Sharks, Skates, Rays and
Chimeras
Class Chondrichthyes
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Class Chondrichthyes
 Subclass Elasmobranchii
• Sharks
• Skates and Rays
 Subclass Holocephali
• Chimaeras (Ratfish)
 Traits
 Habitats
Class Chondrichthyes
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Adaptations
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Buoyancy
Respiration
External covering
Feeding
Movement
Sensory systems
Class Chondrichthyes
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Buoyancy
 Huge oil-filled liver
• A shark that has an air weight of 1,000 kg. weighs only 3.3kg in water
 Lift created by a heterocercal tail
Class Chondrichthyes
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Caudal Fin Types
 Homocercal
Class Chondrichthyes
 Heterocercal
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Respiration
 Chondrichthyes employ 3 different
methods of respiration
• “Two pump” method
 Ram ventilation
• Spiracles
Class Chondrichthyes
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External Covering
 All Chondrichthyes
have placoid scales in
one form or another
 Placoid scale
modifications
• Spine of stingray, dorsal
spine of dogfish,
defensive spines in the
skate, and teeth
Class Chondrichthyes
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Scale Types
Placoid:Sharks,
Skates and Rays
Cycloid: Tarpon
and Ladyfish
Class Chondrichthyes
Ganoid:
Sturgeon &
Paddlefish
Ctenoid
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Feeding
 Digestion
• Spiral valve
Class Chondrichthyes
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Movement
 Pelagic sharks
have rete
mirabile
Class Chondrichthyes
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Sensory Systems
 Elasmobranchs a have well-developed
sensory system which acts in concert to
locate prey and find their way around the
environment
• Some species can detect a drop of blood as
dilute as 1 part per billion
• Also, very good at following an odor trail
Class Chondrichthyes
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Sensory Systems
 Hearing
 Olfaction
 Lateral line
Class Chondrichthyes
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Sensory Systems
 Visual systems are
well developed for
use during night
and day
• Tapetum lucidum =
increased vision at night
 Nictitating
membrane
Class Chondrichthyes
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Sensory Systems
 Ampullae of Lorenzini
Class Chondrichthyes
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Chondrichthyes
Reproduction
 Most species have
extended gestation
periods in egg cases or
in the body cavities of
females
• Young traits
•Internal fertilization,
through the use of
claspers on the male
Class Chondrichthyes
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Chondrichthyes
Reproduction
 Oviparity
 Viviparity
•
•
•
•
Yolk-sac Viviparity
Uterine Viviparity
Cannibal Viviparity
Placental Viviparity
Class Chondrichthyes
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Oviparity - Egg Laying
 Oviparity
Class Chondrichthyes
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Viviparity
 Yolk-sac Viviparity (Ovoviviparity)
• Eggs are produced and retained inside the mother
• Shell disappears and young are retained until fully
developed
 Uterine Viviparity
• Mother secretes nutrient rich fluid which is taken up
through the skin of the embryo
Class Chondrichthyes
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Cannibal Viviparity
 Young in each
oviduct consume
unfertilized eggs
or other siblings
Class Chondrichthyes
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Placental Viviparity
 Nutrients are supplied to the embryo directly from the
mother via a umbilical cord
Class Chondrichthyes
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Chondrichthyes Life
History
 Strategy of Elasmobranchs
• Produce precocial young with high survival
rates
• Slow growing, long lived, and reach sexual
maturity at a late age
• This reproductive strategy is why
elasmobranchs can not sustain an intensive
fishery
Class Chondrichthyes
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Class Chondrichthyes
 Subclass Holocephali
• Possess cartilaginous
skeleton, intromittent
organs, spiral valve
intestine, and oil
filled liver
• As a group found
mostly between 802,600 meters,
feeding on hard
shelled invertebrates
Class Chondrichthyes
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