319reptiles1-170305124727.pdfdsdsdsaddsa

study of reptiles

1. Reptiles

2. Reptiles
First truly terrestrial
vertebrates
~7000 species
worldwide
~300 species in U.S.
and Canada

3. Reptiles
Probably best
remembered for what
they once were,
rather than what they
are now
Mesozoic era - age of
reptiles
Dominant group for
>150 millions years

4. Reptiles
12 or so principal
groups of reptiles
evolved
Only 4 groups remain
today

5. Order Squamata
Snakes and lizards
>5800 species
Most successful
group

6. Order Crocodilia
Crocodiles, alligators,
caiman
~25 species
Have survived for 200
million years
Today: concerns that
humans may drive
them to extinction

7. Order Chelonia (Testudines)
Turtles
~330 species
Ancient group that
survived, remained
mostly unchanged
from early ancestors

8. Order Rhynchocephalia
Snout head or tuatara
Only 1 species
From New Zealand -
sole surviving species
of ancestral stock

9. Reptilian Characteristics
Tough, dry scaly skin
Protection against
desiccation, physical
injury
Thin epidermis shed
periodically
Much thicker dermis
with chromatophores

10. Reptilian Characteristics
Dermis converted into
snakeskin, alligator
leather for shoes,
purses, and so on
Scales of keratin
(epidermal)
Not homologous to
bony, dermal fish
scales

11. Reptilian Characteristics
Crocodilian scales
remain throughout life
Grow gradually to
replace wear

12. Reptilian Characteristics
In snakes and lizards,
new scales grow
beneath old
Old scales shed with
old skin

13. Reptilian Characteristics
Turtles add new
layers of keratin
under old layers of
the plate-like scutes
(modified scales)

14. Shedding
Snakes turn old skin
(scales, epidermis)
inside out when
shedding

15. Shedding
Lizards split skin and
leave it right side out,
or slough it off in
pieces

16. Amniotic Egg
Chorioallantoic
membrane

17. Amniotic Egg
Reptiles are able to
lay their eggs in
sheltered locations on
land
Young hatch as lung-
breathing juveniles,
not aquatic larvae

18. Amniotic Egg
Amniotic egg widened
division between
amphibians and
reptiles
Probably greatly
contributed to decline
of amphibians and
rise of reptiles

19. Reptile Jaws
Reptile jaws designed
for crushing prey
Fish, amphibian jaws
designed for quick
closure, but little force
after
Reptile jaw muscles
larger, longer,
arranged for better
mechanical
advantage

20. Reptile Copulatory Organ
Copulatory organ
permitting internal
fertilization
Internal fertilization
required for a shelled
egg
Copulatory organ
formed from an
evagination of cloaca

21. Reptile Circulation
More efficient
circulatory system,
higher blood pressure
All reptiles have at
least an incomplete
separation of the
ventricles
Flow patterns prevent
mixing

22. Reptile Circulation
Crocodilians have two
completely separated
ventricles
All reptiles have two
functionally separate
circulations

23. Reptile Lungs
Improved lungs
Depend almost
exclusively on lungs
for gas exchange
Supplemented by
pharyngeal
membrane respiration
in some aquatic
turtles

24. Reptile Lungs
Lungs have larger
respiratory surface
than in amphibians
Air sucked into lungs
rather then forced in
by mouth muscles
Negative pressure
Skin breathing
completely
abandoned

25. Reptile Kidney
Kidneys more
advanced
(metanephric)
Very efficient at
conserving water
Excretes uric acid
(rather than urea,
ammonia)
A semisolid paste

26. Better Body Support
Limbs better design for walking on land
More ventral, less lateral
Many dinosaurs walked on only hindlimbs

27. Nervous System
Much more advanced - relatively larger
cerebrum
CNS connections more advanced - permit
complex behaviors not found in amphibians

28. Nervous System
Sense organs generally well-developed
Hearing generally poorly developed in most

29. Order Chelonia
Turtles
Very ancient group
Little change in
morphology since
Triassic period

30. Order Chelonia
Body enclosed in
shell
Dorsal carapace
Ventral plastron

31. Order Chelonia
Thoracic vertebrae
and ribs built into
shell
Shell of two layers
Inner of bone
Outer of keratin
New keratin
deposited under old
as turtle grows, ages

32. Order Chelonia
Jaws lack teeth
Equipped with tough,
horny plates for
gripping, chewing
food

33. Order Chelonia
Respiration poses a
problem
Shell prevents
expansion of chest for
breathing
Adapted to use
certain abdominal,
pectoral muscles as a
“diaphragm”

