Class Chondrichthyes 1

Sharks, Skates, Rays and Chimeras

Class Chondrichthyes 2

Class Chondrichthyes

Subclass Elasmobranchii• Sharks• Skates and Rays

Subclass Holocephali• Chimaeras (Ratfish)

Traits

Habitats

Class Chondrichthyes 3

Adaptations

Buoyancy Respiration External covering Feeding Movement Sensory systems

Class Chondrichthyes 4

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 5

Caudal Fin Types

Homocercal Heterocercal

Class Chondrichthyes 6

Respiration

Chondrichthyes employ 3 different methods of respiration• “Two pump” method

Ram ventilation• Spiracles

Class Chondrichthyes 7

Class Chondrichthyes 8

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 9

Scale Types

Placoid:Sharks, Skates and Rays

Cycloid: Tarpon and Ladyfish

Ganoid: Sturgeon & Paddlefish

Ctenoid

Class Chondrichthyes 12

Feeding

Digestion• Spiral valve

Class Chondrichthyes 13

Movement

Pelagic sharks have

rete mirabile

Class Chondrichthyes 14

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 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 19

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 a umbilical cord

Class Chondrichthyes 26

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 27

Class Chondrichthyes

Subclass Holocephali• Possess cartilaginous

skeleton, intromittent organs, spiral valve intestine, and oil filled liver

• As a group found mostly between 80-2,600 meters, feeding on hard shelled invertebrates