Chondrichthyes
An Overview
Chondrichthyes
• Are jawed cartilaginous fish composed of
sharks, skates, and rays
• They have a skeleton made up of cartilage
and do not have any bones
• They have existed on earth for over 400
million years
• They are mostly ectothermic – have body
temperatures similar to the temperature of
the water around them
Chondricthyes Organisms
Sharks and Ratfishes
• Shark (top) Ratfish (bottom)
Skates and Rays
• Skate( top) Ray (bottom)
SHARKS, SKATES, AND RAYS
• What do you know about them?
• How have they been able to survive on Earth
for so very long when so many other
organisms have perished?
• Are they more beneficial or more harmful to
humans?
Sharks
• These fishes have teeth-like scales called
denticles.
• Their mouth is usually located ventrally and they
were the first fish to have paired fins (pectoral &
pelvic fins) for more efficient swimming.
• They have 5 to 7 gill slits per side and no swim
bladder.
• The largest shark, the whale shark is a plankton
feeder.
Shark Adaptations for Survival
http://www.pbs.org/wnet/nature/lessons/sy
mbiotic-strategies/video-segments/1496/
http://www.youtube.com/watch?v=nmvc35pnC
YE
Shark
Internal Anatomy
• No Bones
Shark
External Anatomy
Fusiform Body
Shape that reduces
frictional drag
How a Shark Swims
• http://www.youtube.com/watch?v=Itag3_mR
c4w
• How a shark maintains buoyancy
• http://dsc.discovery.com/videos/the-ultimateguide-to-sharks-how-sharks-swim.html
Denticles
Shark Senses
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Sound
Smell
Sight
Electromagnetic Fields
Touch
Shark Hearing
Sound Travels 5X faster in water than air and quite
far. Sharks have inner ears but no outer ears.
They are attracted most by low-pitched sounds.
Sharks cannot make any noises, they have no
vocal cords.
Bursts of sound, like that made by injured fish are
particularly attractive. This is also the sound made
by humans splashing in the water.
Shark Sense of Smell
• Will then help the shark to move closer to the prey.
• Through its nares (nostrils), sharks can detect one
part of blood in many millions of parts of water.
(One part per million is equivalent to you taking
one large mouthful of food compared to all the
large mouthfuls you will take in a lifetime).
• http://dsc.discovery.com/videos/ultimate-guidethe-sharks-shark-smell.html
Shark Breathe Through Openings
Called Nares (nostrils)
Sharks Sense of Sight
They can see extremely well in dim light. While
bony fishes cannot dilate their irises, sharks can to
allow more or less light to reach their retinas.
Some sharks have a third eyelid called the
“nictitating membrane” that can move to cover
the eye completely to protect it during feeding.
• http://dsc.discovery.com/videos/ultimateguide-the-sharks-vibrations-and-sharkvision.html
Sharks Senses
• http://www.youtube.com/watch?v=D78jCw7E
QYk
Sharks Eye and Eyelids
Sharks Sense of Electromagnetic
Fields
Produced by the prey can be detected by sharks.
The “Ampullae of Lorenzini”, electro-receptors,
located on the snout of the shark, allows them to
detect weak electrical currents produced by a
prey's gill movement.
Sharks detect weak electromagnetic
Fields using the Ampullae of Lorenzini
Shark Touch and Taste
• Sharks can feel touch with their skin
• Sharks can taste their prey with their tongue
Sharks Detect Vibrations and changes
in water pressure with their Lateral
line
How Sharks Use Their Senses
60 Minutes
Swimming with Sharks
• http://www.cbsnews.com/8301-504803_16257344500-10391709/anderson-cooperswimming-with-sharks/?tag=mncol;lst;1
Shark Mating
• Mating behaviour in sharks can be very
complex and evidence suggests that there is
some degree of mate selection within certain
species. Sexes often segregate, and only come
together to mate. Occasionally congregations
form in mating behavior. For instance, basking
sharks have been seen forming mating circles
like the one seen in this picture. The exact
purpose of this behavior is not known
however it is clear that it related to mating.
Shark Mating and Reproduction
Mating
• http://videos.howstuffworks.com/discovery/3
6705-ultimate-guide-to-sharks-shark-matingvideo.htm
• http://www.sharkinformation.org/video/mati
ng-sharks-shanghai-aquarium/JD1_hVJ4ZoM/
Reproduction
• http://dsc.discovery.com/videos/shark-weekshark-reproduction.html
Shark Birth and Maturation
• http://dsc.discovery.com/videos/ultimateguide-the-sharks-shark-birth-andmaturation.html
Female Shark
Female Shark
Male Shark
Male and Female Shark
SHARK REPRODUCTION
• Oviparous – lay eggs and spawn (ex. White
Spotted Bamboo Shark)
• Viviparous – give birth to live young who feed
from a placenta (ex. Lemon Shark)
• Ovoviviparous – eggs are fertilized and
develop with a yolk sac inside the mother (ex.
Grey Nurse Shark)
White Spotted Bamboo Shark
Lemon Shark
Grey Nurse Shark
Grey Nurse Mating
• http://news.nationalgeographic.com/news/20
06/02/0213_060213_shark_video.html
PARTHENOGENESIS IN SHARKS
• Give birth to young without mating. An egg
develops without fertilization by sperm. One
of the mother’s polar bodies fuses with an
ovum during meiosis. Was observed in a
Bonnethead shark in captivity.
http://www.youtube.com/watch?v=jzzg4YEpY28
SHARK INTELLIGENCE
• Are sharks intelligent?