34. Order Chelonia
Air drawn in by
contracting limb flank
muscles to make
body cavity larger
Exhalation also active
- shoulder muscles
contracted, viscera
compressed, air
forced out of lungs

35. Order Chelonia
Deformable plastron
in snappers allows
some elastic recovery
during exhalation
Compressive force of
water against body
also can force air out

36. Order Chelonia
Many water turtles
acquire enough O
2

when inactive by
pumping water in and
out of mouth
Pharyngeal breathing
Can stay submerged
for extended periods
Must lung breathe
more frequently when
active

37. Order Chelonia
Nervous system - tiny brain
Typical of most reptiles
Never exceeding 1% of body weight, but
cerebrum larger than in amphibians
Turtle can learn, as quickly as a rat, to run a
maze

38. Order Chelonia
Have both middle
& inner ear, but
sound perception
is poor
Turtles are virtually
mute
Tortoises may
grunt or roar

39. Order Chelonia
Poor hearing
compensated for
by:
Good sense of
smell
Acute vision
Color perception as
good as that of
humans

40. Order Chelonia
Mating & reproduction
Many varieties of
courtship
Males of aquatic
species may swim
around looking for
proper leg stripe
pattern
Pheromones also
Males use claws

41. Order Chelonia
Terrestrial species
may vocalize
Males may track
females
(pheromones) for
days

42. Order Chelonia
Males may mark
territory with fecal
pellets
Courtship involves
rubbing limbs against
scent glands
(underside of jaw)
and sniffing

43. Order Chelonia
Biting, ramming,
hooking are directed
at other males
Biting - head & limbs
Ramming - rearing
up, smacking shells
Hooking - bulldozing
under plastron to flip
or hurry

44. Order Chelonia
Turtles are
oviparous
Fertilization is
internal, and all
species bury eggs
in ground in nests
4 to >100 eggs

45. Order Chelonia
Exercise care in
constructing nest
Deposit eggs and
abandon them
Incubation 1-14
months
40-60 days most
typical

46. Order Chelonia
Movements to nesting
areas very faithful
Terrestrial species
use familiarity with
area, sun
Marine species use
variety of
mechanisms to
traverse large
distances

47. Order Chelonia
Earth’s magnetic field
Polarized light
Sun & stars
Low frequency
sounds
Green sea turtles find
Ascension Island (20 km)
in mid-Atlantic from
coastal Brazil - 2200 km

48. Order Chelonia
Size - marine turtles
largest
Buoyed by aquatic
environment
May reach 2 m in
length, 725 kg in
weight
Biggest species is
leatherback

49. Order Chelonia
Green sea turtle may
exceed 360 kg
Economically
valuable - heavily
exploited - rarely gets
to large size

50. Order Chelonia
Land tortoises
generally not as large
as aquatic forms
Some may weigh
several hundred kg
Giant tortoises of
Galapagos Islands
among world’s largest
terrestrial turtles

51. Order Chelonia
Lifespan - turtles are
most long-lived
vertebrates
Individuals of at least
5 species known to
live 100 years or
longer
Some believed to
have lived more than
150 years

52. Order Chelonia
Longevity attributed to
slow rate of
metabolism
Galapagos tortoise
top speed: 300 m/hr
Reports of box turtle
caught in U.S. with
“1850” carved into
plastron
Skepticism!

53. Order Chelonia
Protective shell
Head, appendages
can be drawn in for
protection
Box turtles
especially good
because of hinged
plastron

54. Order Chelonia
Shell not as
protective in many
species
Soft, leather-like in
softshell turtles

55. Order Chelonia
Shell too small for
protection in other
species, e.g.,
snappers
Other means of
defense - ferocious,
short-tempered
“Tigers of the pond”

56. Order Chelonia
Entirely carnivorous -
fish, frogs, ducks,
whatever they can
catch
Alligator snapper
hides on bottom and
waves worm-like
tongue to attract fish
Wholly aquatic - come
ashore only to lay
eggs

57. Turtle Conservation
Slow growth, long
time to maturity
predispose many
species to risk of
extinction
Changing conditions
may increase adult
mortality, juvenile
recruitment

58. Turtle Conservation
Problem severe for
large tortoises, sea
turtles
Largest, slowest-
growing
Human and animal
invasion of beaches,
isolated island
habitats

59. Turtle Conservation
Herbivores compete
with tortoises for
limited vegetation
Eggs, young fall prey
to dogs, cats, rats

60. Turtle Conservation
Protection of land
tortoises simpler than
protection of sea
turtles
Limited range (single
island) defines limits
where protection is
needed

61. Turtle Conservation
Sea turtles range over
international, national
borders
Limited number of
breeding sites
Problems with
exploitation -
controlled or outright
ban?

