Skates and stingrays are cartilaginous fish that inhabit diverse marine environments. Despite their flattened bodies and bottom-dwelling habits, they belong to distinct groups within the class Chondrichthyes, which also includes sharks. While they share some broad characteristics, several key differences set them apart.
Visible Body Features
Skates and stingrays exhibit distinguishable physical characteristics. Skates generally possess a more triangular or diamond-shaped body disc, often appearing thicker and fleshier. Their tails are typically robust and short, featuring two prominent dorsal fins located closer to the tail’s tip. Additionally, skates have pelvic fins that are divided into two distinct lobes.
In contrast, stingrays tend to have flatter, more rounded or disc-like bodies. Their tails are thin and whip-like, often lacking prominent dorsal fins or having them greatly reduced. Stingrays also differ in their pelvic fin structure, possessing only one lobe on each side. When moving, skates propel themselves by flapping their pectoral fins, while stingrays typically undulate their entire body disc to glide through the water.
Tail Structures and Defenses
A primary distinguishing feature between these two groups lies in their tail structures and associated defense mechanisms. Skates do not possess a venomous barb on their tails. Instead, their tails may be adorned with small, thorny projections or prickles, which offer a form of physical protection against predators but are not venomous.
Conversely, stingrays are well-known for the presence of one or more serrated, venomous barbs located on their whip-like tails. These barbs are primarily used for defense, deployed when the animal feels threatened. The venom can cause intense pain, swelling, muscle cramps, and sometimes tissue necrosis in humans. While rarely fatal, a stingray injury requires medical attention.
How They Reproduce
Skates are oviparous, meaning they reproduce by laying eggs. These eggs are encased in distinctive, leathery capsules commonly known as “mermaid’s purses.” These egg cases are often rectangular with horn-like projections at each corner and can sometimes be found washed ashore on beaches. The developing embryo inside the mermaid’s purse is nourished by a yolk sac, and the incubation period can range from several months to over a year, depending on the species. While most skate species lay egg cases containing a single embryo, some, like the big skate, can produce capsules with multiple embryos.
In contrast, stingrays are viviparous or ovoviviparous, meaning they give birth to live young. The embryos develop internally within the mother, receiving nourishment from a yolk sac and later from a specialized uterine fluid, often referred to as “uterine milk” or histotroph. Stingray pups are born as miniature, fully formed versions of the adults, often capable of independent swimming and survival shortly after birth. Gestation periods vary by species.