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Class Chondrichthyes

Subclass Elasmobranchii• Sharks

• Skates and Rays

Subclass Holocephali• Chimaeras (Ratfish)

Traits

Habitats

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Buoyancy

Huge oil-filled liver• A shark that has an air weight of 1000 kg. weighs only 3.3kg in water

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Buoyancy: Caudal Fins

Homocercal

Heterocercal

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Respiration

Chondrichthyes employ 3 different methods of respiration

1. Buccal breathing (“Two pump” method)

2. Ram ventilation

3. Spiracles

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External Covering

Scale Types

Cycloid

Tarpon and

Ladyfish

Ganoid

Sturgeon &

Paddlefish

Ctenoid

Placoid

Sharks, Skates

and Rays

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Feeding

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Feeding

Digestion

• Spiral valve intestine

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Movement

Pelagic sharks have rete

mirabile

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Sensory Systems

Hearing

Olfaction

Lateral Line

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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

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Sensory Systems

Ampullae of Lorenzini

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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

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Chondrichthyes

Reproduction

Oviparity

Viviparity

• Yolk-sac Viviparity

• Histotrophy (uterine viviparity)

• Cannibal viviparity

o Oophagy

o Adelphophagy

• Placental Viviparity

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Oviparity - Egg Laying

Oviparity

• Single (external)

• Multiple (retained)

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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

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Cannibal Viviparity

Oophagy

• Young in each oviduct consume unfertilized eggs

Adelphophagy

• Young consume siblings

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Placental Viviparity

Nutrients are supplied to the embryo directly from the mother via an umbilical cord

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Chondrichthyes

Life History

Strategy of Elasmobranchs

• K-selected species

• Precocial young

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Subclass Holocephali