62. Turtle Conservation
Ocean plastics
pollution - bags look
like natural jellyfish
prey
Not enough known
about biology do
devise protective
management program
Tag a turtle? 2000 X

69. Order Squamata
“characterized by
scales”
Lizards, snakes,
worm lizards
Most recent products
of reptile evolution
Most successful -
95% of known living
species of reptiles

70. Order Squamata
Lizards began
diversifying at time
when dinosaurs were
near end of their
dominance
Were successful
because of adaptability
Adopt various body
forms, occupy various
habitats

71. Order Squamata
Snakes likely arose
from group of lizards
whose descendents
include monitor lizards,
but fossil record poor

72. Order Squamata
Legless character
apparently evolved as
adaptation to
burrowing lifestyle
Snakes since have
radiated into
terrestrial, aquatic,
arboreal niches

73. Order Squamata
Two adaptations
characterize snakes:
Extreme body
elongation -
displacement,
rearrangement of
organs
Highly mobile jaws -
swallow prey larger
than own diameter

74. Order Squamata
Two suborders:
Sauria - lizards
“lizard”
Serpentes - snakes
“to creep”

75. Lizards
Very diversified group
(3300 species)
Terrestrial, burrowing,
aquatic, arboreal,
aerial
Many familiar groups:

76. Lizards
Geckos
Mostly small,
nocturnal, with
adhesive toe pads
(walk anywhere)

77. Lizards
Iguanas
Often bright-colored
New World lizards
Marine iguana - only
marine lizard in world

78. Lizards
Skinks
Elongate bodies,
reduced limbs

79. Lizards
Chameleons
Arboreal
Tongue flicked to
greater distance than
body length
Prehensile tail
Zygodactylous feet

80. Lizards
Independently
moveable eyes
elevated on cones -
good eyesight -
gauge distance
accurately

81. Lizards
Lizard body form not
as distinctive as other
reptiles
Many functional,
behavioral
modifications
e.g., degenerate or
absent limbs - no
good in dense grass

82. Lizards
Differ from snakes:
Halves of lower jaw
firmly united at
mandibular
symphysis
Teeth, but not
developed into fangs

83. Lizards
Moveable eyelids
(snake eyes covered
with permanent,
transparent cap)
Keen daylight vision

84. Lizards
Size - 3 cm to 3 m
Hawaiian gecko
Komodo dragon
75 kg
Fossils: 5.5 m, >1000 kg

85. Lizards
80% of lizards are
<20 g in weight
Generally
insectivorous
(opportunistic),
although some
specialists
N. Amer. horned
lizards eat only ants

86. Lizards
Most large lizards are
herbivores
Trees in tropics,
ground vegetation on
oceanic islands,
seaweed in ocean

87. Lizards
Monitor lizards are
exception to
vegetarians
Food of vertebrates
(birds, mammals),
invertebrates
Komodo - ambush
predator on large
mammals (deer,
goats, water buffalo)

88. Lizards
Foraging strategies:
Sit and wait (insects
come to them)
Active foragers (move
to encounter prey)

89. Lizards
Foraging modes
alternate at
successive levels of
food chain
Moving insect -> sit-
and-wait lizard ->
active predator
Sitting insect -> active
lizard -> sit-and-wait
predator

90. Lizards
May use territorial
and courtship
behaviors
Male anoles have
gular fan (dewlap) for
conspicuous displays
Skin distended by
hyoid apparatus

91. Lizards
Behaviors include:
Extending,
contracting fan
Pushups
Bobbing head

92. Lizards
Territories defended
by males for access
to females (bite &
chase, but no fighting)
Females have non-
overlapping home
ranges for feeding
Male territory includes
several females -
mates with all

93. Lizards
Mate by pressing
cloacal regions
together
Males grip female’s
neck, shoulders
Males have paired
copulatory organs -
hemipenes - to aid
sperm transfer

94. Lizards
Range of reproductive
modes from oviparity
to viviparity
Skinks - eggs
retained in oviducts,
receive nutrients
across a “placenta”

95. Lizards
All-female
(parthenogenetic)
species occur in at
least 6 families
Especially common
among racerunners
(Teiidae)
Diploids and triploids
known

