Skates are cartilaginous fish (elasmobranchs) related to sharks and rays. True skates (family Rajidae) do not possess the venomous, barbed spine characteristic of stingrays. Instead of a retractable stinger designed for venom delivery, skates rely on a different set of fixed, bony structures for protection. The absence of a venom gland and a serrated spine means skates are harmless to humans in the context of a painful, toxin-delivering wound.
Anatomy of the Skate Tail Thorns and Denticles
Skates feature various non-venomous, bony structures along their bodies that serve as a passive form of defense. These structures are modified placoid scales, the same tiny, tooth-like structures (dermal denticles) that give a shark’s skin its sandpaper-like texture. In skates, these scales are significantly enlarged and hardened into sharp projections.
These prominent structures are commonly referred to as thorns, prickles, or bucklers, depending on their size and location. Thorns often run in one or more longitudinal rows along the midline of the back and continue down the length of the tail. For example, the thorny skate (Amblyraja radiata) is named for the scattered denticles across its body and tail.
Unlike the stingray’s barb, which is a single, detachable weapon, a skate’s thorns are fixed and non-venomous. These projections deter predators, making the skate difficult to swallow or bite. Mature male skates also develop specialized patches of sharp, hooked thorns on their pectoral fins, known as alar thorns, which are used to anchor onto the female during mating.
Skates Versus Rays Key Differences
The confusion between skates and stingrays arises because both belong to the superorder Batoidea, a group of flattened, bottom-dwelling fish. They are classified into different orders, with skates belonging to Rajiformes and stingrays to Myliobatiformes. The most immediate difference is found in their tails: rays have slender, whip-like tails that often bear one or more sharp, venomous, serrated barbs.
Skates possess thick, fleshy tails that are devoid of any stinging spine. Another major distinction lies in their reproductive strategy: skates are oviparous, laying eggs encased in tough, leathery capsules often called “mermaid’s purses,” anchored to the seafloor.
Rays are viviparous, giving birth to live young after the embryos develop internally. Physical appearance also differs slightly; skates tend to have a more triangular or heart-shaped disc with a prominent dorsal fin located near the tip of their tail. Rays are typically more diamond-shaped, with the dorsal fin being reduced or entirely absent.
How Skates Defend Themselves
Since skates lack an active, offensive weapon like a venomous barb, their defense strategy is largely passive and behavioral. The primary defense is camouflage, as their flattened bodies and coloration allow them to bury themselves partially in the sandy or muddy bottom. When disturbed or threatened, their first reaction is often to remain motionless or quickly swim away.
The dense covering of dermal denticles and sharp thorns provides a substantial physical barrier against potential predators like sharks or larger fish. Some species, such as the thorny skate, can adopt a specific defensive posture by curling their pectoral fins and tail toward their ventral surface. This action exposes the maximum surface area of their heavily thorn-covered back to the threat, sometimes described as a “hedgehog” defense.
Skates also possess electric organs located in the tail muscle, a feature they share with electric rays, but the function is different. While electric rays use strong discharges for stunning prey or defense, the discharge produced by skates is weak. This low-voltage electricity is primarily used for social communication, such as reproductive signaling or territorial displays, rather than as a weapon.