeletons are composed of cartilage rather than bone, similar to sharks. Their large, wing-like pectoral fins extend along the length of their bodies, from the snout to the base of their tail, and these fins are used for propulsion through the water. Many species of skates have thorn-like structures or prickles covering parts of their dorsal (upper) surface, which offer a form of protection.
A distinguishing feature of skates is the presence of two small dorsal fins located towards the end of their tail. Unlike some rays, skates do not possess a stinging barb on their tails, making them harmless to humans. Their eyes are positioned on the top of their heads, while their mouths and gill slits are located on their underside, an adaptation for feeding on benthic organisms.
Skates Versus Rays: Key Distinctions
Several features distinguish skates from rays. One primary difference lies in their tail structure. Skates have thick, fleshy tails that often feature two small dorsal fins and lack a venomous spine. In contrast, most rays possess whip-like tails that frequently have one or more venomous stinging spines used for defense.
Reproductive methods also serve as a clear differentiator. Skates are oviparous, laying eggs encased in a protective, leathery “mermaid’s purse” on the ocean floor. Most rays, however, are viviparous, giving birth to live young. In terms of body shape, while both are flattened, skates often have a more rounded, triangular, or heart-shaped disc, sometimes with an extended, pointed snout, whereas rays are more commonly diamond-shaped.
Life Cycle and Behavior
Skates are marine carnivores found across various ocean environments. They inhabit temperate and cold waters, from shallow coastal regions to depths exceeding 2,700 meters (8,900 feet). Their diet primarily consists of small invertebrates and fish that live on or near the seabed. Skates utilize their grinding plates in their mouths to feed on prey such as shrimp, crabs, oysters, clams, and various small fish.
After internal fertilization, female skates lay leathery, oblong capsules, commonly known as “mermaid’s purses,” which often have distinctive horns at each corner. These egg cases are then anchored to the ocean floor or seaweed, providing a protected environment for the developing embryo. Depending on the species, the embryo can develop inside the egg case for several months, typically ranging from 9 to 12 months, before the young skate emerges fully formed. Each egg case usually contains a single embryo, although some species, like the big skate, can have up to seven embryos per case.