Bellwork: 02/20/2013 – Don’t start water changes yet 1)What is the defining characteristic of Chondrichthyes? 2)What are the two subclasses & give examples.

Bellwork: 02/20/2013 – Don’t start water changes yet

1) What is the defining characteristic of Chondrichthyes?

2) What are the two subclasses & give examples of each:

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Bellwork: 02/20/2013 - Continued

3) What is the name of the body form of sharks?

4) When did the radiation of chondrichthyes begin? What is the earliest period that scientists have found scales of chondrichthyes?

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Bellwork: 02/20/2013

Change the water on your tank.

Please scrub the glass & check the filters.

Class Chondrichthyes 3

Bellwork: 02/22/2013

Collect the following data: Salt Water Tanks Only:- Phosphate

Nitrate - Calcium Nitrite - Water Hardness Ammonia pH Temperature

Make sure to clean out any excess Make sure to clean out any excess food food from your filter and gravel/sand. from your filter and gravel/sand. Scrub offScrub off the inside of the glass & clean the the inside of the glass & clean the outside outside with Windex once you are finished. with Windex once you are finished.

Class Chondrichthyes 5

Sharks, Skates, Rays and Chimeras

Class Chondrichthyes 6

Class Chondrichthyes

Subclass Elasmobranchii• Sharks• Skates and Rays

Subclass Holocephali• Chimaeras (Ratfish)

Traits

Habitats

Bellwork:

1) List 3 differences between skates & rays:

2) Which organ is responsible for the buoyancy of many chondrichthyes?

3) List & describe respiration methods in chondrichthyes:

Class Chondrichthyes 7

Class Chondrichthyes 8

Class Chondrichthyes - Rays Subclass

Elasmobranchii• Thin, flexible, and barbed

tails• Can be extremely large

(25 feet across, weighing several tons)

• Serrated spines that are very difficult to remove from victim

• Spines are covered with a thin skin that contains painful toxins once ruptured

• Predominantly live-bearers

Class Chondrichthyes 9

Class Chondrichthyes - Skates

Subclass Elasmobranchii• Fleshy, heavy tails• Relatively small (1 to

5 feet)• Elongated nose• Often found in North

America• Large thorns for

defense, but not poisonous

• Lay eggs (mermaid’s purse)

Class Chondrichthyes 10

Class Chondrichthyes - Chimeras

Subclass Holocephali• Possess cartilaginous

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

• Single gill slit, no scales• Only have 6 permanent

teeth for grinding • As a group found

mostly between 80-2,600 meters, feeding on hard shelled invertebrates

Class Chondrichthyes 11

Chondrichthyes Life History

Strategy of Sharks & Rays•Produce precocial (well developed at birth) young with high survival rates

•Slow growing, long lived, and reach sexual maturity at a late age (13 to 19 years)

Class Chondrichthyes 12

Adaptations

Buoyancy Respiration External covering Feeding Movement Sensory systems

Class Chondrichthyes 13

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 14

Caudal Fin Types

Homocercal – two symmetrical lobes

Class Chondrichthyes 15

Caudal Fin Types

Heterocercal – much larger dorsal lobe

Class Chondrichthyes 16

Respiration

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

Ram ventilation• Spiracles

Class Chondrichthyes 17

Class Chondrichthyes 18

Respiration

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

Ram ventilation – species swims with mouth open

• Spiracles

Class Chondrichthyes 19

Respiration

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

Ram ventilation – species swims with mouth open

• Spiracles – small holes behind each eye that opens to the mouth in

Class Chondrichthyes 20

Respiration• Spiracles – small holes behind each eye

that opens to the mouth in.• This allows water to be drawn in from

above the organism

Spiracle

Class Chondrichthyes 21

Class Chondrichthyes 22

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 23

External Covering

Sting Ray Barb:

Class Chondrichthyes 24

External Covering

Dogfish Spine

Class Chondrichthyes 27

Feeding

Digestion• Spiral valve

Class Chondrichthyes 28

Circulatory

Pelagic sharks have rete mirabile (“wonderful net”)

Blood flows both ways in capillaries.

Arteries & veins are very close to each other

Class Chondrichthyes 29

Circulatory This lowers blood pH

allowing oxygen to unbind from hemoglobin & increase the overall oxygen saturation in the blood.

Allows thermoregulation, faster ATP breakdown, and ultimately faster swimming

Class Chondrichthyes 30

Sensory Systems

Sharks 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 31

Sensory Systems

Hearing Olfaction Lateral line

Class Chondrichthyes 32

Sensory Systems

Visual systems are well developed for use during night and day• Tapetum lucidum =

increased vision at night

Nictitating membrane

Class Chondrichthyes 33

Sensory Systems

Visual systems are well developed for use during night and day• Tapetum lucidum =

increased vision at night

Nictitating membrane

Class Chondrichthyes 34

Sensory Systems

Nictitating membrane – transparent 3rd eyelid

Sensory Systems

Sensory Systems

Sensory Systems

Sensory Systems

Sensory Systems

Sensory Systems

Class Chondrichthyes 41

Sensory Systems Ampullae of Lorenzini – electroreceptors (sense biological

electric fields) Tonic Immobility Tonic Immobility #2

Class Chondrichthyes 43

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 44

Chondrichthyes Reproduction

Oviparity – lays eggs (little or no embryonic development within the mother)

Viviparity – internal development• Yolk-sac Viviparity• Uterine Viviparity• Cannibal Viviparity• Placental Viviparity

Class Chondrichthyes 45

Oviparity - Egg Laying

Oviparity

Class Chondrichthyes 46

Oviparity - Egg Laying

Oviparity

Class Chondrichthyes 47

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 48

Cannibal Viviparity

Young in each oviduct consume unfertilized eggs or other siblings

Class Chondrichthyes 49

Placental Viviparity

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

In groups of two/three: Angel Shark River Stingray Wobbegong Shark Blacktip Reef Shark American Round

Bull Shark Stingray Goblin Shark Electric Ray Great White Shark Bottlenose Skate Hammerhead Shark Manta Ray Mako Shark Whip-tail sting Ray Nurse Shark Ghost Shark/elephant shark

Whale Shark Ratfish (not rattail) Tiger Shark Giant Stingray

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