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Marine Fishes
Part 1: Jawless & Cartilaginous Fishes
Vertebrates
• What defines a vertebrate?
– Backbone or spine
– Spinal cord
Jawless Fishes
• Most primitive
• Feed by suction
– round, muscular mouth
– Rows of teeth
• Elongated, cylindrical
body (like snake)
• No paired fins or scales
Lampreys
Hagfishes
• aka: slime eels
• No eyes
• Feed on dead or dying
fishes
• Can bore into prey and
eat from the inside out
• Pours slime out of
mucus sacs
– Can fill a 2 gallon bucket
instantly!
Hagfish
• Deep sea environment (1000
ft)
• Been around 300 million
years
• No eyes—virtually blind
• Highly acute sense of smell
and touch
• Smooth body helps it move
around inside dead animal
• Eat prey from the inside out
• Slime
– used as defense mechanism
– Protein explodes when in water
Hagfish Sliming Video - YouTube
Lampreys
• Primarily freshwater
• Breed in rivers and
lakes, move to sea as
adults
• Attach to fishes and
suck blood
Cartilaginous Fishes
• Sharks, rays, skates, and
ratfishes
• Skeleton of cartilage
– Lighter, more flexy than
bone
• Paired lateral fins for
swimming
Tiger Shark
Cartilaginous Fishes
• Movable jaws and teeth
• Mouth is ventral
– Underneath the head
Cartilaginous Fish
• Placoid Scales
– Rough, sandpaper like
– Pointed tip that points
backward
• produces a covering
that offers low
resistance and turbidity
• copied in the body suits
of Olympic swimmers.
The Perfect Predator
https://www.youtube.com/watch?v=Ssnjcz
QVLcY
The Perfect Predator: Body Shape
• Torpedo shape
– Body tapers at each end
• Well developed,
powerful caudal fin
• Arching the body
laterally into a shallow
curve
– Tremendous speed, low
energy useage
Mako Shark
The Perfect Predator: Coloration
• Dark on dorsal (top)
side
• Light on ventral
(bottom) side
• Why?
• White blends with light,
dark blends with
bottom
The Great White Shark
The Perfect Predator: Teeth
• Up to hundreds of teeth
in jaw at one time
• Embedded in flesh
– Not attached to jaw
• Multiple rows
• Serrated
• Replaced when lost –
for entire life!
The Perfect Predator: Eyes
• Extremely sensitive
– Able to magnify amount
of light
• Rolls eyes backwards
when attacking
– Exposes tough, fibrous
coat
The Perfect Predator: Nostrils
• ONLY used for smell
• Skin flaps
– Inflowing/outflowing
current
– Water passes over lamellae
• Lamellae
– Covered with millions of
sensory cells
– Single drop of blood in an
Olympic size pool
• Smell is directional
– Can tell where it’s coming
from
The Perfect Predator: Ampullae of
Lorenzini
• Thousands of small
capsules filled with jelly
• Picks up vibrations in
water of prey
• Detects electrical fields of
moving animals
• Detects magnetic field of
earth
– Used in migration
• More detail
Other Sharks: Whale Shark
• Largest shark (and fish) in ocean
– 65ft, 10+ tons
• Filter feeders
–
–
–
–
Fish eggs
Plankton
Krill
Small fish and squid
• Process over 6000 gallons of water/hr
Other Sharks: Hammerhead
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Sensory mechanisms all along flattened scull
Head acts as airplane wing
Can detect a billionth of a volt
Excellent 3-D eyesight
Excellent navigation
Importance of sharks
• Meat
– Nutritional, boneless,
mild-flavoring
• Eyes
– Corneas used as
substitutions for human
corneas
• Skin
– Used in research and
engineering of ships,
aircraft, pipelines and
swimming suits
Importance of sharks
• Liver
– Contain high amounts of
vitamin A (helps us see)
– Squaline
• Skin rejuvenator
• Cartilage
– Cancer research
• Ecosystem
– Apex predators
– Control disease
– Quick article
As Sharks Vanish, Chaotic New
Order Emerges
• What are some impacts that
have resulted in the
overfishing in sharks on the
east coast of the US?
• In your own words, what is
an “apex predator?”
• What is an example of a
“trophic cascade?”
• What is shark “finning?”
What are some problems
with it?
“This is how we do it in Oklahoma,
boy.”
Sharks are in great decline
• Overfishing
• K-selected species
– Low fecundity
• Do not produce many young
– Reproduce every two years
– Slow growth
– Late age of maturation
• Great White: 9 years; Sandbar: 25 years
• Cartilage:
– It cures cancer! NO IT DOESN’T! No
evidence!
– $100 million-a-year industry
Sharks are in great decline
• Bycatch
– Occurs in several
fisheries: tuna longline,
shrimp trawl, and
swordfish
– Millions of sharks a year
• Finning
– Removing the fins and
discarding the carcass
– This makes me sick to
my stomach…
Shark Finning
https://www.youtube.com/watch?v=mO7hv
OtYnck
Shark Fin Soup
Don’t be a “shark” hugger…Or you
may end up like this guy
How to Hug a Shark
https://www.youtube.com/watch?v=UtQAfR
rD8oc
=
WARNING: Don’t try this at home
Rays
Characteristics
• Adapted to living on
bottom of ocean
• Flattened bodies
• Gill slits (5 pairs) on
underside of body
• Feed on clams, crabs,
small fishes
Stingrays
• Lie camouflaged in
sand
• Finds food by smell,
touch and electrical
senses
• Up to 6 ft across
• Spine found at base
of tale laced with
poison
– Use in defense only
http://video.nationalgeographic.com/video/
stingray
A closer look at the tail
• This is a bull ray
– Same type of ray that
killed Steve Irwin
Manta Rays
• Largest of all rays
• Up to 22 feet across (average size is 12 ft)
Electric Ray
• Organs on side of head
that produce electricity
• Shocks up to 200 volts
– Used to stun prey
• Used by Romans to cure
treat headaches and
other ailments
• Confrontational if
harassed.
– Swim directly up to diver
Skates vs. Rays
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Rays live bearing (viviporous)
Skates are egg bearing (oviporous)
Rays have longer, skinnier tale with spine
Skates have fleshier tale, no spine
Rays have plate like teeth
Skates have small teeth
Which is which?