Class Chondrichthyes 1 Sharks, Skates, Rays and Chimeras.
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Transcript of Class Chondrichthyes 1 Sharks, Skates, Rays and Chimeras.
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