96. Lizards
High reproductive
potential - every
individual capable of
producing offspring
Can repopulate
habitat faster than
bisexual species after
flood, other disaster

97. Lizards
Parental care
Many lizards remain
with eggs or nest site
Little if any care given
after young hatch or
are born

98. Suborder Serpentes - Snakes
2300 species
10 cm long up to 10
m long
Highly specialized
body form

99. Suborder Serpentes - Snakes
Entirely limbless
Lack pectoral, pelvic
girdles (except
vestige of latter in
pythons, boas)
Short, wide vertebrae
for quick lateral
undulations
Ribs improve rigidity

100. Suborder Serpentes - Snakes
Rearranged internal
anatomy
Left lung reduced or
absent
Gall bladder posterior
to liver
Right kidney anterior
to left
Gonads similarly
displaced

101. Suborder Serpentes - Snakes
Little modification for
various lifestyles:
Elongate for arboreal
Shorten for burrowing
Broaden for
swallowing big prey
Compress laterally for
swimming

102. Snake Sense Organs
Snake, lizard eyes
different: focusing, retina
morphology
Re-evolved from
burrowing ancestors
Permanent transparent
covering - non-blinking
stare
Lack of eyeball mobility
Poor vision - except
binocular in arboreal
snakes

103. Snake Sense Organs
Hearing - no obvious
external ear
No obvious response
to aerial sounds
Not deaf - have
internal ears - hearing
similar to lizards
Sensitive to vibrations
carried in ground

104. Snake Sense Organs
Olfaction important,
but not in nostrils
Jacobson’s organs
(vomeronasal organs)
Tongue carries scent
particles to organ

105. Snake Feeding
Skull, jaws highly
specialized for feeding
Eat prey several times
their own diameter
Non-joined mandibles
Loose skull bones
Tracheal opening far
forward between
mandibles

106. Snake Feeding
Prey swallowed head
first
Pulled in by teeth,
jaws, alternating side-
to-side
Contractions of neck
muscles force prey
down digestive tract

107. Snake Feeding
Two ways to subdue
prey:
Constricting - grab
prey in mouth and
suffocate by looping
body coils and
tightening

108. Snake Feeding
Venom - toxic
concentrations in
saliva
Neurotoxic -
blindness, paralysis
Hemolytic - ruptures
blood vessels, cells

109. Snake Feeding
Poisonous snakes in 4
families
Viperidae - viper, pit
vipers (heat sensitive)
Elapidae - coral snakes
(inject venom by
chewing)
Hydrophiidae - sea
snakes
Colubridae - rear-fanged -
venom to calm, not kill

110. Snake Feeding
Sea snakes have
most deadly venom
King cobra most
dangerous, largest
(5.5 m) - kill 9,000
people per year

111. Snake Locomotion
4 basic types:
Lateral undulation - S-
shaped path,
pressure against
surface irregularities

112. Snake Locomotion
Concertina movement
- movement upward
or along narrow
passages
Extend forward while
bracing S-shaped
loops

113. Snake Locomotion
Rectilinear movement
- slow, straight-line
movement

114. Snake Locomotion
Sidewinding - sandy
surfaces, body thrown
forward in loops, body
at 60° angle to line of
travel, 1 or 2 parts of
body in contact with
ground at once

115. Snake Reproduction
Most oviparous - lay
eggs in protected areas
Most of remainder are
ovoviviparous
(including rattlesnakes)
Very few viviparous
Females store sperm
from single mating, can
lay several clutches
over long interval

116. Order Crocodilia
Unchanged for 160
million years
Crocodiles larger, more
dangerous than
alligators
Prey drowned, ripped
into pieces by rapid
rolling
No natural enemies

117. Order Crocodilia
Oviparous - lay eggs in
mass of vegetation
Guarded by mother
Incubation temperature
determines sex of
alligator hatchlings
Low - females
High - males
5:1 (M:F) in some
areas

118. Order Crocodilia
Vocalizations by
hatchlings cause
mother to open next,
allow hatchlings to
escape
Some adults carry
young to water

119. Order Crocodilia
Mothers may guard
young in pools for
period of time to
protect them from
predators (fish,
mammals)

120. Order Sphenodonta
Tuatara - single
species in New
Zealand
Lizard-like, <66 cm
Lives in burrows
Slow-growing, long-
lived (77 years)

121. Order Sphenodonta
Living fossil - primitive
features identical to
fossilized forms
Primitive skull
structure
Well-developed
parietal eye with
retina, lens on top of
head (non-functional)