internal anatomy predators quick facts stingrays · the giant freshwater stingray can grow up to...
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Stingrays
Graceful Predators
www.imms.org
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.
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
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
Sti
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ray B
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.au
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