Bellwork: 02/12/2014 – Don’t
start water changes yet
1) What is the defining characteristic of
Chondrichthyes?
2) What are the two subclasses & give examples
of each:
1
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?
2
Bellwork: 02/12/2014
 Change the water on your tank.
 Please scrub the glass & check the filters.
 Clean of the glass lids as well
Class Chondrichthyes
3
Sharks, Skates, Rays and
Chimeras
Class Chondrichthyes
4
Class Chondrichthyes
 Subclass Elasmobranchii
• Sharks
• Skates and Rays
 Subclass Holocephali
• Chimaeras (Ratfish)
 Traits
 Habitats
Class Chondrichthyes
5
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
6
Class Chondrichthyes Rays
 Subclass Elasmobranchii
Class Chondrichthyes
• 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- 7
bearers
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
8
Class Chondrichthyes Chimeras
 Subclass Holocephali
Class Chondrichthyes
• 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 9
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
10
Adaptations






Buoyancy
Respiration
External covering
Feeding
Movement
Sensory systems
Class Chondrichthyes
11
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
12
Caudal Fin Types
 Homocercal – two symmetrical lobes
Class Chondrichthyes
13
Caudal Fin Types
 Heterocercal – much larger dorsal lobe
Class Chondrichthyes
14
Respiration
 Chondrichthyes employ 3 different
methods of respiration
• “Two pump” method
 Ram ventilation
• Spiracles
Class Chondrichthyes
15
Class Chondrichthyes
16
Respiration
 Chondrichthyes employ 3 different
methods of respiration
• “Two pump” method
 Ram ventilation – species swims with mouth
open
• Spiracles
Class Chondrichthyes
17
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
18
Respiration
• Spiracles – small holes behind each eye that
opens to the mouth.
• This allows water to be drawn in from above
the organism
Class Chondrichthyes
19
Spiracle
Class Chondrichthyes
20
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
21
External Covering
Sting Ray Barb:
Class Chondrichthyes
22
External Covering
Dogfish Spine
Class Chondrichthyes
23
Feeding
 Digestion
• Spiral valve
Class Chondrichthyes
26
Circulatory
 Pelagic sharks
have rete
mirabile
(“wonderful net”)
 Blood flows both
ways in
capillaries.
 Arteries & veins
are very close to
each other
Class Chondrichthyes
27
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
28
Circulatory
Class Chondrichthyes
29
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
30
Sensory Systems
 Hearing
 Olfaction
 Lateral line
Class Chondrichthyes
31
Sensory Systems
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
Class Chondrichthyes
35
Sensory Systems
Sensory Systems
Sensory Systems
Sensory Systems
Sensory Systems
Sensory Systems
Sensory Systems
 Ampullae of Lorenzini – electroreceptors (sense
biological electric fields)
 Tonic Immobility
 Tonic Immobility #2
Class Chondrichthyes
42
Ampullae of Lorenzini
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
45
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
46
Oviparity - Egg Laying
 Oviparity
Class Chondrichthyes
47
Oviparity - Egg Laying
 Oviparity
Class Chondrichthyes
48
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
49
Viviparity
 Yolk-sac Viviparity (Ovoviviparity)
Class Chondrichthyes
50
Cannibal Viviparity/oophagy
 Young in each
oviduct consume
unfertilized eggs
or other siblings
(Sand Tiger
Sharks)
Class Chondrichthyes
51
Cannibal Viviparity/oophagy
Class Chondrichthyes
52
Placental Viviparity
 Nutrients are supplied to the embryo directly from the
mother via a umbilical cord
Class Chondrichthyes
53
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
55