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Class Chondrichthyes 1 Sharks, Skates, Rays and Chimeras.

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Presentation on theme: "Class Chondrichthyes 1 Sharks, Skates, Rays and Chimeras."— Presentation transcript:

1 Class Chondrichthyes 1 Sharks, Skates, Rays and Chimeras

2 Class Chondrichthyes 2  Subclass Elasmobranchii Sharks Skates and Rays  Subclass Holocephali Chimaeras (Ratfish)  Traits  Habitats

3 Class Chondrichthyes 3 Adaptations  Buoyancy  Respiration  External covering  Feeding  Movement  Sensory systems

4 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

5 Class Chondrichthyes 5 Caudal Fin Types  Homocercal  Heterocercal

6 Class Chondrichthyes 6 Respiration  Chondrichthyes employ 3 different methods of respiration “Two pump” method  Ram ventilation Spiracles

7 Class Chondrichthyes 7

8 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

9 Class Chondrichthyes 9 Scale Types Placoid:Sharks, Skates and Rays Cycloid: Tarpon and Ladyfish Ganoid: Sturgeon & Paddlefish Ctenoid

10 Class Chondrichthyes 10 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 oUsed for grabbing and tearing oCan exert biting pressures of 2,800 kg/cm 3 Teeth are constantly being shed and replaced oUp to 30,000 in a lifetime


12 Class Chondrichthyes 12 Feeding  Digestion Spiral valve

13 Class Chondrichthyes 13 Movement  Pelagic sharks have rete mirabile

14 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

15 Class Chondrichthyes 15 Sensory Systems  Hearing  Olfaction  Lateral line

16 Class Chondrichthyes 16 Sensory Systems  Visual systems are well developed for use during night and day Tapetum lucidum = increased vision at night  Nictitating membrane

17 Class Chondrichthyes 17 Sensory Systems  Ampullae of Lorenzini


19 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

20 Class Chondrichthyes 20 Chondrichthyes Reproduction  Oviparity  Viviparity Yolk-sac Viviparity Uterine Viviparity Cannibal Viviparity Placental Viviparity

21 Class Chondrichthyes 21 Oviparity - Egg Laying  Oviparity

22 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

23 Class Chondrichthyes 23 Cannibal Viviparity  Young in each oviduct consume unfertilized eggs or other siblings

24 Class Chondrichthyes 24 Placental Viviparity  Nutrients are supplied to the embryo directly from the mother via a umbilical cord


26 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

27 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

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