Class Chondrichthyes
 Subclass Elasmobranchii
• Sharks
• Skates and Rays
 Subclass Holocephali
• Chimaeras (Ratfish)
 Traits
 Habitats
1
Buoyancy
 Huge oil-filled liver
• A shark that has an air weight of 1000 kg. weighs only 3.3kg in water
2
Buoyancy: Caudal Fins
 Homocercal
 Heterocercal
3
Respiration
 Chondrichthyes employ 3 different
methods of respiration
1. Buccal breathing (“Two pump” method)
2. Ram ventilation
3. Spiracles
4
External Covering
Scale Types
Placoid
Ganoid
Sharks, Skates
and Rays
Sturgeon &
Paddlefish
Cycloid
Ctenoid
Tarpon and
Ladyfish
5
Feeding
6
Feeding
 Digestion
• Spiral valve intestine
7
Movement
 Pelagic sharks
have rete
mirabile
8
Sensory Systems
 Hearing
 Olfaction
 Lateral Line
9
Sensory
Systems
 Visual systems are
well developed for
use during night
and day
• Tapetum lucidum =
increased vision at night
 Nictitating
membrane
10
Sensory Systems
 Ampullae of Lorenzini
11
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
13
Chondrichthyes
Reproduction
 Oviparity
 Viviparity
• Yolk-sac Viviparity
• Histotrophy (uterine viviparity)
• Cannibal viviparity
o Oophagy
o Adelphophagy
• Placental Viviparity
14
Oviparity - Egg Laying
 Oviparity
• Single (external)
• Multiple (retained)
15
Viviparity
 Yolk-sac Viviparity (old term “Ovoviviparity”)
• Eggs are produced and retained inside the mother
 Histotrophy (uterine viviparity)
• Mother secretes nutrient rich fluid which is taken up
through the skin of the embryo
16
Cannibal Viviparity
 Oophagy
• Young in each oviduct consume unfertilized
eggs
 Adelphophagy
• Young consume siblings
17
Placental Viviparity
 Nutrients are supplied to the embryo directly from the
mother via an umbilical cord
18
Chondrichthyes
Life History
 Strategy of Elasmobranchs
• K-selected species
• Precocial young
19
Subclass Holocephali
20