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Ask the Aquarium: What is the Difference Between Skates and Rays?

13 August 1999

 

Rays and skates are similar species that 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 poisonous barbs or 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 tremendously large sizes. For example, the manta ray (Manta birostris) can reach a width of 22 feet, weighing 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 to defend themselves, too. The stinging spine on the ray’s tail is an effective weapon against predators. The edges of the spine are serrated so that once driven into a victim it is very difficult to remove without creating more damage. A thin skin covers the entire structure, and when ruptured, venom is released into the victim. Since skates do not have stinging spines, they rely on large thorns on their backs and tails to deter predators.

Skates and rays differ from each other in the way they give birth. All skates lay eggs, which are leathery cases very similar to shark egg capsules. These cases sometimes wash up on beaches and are called mermaid’s purses. Rays, on the other hand, give birth to live young.

 

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Graceful Gliders: The cownose ray is one of several species found off the North Carolina Coast.  The cownose is one of a few rays that will jump out of the water, landing with a loud "smack".   Researchers believe this behavior might be a territorial display.

 

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The Southern Stingray is one of the most common rays found along our shore.  This ray often lies buried in the sand so that only its eyes and spiracles (nostrils) are exposed.

 

 

   

Additional Resources

These differences determine how skates and rays are categorized and classified scientifically. Despite the obvious distinctions, classifications of these unique animals are often the subject of debate among researchers. It doesn’t help that sometimes "ray" is used as a catchall category that encompasses 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 completely separate order known as Rajiformes.

 

In all, there are seven main families of rays in the Order Myliobatiformes, including stingrays, butterfly rays, devil rays, eagle rays, river rays, round stingrays and six-gill rays. Some of the individual species common off the North Carolina coast are the smooth butterfly ray (Gymnura micura), the spotted eagle ray (Aetobatus narinari), the cownose ray (Rhinoptera bonasus) and the southern stingray (Dasyatis americana).

There is only one family of skates, the family Rajidae. Skates common to North Carolina include the clearnose skate (Raja eglanteria), the winter skate (Raja ocellata), the little skate (Raja erinacea), and the barndoor skate (Raja laevis).        

First Aid for Stingray Injuries    firstaid.jpg (3275 bytes)

 

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, injects its spine into the victim, causing a serious puncture wound.  A sheath covers the entire spine, and when ruptured, venom is released into the victim. Stingray venom can cause the following reactions:

  • Pain which may last several days
  • Swelling
  • Nausea and Vomiting
  • Diarrhea
  • Appetite Loss
  • Muscular Cramps, Tremor and Paralysis

Because removal of a stingray spine can often make the wound worse, it is best to seek immediate medical attention.

If you are stung by a stingray and cannot get immediate medical assistance:

  • Irrigate the wound to remove surface venom.
  • Carefully try to remove any portions of the spine 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.