Stinging spines vs. thorns, viviparous vs. oviparous—there are more differences between stingrays and skates than meets the eye.
Stinging Spines vs. Thorny Projections
If you take a look at a stingray's tail, you'll find their namesake stinging spines, or barbs, which they use as protection. These sharp, serrated spines deliver venom into predators—or into the feet of humans that accidentally step on a buried stingray, which can be extremely painful, but rarely fatal. Stingrays typically aren't aggressive but will protect themselves when threatened by raising their tails up, piercing the skin of their predators and injecting the venom.
Instead of stinging spines, skates' tails are lined with blunt, thorny projections, which also line skates' backs. These "thorns" aren't venomous like a stingray's spines, but they're also used for protection. A would-be predator, like a shark or grouper, that spots a skate may think twice about biting down on these thorn-like adornments.
The reproductive strategies of these two elasmobranchs are vastly different. Stingrays are viviparous, which means they give birth to fully formed young. Skates, however, are oviparous, which means they lay eggs.
If you've ever come across a rectangular, black, leathery pouch with horns extending from each corner while strolling the beach, you've found a skate egg case. These egg cases are sometimes referred to as mermaid's purses.
Another clue that can help distinguish these two elasmobranchs is size. It's not a hard-and-fast rule, but generally, stingrays are larger than skates.
Stingray's mouths are typically lined with flat, plate-like teeth that are used for crushing hard-shelled prey such as oysters and clams. Skates, on the other hand, have small, pointed teeth, which come in handy for capturing small fish, crustaceans and other prey.
When it comes to their classification within the animal kingdom, both stingrays and skates belong to the class Chondrichthyes—but then they diverge. Stingrays are in the order Myliobatiformes; skates are in the order Rajiformes.
There are exceptions to the general rule of long-and-thin tails for stingrays and short-and-thick tails for skates. For example, typical freshwater stingrays have relatively short, stout tails that are similar to a skate's tail, and the butterfly ray—a species of marine stingray—has a thin, but exceptionally short, tail.
And although thorn-like spikes are typically a telltale sign of skates, the roughtail stingray also sports bony "thorns" on its disc and tail.
Four species of stingrays and two species of skates can be found throughout the National Aquarium.