What is the difference between skates and rays?
13 August 1999
Skates and rays are similar species and are closely related to sharks. Collectively, they are known as batoids. Like sharks, their skeletons are made of cartilage instead of bones. Cartilaginous fish belong to the class of fishes known as Chondrichthyes.
Most rays are kite-shaped, with streamlined tails that may have one or more venomous barbs, sometimes called spines. In contrast, skate tails are fleshier and heavier and have small fins. In general, skates commonly found in North American waters have elongated noses.
Size is another way to differentiate rays from their skate cousins. Rays can grow to tremendous sizes. The manta ray (Manta birostris) can reach a width of 22 feet and weigh several tons. The five species of skates commonly found in North Carolina waters range in size from 16 inches to 5 feet in length.
Rays and skates use different mechanisms for defense. The venomous barb on the ray’s tail is an effective weapon against predators. The edges of the barb are serrated so that once the barb enters a victim it is very difficult to remove without causing more damage. A thin skin covers the entire barb. When the thin sheath is ruptured, venom is released. Skates do not have barbs, relying instead on large thorns on their backs and tails to deter predators.
Skates and rays also differ in the way they give birth. Skates lay eggs in leathery cases very similar to shark egg capsules. These cases sometimes wash up on beaches and are romantically nicknamed “mermaid purses.” Rays, on the other hand, give birth to live young.
Despite obvious distinctions, classifications of these unique animals are often subject to debate among researchers. It doesn’t help that sometimes “ray” is used as a catchall for both ray and skate species. However, according to the International Code of Zoological Nomenclature, the majority of rays belong to the scientific order Myliobatiformes – with one exception, the electric rays, which belong to the order Torpediniformes. Skates are members of a completely separate order known as Rajiformes.
In all, there are seven main families of rays in the order Myliobatiformes, including stingray, butterfly, devil, eagle, river, round and six-gill ray. Some of the individual species common off the North Carolina coast are the smooth butterfly (Gymnura micura), spotted eagle (Aetobatus narinari), cownose (Rhinoptera bonasus) and southern stingray (Dasyatis americana).
There is only one family of skates, the Rajidae. Skates common to North Carolina include the clearnose (Raja eglanteria), winter (Raja ocellata), little skate (Raja erinacea) and barndoor skate (Raja laevis).
According to the Diver’s Alert Network, most stingray injuries occur when an unseen stingray is stepped upon. The ray, in an effort to defend itself, flips up its tail in an attempt to inject its barb to dissuade or disable the intruder. If successful, the result is a serious puncture wound. In humans, stingray venom can cause the following reactions:
* Pain which may last several days
* Nausea and Vomiting
* Appetite Loss
* Muscular Cramps, Tremor and Paralysis
Because removal of a stingray barb can often make the wound worse, it is best to seek immediate medical attention. If you are injured by a stingray and cannot get immediate medical assistance:
* Irrigate the wound to remove surface venom.
* Carefully try to remove any portions of the barb and sheath that remain in the wound. It may be best to let a doctor attempt this.
* Immerse the area in hot water (113 F) for 30 to 90 minutes or until pain is relieved.
* Seek medical attention as soon as possible.
* Sharks and Their Relatives — Sea World
* The American Elasmobranch Society
* Rays: Wings in the Waters — National Aquarium