Stingrays

Graceful Predators

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The Institute for Marine Mammal Studies (IMMS) is a non-profit organization established in 1984 for the purpose of public education, conservation, and research of marine mam-mals and sea turtles in the wild and under hu-man care. Located in Gulfport, MS, IMMS has been an active participant in the National Stranding Network since its inception. IMMS is the premiere organization in the Mississippi-Louisiana-Alabama sub-region of the Gulf Coast with the capability and experience to care for sick and injured marine mammals and sea turtles. Additionally, IMMS promotes public awareness of marine conservation issues through its involvement in the community.

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Phone 228-896-9182 Fax: 228-896-9183 Email: contactus@imms.org

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Quick Facts Stingrays, skates, sharks, and chimeras are fish

that have skeletons comprised of cartilage.

It is believed that modern stingrays first appeared

approximately 60 million years ago.

The giant freshwater stingray can grow up to 16.5 feet long and weigh as much as 1,200 pounds.

Ancient Greek dentists used the venom from the stingray's spine as an anesthetic.

Stingrays have a lifespan of 15 to 25 years .

Stingray spines have been used by coastal tribes to create such weapons as spears and arrowheads.

Stingrays are counter-shaded (dark on top and light on bottom). This helps them hide from predators.

The tail of a stingray may be as much as 2.5 times as long as its body.

REMEMBER

References: www.elasmo-research.org/education/topics/lh_manta.htm

www.flmnh.ufl.edu

www.marinebiodiversity.ca

www.mmmedicaine.blogspot.com

As with other elasmobranchs, the liver of a

stingray is quiet large and oily. In some cases,

the liver can comprise as much as 25% of the

body weight. The rays need this oily liver to

aid in buoyancy because they lack swim blad-

ders found in most bony fish.

Other large organs in the rays are part of the

digestive tract. These organs include the

esophagus, the stomach, and the intestines. To

conserve space, rays have an intestine that is

coiled on the inside. This spiral valve—within

the intestines—increases the surface area in

which digestion takes place.

Other important organs include: the pancreas,

which aids in digestion by excreting enzymes

into the duodenum, a section of the intestines;

the spleen, which is an important component of

the immune system; the rectal gland, which

helps regulate the salt content in the blood-

stream; and the kidneys, which are involved in

the manufacture and movement of urine.

Stingrays reproduce through internal fertiliza-

tion. Most stingrays are ovoviviparous, mean-

ing the baby stingrays receive nutrients via a

yolk sac. This type of reproduction strategy is

sometimes referred to as “aplacental” and usu-

ally produces relatively large offspring. Most

ray species have litters of 5-15 pups. When a

male is courting a female, he follows her close-

ly and bites

in the area of

the pectoral

disc. Female

rays can store

sperm until

the optimum

conditions

for birth

arise.

Internal Anatomy Despite the fact that stingrays have camouflage

countershading and a sharp barb on their tails,

rays still encounter a large number of predators.

Hammerhead sharks in particular, are voracious

consumers of many ray species. Killer whales

also favor stingray flesh, as do many other spe-

cies of marine mammals. Other predators in-

clude: tiger sharks, bull sharks, and large carniv-

orous fish.

People are also a major predator of rays. Many

recreational fisherman seek stingrays for food

and recipes abound throughout the world. Some

commercial fisheries also actively seek ray

meat. The flesh of the stingray is often used as a

replace-

ment for

more valu-

able fish

and crusta-

ceans in

seafood

salads and

premixed

seafood

entrees.

This brochure is funded with qualified outer continental shelf oil

and gas revenues by the Coastal Impact Assistance Program,

United States Fish and Wildlife Service, U.S. Department of the

Interior through a grant award to the Mississippi Department of

Marine Resources.

Class: Chondrichthyes

Reproduction

Common Eagle Ray Myliobatis aquila http://mmmedicine.blogspot.com

Newborn Stingray dazeofadventure.com

Predators

Barbeque Stingray http://sparklette.net

Tiger Shark Consuming Ray http://thejohnharding.com

Prepared by Chris Breazeale, 2012

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Chondrichthyes

Subclass: Elasmobranchii

Order: Myliobatiformes

Scientific Classification

The Basics Stingrays are broad, flat, cartilaginous fish that

are closely related to sharks. There are about

200 species of sting rays that live throughout

the world in shallow, warm waters. Most are

euryhaline, meaning they can tolerate a wide

range of salinities. However some stingrays

live only in saltwater and others are strictly

fresh-water species. Stingrays can be catego-

rized into two groups: benthic and pelagic. Ben-

thic rays spend most of their time on or near the

bottom, while pelagic rays spend most of their

time swimming within the water column.

Stingrays are so named because most species

possess a large “stinger” or spine attached to

their tails. This spine, or barb is actually a

modified placoid scale. While not all stingrays

possess barbs, in some instances they can be

quite dangerous to humans.

Stingrays are fish with skeletons made entirely of

cartilage. As members of the class Chondrichthy-

es, stingrays are related to sharks, skates, and chi-

meras. Unlike bony fish, stingrays do not have a

gill covering. Instead, water flows over their gills

through gill slits. When stingrays are on the ocean

floor, they use small structures to “bring water in”

for distribution over the gills. Called spiracles,

these small openings allow the stingrays to

breathe while buried in the sand or when in some

feeding frenzies.

The bodies of stingrays are usually dorso-ventrally

depressed or “flattened” from top to bottom and

are covered with tiny placoid scales known as der-

mal denticles. Known as shagreen, the skin is

used to make leather goods and high-end com-

modities. Shagreen

was once highly

sought for its sandpa-

per-like qualities.

Items made from sha-

green have been found

in tombs of ancient

Egyptian pharaohs.

Stingrays have large pectoral fins that not only

give the ray its unique appearance, but also aid

in locomotion. Benthic rays tend to “ripple”

their fins to swim above the seafloor, while

pelagic rays “flap” their pectoral fins and ap-

pear to “fly” through the water.

Benthic rays also tend to differ from pelagic

rays in the way in which they are shaped. Ben-

thic rays usually have a rounded or diamond-

shaped body with barbs that are located near

the middle of the tail. Pelagic rays have a “bat-

like” appearance and have barbs that are locat-

ed nearer the pelvic/pectoral fins.

The spotted eagle

ray pictured above is

an example of a pe-

lagic ray.

Stingray teeth are modified placoid scales,

and like the dermal denticles, are less pro-

nounced in rays

than in most

shark species.

Most ray species

are opportunistic

feeders, devour-

ing prey items

whenever possi-

ble. Some rays,

like the manta ray, howev-

er, filter-feed on tiny

planktonic crustaceans and fish with the aid

of transverse gill plates called gill bars. The

cephalic (head) lobes give the manta ray its

distinct look while helping to channel water

into the mouth. Manta rays also differ from

most other rays in the fact they do not pos-

sess a stinging barb.

Stingrays have highly advanced organs

around their mouths called Ampullae of Lor-

inzini. These tiny openings can sense the

smallest electrical

currents which al-

lows the ray to de-

tect prey that is hid-

ing within the sub-

strate. Many rays

are equipped with

crusher plates that

allow them to crush

prey like crabs and

shrimp.

Common Stingray Jaws www.thefossilforum.com

Ampullae of Lorinzini http://earthguide.ucsd.edu

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www.flmnh.ufl.edu

Stingray Range http://images.nationalgeographic.com

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Ian Scott/iStockphoto

Manta Ray Feeding http://www.lesargonauts.com

Products made from stingray skin.

http://www.gypsyleather.com.au

Anatomy