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Chondrichthyes
Cartilaginous Fish
Characteristics
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Endoskeleton entirely cartilaginous
Fusiform Body
Mouth Ventral
Skin with placoid scales
2 chambered heart
Separate exposed gill slits
No operculum
Heterocercal tail
Internal reproduction (claspers & cloaca)
Fusiform body
• Torpedo shape
• Sharks have
countershading
(Dark on top & light
on the bottom)
Placoid Scales
• These scales point
towards the tail
and helps to reduce
friction from
surrounding water
when the shark
swims
Shark Anatomy
Shark Anatomy
Shark Senses
smell
hearing
lateral line organ
vision
ampullae of Lorenzini
touch and taste
How a Shark Eats
Two chambered heart
Gill Slits
Lack operculum
Heterocercal vs Homocercal
• Sharks have
heterocercal caudal
fins with the
vertebrae
extending into the
superior region of
the caudal fin
Shark Reproduction
• Male claspers are
inserted into
female cloaca for
internal
fertilization
• Ovoviviparous 90%
• Viviparous (Great
whites)
• Oviparous
Female Reproductive Anatomy
Male Reproductive Anatomy
Chondrichthyes
Reproduction
• oviparous (laying eggs that hatch outside the
mother's body)
• ovoviviparous (brooding eggs that hatch within the
mother's body, and then releasing the young)
• viviparous (young develop within a uterus inside the
mother's body, and are nourished prior to birth via
a connection with the mother's bloodstream
(placenta).
Cat Shark Egg
Oviparous
Porbeagle embryo viviparous
Dogfish Shark embryos
Ovoviviparous
Characteristics con’t
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No swimbladder or lung
2 olfactory lobes
2 cerebral hemispheres
2 optic lobes
1 cerebellum
1 medulla oblongata
3 pairs of semicircular canals
Ampullary organs of Lorenzini
Swimbladder
• Sharks lack a
swimbladder
• Oil in the liver is
used to change
buoyancy
Tapetum lucidum
Reflects light in the eye
Lateral Line System
Whale Shark
Worlds largest fish
(46 ft long)
Not many fossils
• Guitarfish
(One of the few
chondricthyes fossils)
Elasmobranchii
• Includes the familiar sharks,
skates, and rays, as well as some
strange fossil relatives.
• Elasmobranchs have an upper jaw
that is not fused to the braincase
and separate slit-like gill openings.
Rays & Skates
Rays & Skates
• Rays and Skates, unlike sharks, are not fusiform,
but dorsoventrally flattened.
• Gill slits open on the ventral surface of the head
• Spiracles on the top of the head direct water
over the gills, to prevent sludge from clogging
these delicate structures
• They feed primarily on mollusks and crustaceans,
and so have teeth modified for crushing.
Skates vs Rays
• The major difference between skates
and rays is the way in which they
reproduce.
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• Rays are viviparous (live bearing)
• Skates are oviparous (egg laying),
releasing their eggs in rectangular cases
sometimes called "mermaid´s purses".
Mermaid purse
Bradyodonti
• Includes forms with an upper jaw fused
to the braincase and a flap of skin, the
operculum, covering the gill slits.
• The Bradyodonti includes the chimaeras
and ratfish, which are relatively rare,
deep-water, mollusc-eating forms.
Chimaera
Ratfish