• What would indicate that an organism has
intelligence?
• http://www.youtube.com/watch?v=zPlTKiSXc
G0&feature=list_related&playnext=1&list=SPA
15DA8E609E85873
• http://www.youtube.com/watch?v=vG4x7CrC
uJU&feature=relmfu
SHARK INTELLIGENCE
• EVIDENCE
– Expressing Curiosity – examining people and
objects for no apparent reason (ex. Divers, Square
Shapes) (Recognizing certain divers and boats)
– Recognizing the front from the back of a person or
object (ex. Circling round and spending more time
observing the front from the back)
• Almost always attack from back
• Gently mauling a diver without attacking
SOCIAL BEHAVIOR
• Sharks were thought to be asocial living their
lives alone with little interest in socializing
except for mating
• Thought to lack the cognitive ability for social
behavior
• NEW Evidence?
EVIDENCE OF SOCIAL BEHAVIOR
• GREAT WHITE sharks worked together pulling
a Pygmy right Whale out to sea so it could
float and be eaten more easily. Some swam
away without feeding
• Others were shown a square and a seal shape
and spent more time examining the square
shape
EVIDENCE OF SOCIAL BEHAVIOR
• Great Whites have been seen spending time
together in pairs of same and age peers (2
females show up together each year off San
Francisco’s coast
SOCIAL BEHAVIOR
• Communicate using body language
– Arched bodies and gaping mouths (go away)
– Individual timed turns between to sharks
– Maintaining individual space
– Tail slapping
– Breaching to attract a mate
Shark Self Defense and Shark
Attack
• How do sharks defend
themselves or avoid
predation?
SELF DEFENSE
a. The natural enemies of sharks include other
sharks, killer whales and the most dangerous
to sharks, by far, are humans
b. Gill nets kill sharks and mammals when the
intended catch is actually fish. Sharks can
drown if they do not have water running over
their gills.
Gill Net
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Gill Net
• Thresher Shark caught in gill net
Lemon Shark
Caught in Gill Net
Megaladon
• http://www.youtube.com/watch?v=5L_oXfUh
kTE&feature=related
SELF DEFENSE
• c. Sharks have a protective coloration to hide
them on the bottom or in reefs and exhibit
counter-shading to hid them while free
swimming in the open ocean.
• d. The bamboo shark can come out of the
water for hours to follow prey or avoid
predators.
Shark Attack
• http://www.youtube.com/watch?v=SlVjttMTAM&feature=relmfu
SHARK ATTACK
a. A shark may attack a rogue shark, or people
swimming who sound like an injured fish and may be
mistaken for natural prey.
b. Many attacks involve spear fishers: sharks are
attracted to fluttering movements of an injured fish
c. A shark bothered by a swimmer or diver may
attack.
d. 99% of the cases in which a rescuer goes to the
aid of a victim they are not attacked.
What sharks are deadliest or most
harmful to Humans? Why?
• 1. Bull Shark
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2. Great White
3. Tiger Shark
4. White Tip Oceanic Shark
5. Shortfin Mako Shark
6. Grey Reef Shark
7. Sand Tiger Shark
8. Hammerhead Shark
9. Blue Shark
10. Lemon Shark
What sharks are the most
beneficial to Humans? How?
• 1. All Apex Predator Sharks
• 2. Mako Sharks
• 3. Nurse Sharks
Spear Fishing
Spear Fishing
Spear Fishing
SHARK ATTACK
e. There is a statistical preference of sharks for
males over females among swimmers; 1
female is attacked for every 9 males. Less than
1/2% of attacks on scuba divers were on
women (1 out of 244) and she was spear
fishing. This may be a reaction to a territorial
intruder with movement of men more
threatening than women.
Shark Attack
Shark Attack
SHARK ATTACK
f. 80% of attacks involve 1 or 2 bites; no intent to kill?
Maybe a human doesn't react like other prey when
bitten and it looses interest. We certainly do not
taste like other prey.
g. When an attack does occur it is likely to be a single
bite and not an attempt to consume the human.
Death may occur due to blood loss. Humans do not
taste like other natural shark food and are not
desirable to a healthy shark.
SHARK ATTACK
h. Of the approximately 360 plus known
species of shark, of which about 250 species
are now alive, only about 25 have ever been
identified in a human attack for one reason or
another. The most dangerous are the white,
mako, tiger and bull sharks.
SHARK ATTACK
I. The majority of attacks have occurred in
temperate waters within 67m/200’ of shore
and in a depth of 1.5m/5’ of water.
To avoid an attack by a shark there
are a few things to know. DO NOT
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1. Dive or swim alone.
2. Dive or swim at night
3. Keep captured fish near you in the water.
4. Spear fish over a prolonged time in one area.
5. Enter the water if you have a cut.
6. Panic and splash at the surface if you see a shark.
7. DO get out of the water as fast and quietly as
possible.
What about skates and rays?
What would a shark or ray say
about humans if interviewed?
How to tell the difference
between a skate and a ray.
Location of Gill Slits on a Skate or
Ray
Reproduction in a Skate
Manta Ray