Transcript RAYS AND SKATES UPCLOSE! FLORIDA PROGRAM FOR SHARK RESEARCH Florida Museum of Natural History.

RAYS AND SKATES
UPCLOSE!
FLORIDA PROGRAM FOR SHARK RESEARCH
Florida Museum of Natural History
Rays and Skates Upclose!
•Ray and Skate Basics
•Ray and Skate Biology
•Ray and Skate Conservation
•Ray and Skate Research
RAY AND SKATE
BASICS
What is a ray?
© George Ryschkewitsch
• Rays are dorsoventrally flattened fish that are closely related to sharks.
• All are considered to be within a closely related group of fish called
elasmobranchs.
• Rays belong to three scientific orders - Pristiformes, Myliobatiformes,
and Torpediniformes
What is a skate?
© George Burgess
• Skates are dorsoventrally flattened fish that are closely related to
sharks.
• All are considered to be within a closely related group of fish called
elasmobranchs.
• Skates are classified in the order Rajiformes.
Are all rays considered stingrays?
• Stingrays are a type of ray, however not all rays are stingrays as this
group also includes electric rays, butterfly rays, round rays, manta rays,
guitarfish, and sawfish.
How many species of rays and skates
are there?
• There are approximately
500 different species of rays
and skates that are divided
into 18 families when
scientifically classified.
What are the differences between
rays and skates?
• The major difference between rays and skates is in their reproductive
strategies.
• Rays are live bearing (viviparous) while skates are egg laying
(oviparous), releasing their eggs in hard rectangular cases sometimes
called "mermaid´s purses".
How long have rays and skates
existed?
U.S. National Park Service
• The fossil record of rays and skates dates back to the Lower Jurassic
(150 million years ago).
Do rays and skates have bones?
© Cathleen Bester
• Rays and skates have no bones, but instead have skeletons made of
cartilage as do sharks.
• Cartilage is tough and fibrous but not as hard as true bones.
How do rays and skates swim?
© Doug Perrine
• These unique animals swim through the water by gracefully
undulating the modified pectoral fins, appearing to fly through the
water.
• They sometimes make spectacular leaps from the surface of the water.
Are stingrays dangerous to people?
© Cathleen Bester
• Stingrays have venomous spines along or near the base of the tail.
The muscular whip-like tail can be lashed about quickly in defense.
• Occasionally beach-goers will accidentally step on stingrays that are
partially buried in the sand near the beach resulting in a painful, serious
wound in the foot.
Where do rays and skates live?
• Rays and skates live in oceans throughout the world.
• Most rays and skates are benthic while some are pelagic.
• Some rays live in freshwater habitats
Can rays and skates live in
freshwater?
• In Florida, the Atlantic stingray
(Dasyatis sabina) is known to live in
freshwater along the St. Johns River
waterway as well as inland
freshwater lakes.
• These populations of the Atlantic
stingray are unique in that they spend
their entire lifecycle in freshwater.
© Doug Perrine
RAY AND SKATE
BIOLOGY
© Tobey Curtis
What are some adaptions of rays and
skates?
• The dorso-ventrally flattened
bodies allow rays and skates to
glide closely over the bottom
sediments in search of prey.
• Their eyes and spiracles are
positioned on the top of the
head, allowing them to take in
water for respiration while
partially buried in the sand.
© George Burgess
• The mouth is located on the
underside of the animal as an
adaptation for feeding on
benthic invertebrates and fishes.
What does ray and skate skin feel
like?
• The skin feels exactly like
sandpaper because it is made up of
tiny teeth-like structures called dermal
denticles.
• Skate skin may also possess thorns
which help to defend them from
predators.
Do rays and skates have good vision?
© Doug Perrine
• The eyes of rays and skates are located dorsally, on the upper surface
of the animal, while the mouth is located on the underside.
• It is believed that vision may play only a secondary role in prey
location and feeding behaviors.
How do rays and skates detect prey?
© George Burgess
Ampullae of Lorenzini on a sandbar shark
• Rays and skates use the senses of smell (chemoreception), vision,
hearing, the lateral line system, and electroreception (ampullae of
Lorenzini) for capturing prey.
• The lateral line system, which most fish possess, allows them to detect
waves of pressure or mechanical disturbances in the water.
What do rays and skates eat?
•The majority of rays and skates feed on bottom dwelling (benthic)
animals including shrimps, crabs, oysters, clams and other invertebrates.
• Some rays such as the manta and devil rays are filter feeders relying on
plankton as their food source.
Do rays and skates have any
predators?
• Sharks, in particular
hammerheads, often have
spines in their digestive
tracts and imbedded in
their jaws from feeding
on stingrays.
© George Burgess
How can you distinguish a male from
a female ray or skate?
• Male rays and skates (as well as
sharks) have claspers while females
do not.
• Claspers are modifications of the
pelvic fins and located on the inner
margin of the pelvic fins. They are
used to transfer sperm to the female
during mating.
Do rays and skates give live birth or
lay eggs?
• Rays give live birth while skates
lay eggs in egg cases (as pictured
above) referred to as "mermaid's
purses".
© George Burgess
Do rays and skates take care of their
young?
• Neither rays or skates exhibit
parental care other than
moving to a protective area to
lay eggs or give birth.
© James Sulikowski
RAY AND SKATE
RESEARCH
© Christina Conrath
What are some current ray and
skate-related research projects?
© Christina Conrath
• Tagging and tracking rays in some of the waterways along the coast of
Florida. The data from this project will assist in the identification of daily
and seasonal movements of rays.
• The reproductive biology of skates and the feeding ecology of rays and
skates in the Pacific Ocean.
• The age and growth of a skate species that has declined more than 95%
due to take as bycatch in the New England groundfisheries.
RAY AND SKATE
CONSERVATION
© Doug Perrine
Are rays and skates threatened or
endangered?
• Unfortunately, there are many species of rays and skates that are
considered threatened and endangered.
• The IUCN Red List includes 547 species of elasmobranchs of which at
least 20% are in danger of extinction.
Further Information:
http://www.flmnh.ufl.edu/fish/Education/education.htm
FLORIDA PROGRAM FOR SHARK RESEARCH
Florida Museum of Natural History