Sharks, Skates, Rays and
Chimeras
Class Chondrichthyes
1
Class Chondrichthyes
 Subclass Elasmobranchii
• Sharks
• Skates and Rays
 Subclass Holocephali
• Chimaeras (Ratfish)
 Traits
 Habitats
Class Chondrichthyes
2
Adaptations






Buoyancy
Respiration
External covering
Feeding
Movement
Sensory systems
Class Chondrichthyes
3
Buoyancy
 Huge oil-filled liver
• A shark that has an air weight of 1000 kg. weighs only 3.3kg in water
 Lift created by a heterocercal tail
Class Chondrichthyes
4
Caudal Fin Types
 Homocercal
Class Chondrichthyes
 Heterocercal
5
Respiration
 Chondrichthyes employ 3 different
methods of respiration
• “Two pump” method
 Ram ventilation
• Spiracles
Class Chondrichthyes
6
Class Chondrichthyes
7
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
8
Scale Types
Placoid
Ganoid
Sharks, Skates
and Rays
Sturgeon &
Paddlefish
Cycloid
Ctenoid
Tarpon and
Ladyfish
Class Chondrichthyes
9
Feeding
 Most are specialized predators and have
dentition that reflects their lifestyle
• Sharks that prey on fish and marine
mammals have triangular blade-like teeth
o Used for grabbing and tearing
o Can exert biting pressures of 2,800 kg/cm3
• Teeth are constantly being shed and replaced
o Up to 30,000 in a lifetime
Class Chondrichthyes
10
Feeding
 Digestion
• Spiral valve intestine
Class Chondrichthyes
12
Movement
 Pelagic sharks
have rete
mirabile
Class Chondrichthyes
13
Class Chondrichthyes
14
Sensory Systems
 Elasmobranchs have a 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 10 billion
• Also, very good at following an odor trail
Class Chondrichthyes
15
Sensory Systems
 Hearing
 Olfaction
 Lateral Line
Class Chondrichthyes
16
Sensory Systems
 Visual systems are
well developed for
use during night
and day
• Tapetum lucidum =
increased vision at night
 Nictitating
membrane
Class Chondrichthyes
17
Sensory Systems
 Ampullae of Lorenzini
Class Chondrichthyes
18
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
20
Chondrichthyes
Reproduction
 Oviparity
 Viviparity
•
•
•
•
Yolk-sac Viviparity
Uterine Viviparity
Cannibal Viviparity
Placental Viviparity
Class Chondrichthyes
21
Oviparity - Egg Laying
 Oviparity
Class Chondrichthyes
22
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
23
Cannibal Viviparity
 Young in each
oviduct consume
unfertilized eggs
or other siblings
Class Chondrichthyes
24
Placental Viviparity
 Nutrients are supplied to the embryo directly from the
mother via an umbilical cord
Class Chondrichthyes
25
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 cannot sustain an intensive
fishery
Class Chondrichthyes
27
Class Chondrichthyes
 Subclass Holocephali
• Possess cartilaginous
skeleton, male
intromittent organs,
spiral valve intestine,
and oil filled liver
• As a group found
mostly between 802600 meters, feeding
on hard shelled
invertebrates
Class Chondrichthyes
28