Internal Anatomy
Predators
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 bladders found in most bony fish.
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 species of marine mammals. Other predators include: tiger sharks, bull sharks, and large carnivorous 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 bloodstream; and the kidneys, which are involved in
the manufacture and movement of urine.
Reproduction
Stingrays reproduce through internal fertilization. Most stingrays are ovoviviparous, meaning the baby stingrays receive nutrients via a
yolk sac. This type of reproduction strategy is
sometimes referred to as “aplacental” and usually produces relatively large offspring. Most
ray species have litters of 5-15 pups. When a
male is courting a female, he follows her closely and bites
in the area of
the pectoral
disc. Female
rays can store
sperm until
the optimum
conditions
for birth
arise.
Newborn Stingray
dazeofadventure.com
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
replacement for
more valuable fish
and crustaceans in
seafood
salads and
premixed
seafood
entrees.
Barbeque Stingray http://sparklette.net
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.
Stingrays
Class: Chondrichthyes
Graceful Predators
REMEMBER
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 mammals and sea turtles in the wild and under human 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 MississippiLouisiana-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.
Common Eagle Ray Myliobatis aquila
http://mmmedicine.blogspot.com
Prepared by Chris Breazeale, 2012
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.
Tiger Shark Consuming Ray http://thejohnharding.com
References:
www.elasmo-research.org/education/topics/lh_manta.htm
www.flmnh.ufl.edu
www.marinebiodiversity.ca
www.mmmedicaine.blogspot.com
Institute for Marine Mammal Studies
P.O. Box 207, Gulfport, MS 39502
Phone 228-896-9182 Fax: 228-896-9183
Email: [email protected]
Website: www.imms.org
www.imms.org
Anatomy
Scientific Classification
Subphylum: Vertebrata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Myliobatiformes
Stingray Range http://images.nationalgeographic.com
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 categorized into two groups: benthic and pelagic. Benthic 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.
www.flmnh.ufl.edu
Stingray teeth are modified placoid scales,
and like the dermal denticles, are less pronounced in rays
than in most
shark species.
Most ray species
are opportunistic
feeders, devouring prey items
whenever possible. Some rays,
Stingray Jaws
like the manta ray, howev- Common
www.thefossilforum.com
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 possess a stinging barb.
Benthic rays also tend to differ from pelagic
rays in the way in which they are shaped. Benthic rays usually have a rounded or diamondshaped body with barbs that are located near
the middle of the tail. Pelagic rays have a “batlike” appearance and have barbs that are located nearer the pelvic/pectoral fins.
Manta Ray Feeding
The bodies of stingrays are usually dorso-ventrally
depressed or “flattened” from top to bottom and
are covered with tiny placoid scales known as dermal denticles. Known as shagreen, the skin is
used to make leather goods and high-end commodities. Shagreen
was once highly
sought for its sandpaper-like qualities.
Items made from shagreen have been found
in tombs of ancient
Products made from stingray skin.
Egyptian pharaohs.
http://www.gypsyleather.com.au
Ian Scott/iStockphoto
Stingray Barbs
oceanicshark.com.au
Phylum: Chordata
Stingrays are fish with skeletons made entirely of
cartilage. As members of the class Chondrichthyes, stingrays are related to sharks, skates, and chimeras. 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.
Giant Freshwater Stingray
www.extremescience.com/zeb-hogan.htm
Kingdom: Animalia
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 appear to “fly” through the water.
The spotted eagle
ray pictured above is
an example of a pelagic ray.
http://www.lesargonauts.com
Stingrays have highly advanced organs
around their mouths called Ampullae of Lorinzini. These tiny openings can sense the
smallest electrical
currents which allows the ray to detect prey that is hiding within the substrate. Many rays
are equipped with
crusher plates that
allow them to crush
Ampullae of Lorinzini
prey like crabs and
http://earthguide.ucsd.edu
shrimp.