Phylum
Chordata
Characteristics of Chordates
Skeletal support
Becomes
brain and
spinal cord
Phylum Chordata: The Chordates
Urochordates: Tunicates, Salps
Cephalochordates: Lancelets
Vertebrata: Vertebrates
Sub-phylum Cephalochordata: Lancelets
Text 7.53
Live Amphioxus
Phylum Chordata, Sub-phylum Vertebrata: The Vertebrates
Fish Classes
Text 8.1
Class Agnatha: The Hagfishes
Text 8.2
Hagfish
https://www.youtube.com/watch?
v=tKTRv3hx1s0
Class Agnatha: Lampreys
Larval Lamprey
Lamprey Attached to a Trout
Lamprey
Mouth
https://www.youtube.com/watch?
v=AzZao6SVMyc
Class Chondrichthyes and Class Osteichthyes
Class Chondrichthyes
Rays
Ratfishes
Sharks
Common Characteristics:
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-cartilaginous skeleton
-teeth not fused to jaws and placed in rows
-presence of unsegmented epidermal fin rays
-single, ventral nostrils on each side of the head
-spiral valve intestine
-claspers on pelvic fins of males for internal fertilization
Class Chondrichthyes: Shark External Anatomy
Class Chondrichthyes: Ray External Anatomy
5-7 gill slits
• No operculum
• Most species (except bottom dwellers)
must swim constantly to breathe
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Placoid scales
• Also known as dermal
denticles
• Scales do not grow with
the shark – it grows
more scales to fill in the
gaps as it gets bigger
• Teeth are actually
modified scales
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Fins
• Caudal fin: heterocercal
!
!
!
!
• Thick, fleshy fins that don’t
move
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Large Oily Liver
• No swim bladder
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Spiracles
• Opening that supplies oxygen directly to
the eyes and brain
• Reduced or absent in fast swimming
species
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Diet
• As a whole, sharks and rays
eat everything
• Tiger sharks = “garbage
cans of the sea”
• Hammerheads = rays
• Bull sharks = other sharks
• Whale sharks = plankton
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Modes of Feeding
• Filter feeding – basking sharks, whale
sharks, manta rays
• Some are bottom feeders – rays, angel
shark
• Others swallow food whole
• In many: jaw extends from the rest of the
skull, lower jaw bites first, grasping and
upper teeth tear
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Senses
• Hearing: otolith in inner ear
• Use sound to locate food
• Ampullae of Lorenzini –receptors detect a weak electric field
• Lateral line: detect movement, vibrations
• Smell: paired nostrils; good sense of smell; can detect minute
amts of blood and other chemicals (1 part per billion)
• Vision: can see well in dim light
• Taste: have taste buds in mouth
Reproduction
• Some reach sexual maturity around 3-4
yrs of age – others not until 15+ yrs old
• Internal fertilization
• Claspers in males
• Some are oviparous (lay eggs)
• Some are viviparous (live birth)
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Humans and Sharks
• Numbers are decreasing due to overfishing
• Of the 350 species, 79 are in danger of
being depleted
• Vulnerable to overfishing – due to slow
growth, reproduction in later years,
females only have ~100 pups in a lifetime
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Humans and Sharks
• Numbers are decreasing due to
overfishing
• Of the 350 species, 79 are in
danger of being depleted
• Vulnerable to overfishing – due
to slow growth, reproduction
in later years, females only
have ~100 pups in a lifetime
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Shark Fin Soup
• 100 million
sharks killed
annually
• Increase in
demand (rise in
middle class
China)
• $100 bowl
• $500 per pound
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Fishing Tournaments
844 lb Mako – Destin 2007
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Shark Attacks
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Shark Attacks vs. Population in Florida
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Year 2000 Beach Injuries and Fatalities
Drowning and other beach-related fatalities: 1 in 2 million
!
Drowning fatalities: 1 in 3.5 million
!
Shark attacks 1 in 11.5 million
!
Shark attack fatalities 0 in 264.1 million !
Data from Lifeguards:
Estimated attendance 264,156,728
Unprovoked shark attack 23 Fatalities 0
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