Transcript Sharks: Class Chondrichthyes

JAWS
• Teeth are modified scales
• Bottom jaw is like a fork
•
•
for grabbing and holding
prey
Top jaw is like a knife
with serrated edges to
cut through prey
Bite strength: 132 lbs.
between jaws = 22
tons/in2 at tips of teeth!
BODY
• Fusiform body
• Usually
countershaded
FINS
• Dorsal: stabilization
• Pectorals: steering
• Pelvic: stabilization
• Anal: stabilization
• Caudal: steering,
power, propulsion
CAUDAL FINS
Homocercal: top and
bottom lobes are equal
in length (GWS).
Heterocercal: top lobe is
longer than bottom lobe.
GILLS
• Most sharks have 5-7
pairs
• 6 and 7-gill sharks
probably represent
closer link to ancient
sharks
SCALES
• Placoid scales
• Dermal denticles
(skin teeth)
EXTRAS
• Spiracles: respiratory
•
•
structures present in
certain chondrichthyes
located just behind the
eyes. Water intake
valves.
Spiral Valve: In
stomach; increases
surface area for
absorption.
Squaline Oil: In liver;
increases buoyancy.
MORE EXTRAS
•
•
•
Opportunistic feeder:
Feeds when the
opportunity arises.
Obligate swimmer:
Must swim in order to
respire.
Tonic immobility:
Process by which
shark becomes
“paralyzed” by turning
it over on it’s back (It
appears to go to
sleep). This is a
temporary state!
SENSES
(in the order that they detect prey)
1. Hearing: sound
travels faster in
water, attracted to
low frequency
sounds emitted by
old, injured and /or
dying fish
2. Smell: Blood trail
(chum) stimulates
sense of smell
3. Lateral line: feel
vibrations from
wounded prey
SENSES
4. Vision: can spot prey
from 30 yards nictitating membrane
protects eyes.
5. Electroreception: (from
Ampullae of Lorenzini)
Jelly-filled sacs that
detect electrical fields
given off by all living
things, open wounds,
etc.
--Can detect up to one
millionth of a volt
6. Taste: upon contact
with prey
REPRODUCTION
Oviparous: Young hatch from egg
laid outside the mother. Cat
shark, Horn shark, Swell shark
Viviparous: live born sharks. Each
fertilized egg develops inside a
separate compartment in the mother’s
oviduct. Pup is feed via a placenta.
Lemon, Blue, Bull, Hammerhead
REPRODUCTION
Ovoviviparous: embryo
develops in a large yolky
egg kept inside the
female’s oviduct. Embryos
hatch while still inside the
mother then develop more
before being born.
--Sand Tiger, Thresher display
interuterine cannibalism:
where first pup to hatch in
each uterus will eat its
siblings.
Claspers: Two fingerlike
projections at the base of
the pelvic fins in MALE
sharks, (skates and rays).
4 Most Dangerous Sharks
Oceanic Whitetip
Great White
Bull
Tiger
SHARK ATTACKS
• Most shark attacks occur on
sunny days in near shore
waters 20C or warmer.
• Great White sharks prefer
colder waters.
• Most common body parts
attacked are the calves and
knees.
• Typically sharks will show an
Agnostic Display before they
attack: back is arched, pectoral
fins are pointed down, and
shark swims erratically.
WILL YOU BE ATTACKED?
• You have a better
•
•
chance of being killed
by a pig, bee, snake,
elephant, plane or car
crash.
You have a better
chance of winning the
lottery.
You have a better
chance of getting
struck by lightning
twice in the same
spot.
THE HARD TRUTH
• Fisherman kill
•
•
between 30-100
million sharks / year.
Sharks kill between
10-15 humans/year.
That means that for
every single human
killed, there are 10
million sharks killed!
RAYS
• Identified by the
•
•
presence of a barbed
stinger on their tail.
Swimmers can do the
“Stingray Shuffle” to
avoid getting stung.
If a person gets stung,
immerse the body part in
hot water to denature
(break down) the proteinbased venom.
Ray Migration
Gulf of Mexico
SKATES
• Skates have a pointed
•
“nose”, spots and
thorns or spikes on
their bodies, but no
stinger.
Egg cases are called
“Mermaid’s Purses”
and are commonly
found washed up on
beaches.
CHIMAERAS
• Often called Ratfish or Rabbitfish.
• Have a venomous spine at the front of the first
•
dorsal fin.
Males have a 5th clasper on their head.