Chapter 20 Reptiles

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Chapter 20Reptiles

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Introduction

• Class Reptilia
• Order Testudines or Chelonia -----Turtles
• Order Rhynchocephalia------------Tuataras
• Order Squamata------------------snakes, lizards,
  worm lizards
• Order Crocodilia-------------------crocodiles,
  alligators, caimans, gavials.

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Evolutionary Perspective

• I. It is believed that the earliest members of
  the reptile family were the first to have
  amniotic eggs.
• A. Characteristics of amniotic eggs
• 1.Extraembronic membranes (protect the embryo
  from desiccation).
• 2. cushion the embryo
• 3. promote gas transfer
• 4. store waste materials
• 5. leathery or hard shells
• 6. albumen cushions the embryo and provides
  moisture and nutrients
• 7. yolk supplies food

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Amniotic Egg
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Basic Characteristics of the Reptile Group

• 1. They have a skull with 1 surface for movement
  with the first neck vertebra
• 2. respiration by lungs
• 3. kidneys
• 4. internal fertilization
• 5. amniotic eggs
• 6. dry skin with keratinized epidermal scales
• note there are 17 orders of reptiles, most
  extinct, 4 orders today.

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NO not a chicken
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Compare and Contrast
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Order Testudines (Chelonia)Turtles

• Roughly 225 species of turtles
• Characteristics
• 1.bony shell
• 2. limbs articulating internally to the ribs
• 3. keratinized beak rather than teeth
• 4. hinge that allows the shell to open and close
  (head and legs to come in and out)
• 5. 8 cervical vertebrae (which can curve into S
  shape which allows turtles head to be drawn in)

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Order Testudines (Chelonia)Turtles

• 6. long life spans
• (reach sexual maturity at 7-8 years, and live 14
  years or more, some on the Galapagos Islands may
  live in excess of 100 years)
• 7. oviparous (eggs are deposited outside the
  body)
• Females use hind limbs to excavate nests in the
  soil. They lay eggs there and cover with soil.
  Usually laid in clutches of 5-100 eggs.

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Order RhynchocephaliaLizardlike Reptiles

• Characteristics
• 1. two rows of teeth on the upper jaw, and a
  single row on the lower jaw
• gives them a bite that could decapitate a
  small bird
• 2. widely distributed in New Zealand
• 3. often fall prey to human influences and
  domestic animals
• 4. oviparous (lay eggs outside the body)
• 5. share underground burrows with seabirds
• 6. venture out of their burrows at dusk and dawn
  to feed on insects or occasionally small
  vertebrates.
• See picture on page 316, Figure 20.7

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Stopped here on feb 25
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Order Squamata

• Broken down into
• Suborder Sauria THE LIZARDS
• Suborder Serpentes- THE SNAKES
• Suborder Amphisbaenia- WORM LIZARDS

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Suborder Sauria THE LIZARDS

• Characteristics
• 1. 3,300 species
• 2. two pairs of legs
• 3. upper and lower jaws unite anteriorly
• 4. length varies from 1 centimeter to 3 meters
• 5. live on surface substrates
• 6. hide or live under rocks or logs
• 7. some burrow or stay in trees
• 8. deposit eggs under rocks or debris or in
  burrows
• 9. can be oviparous, ovoviviparous, viviparous
• Examples Geckos, Iguanas, Gila Monster the
  only venomous lizards known.

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Suborder Serpentes- The Snakes

• Characteristics
• 1. 2,300 species of snakes
• 2. 300 species are venomous
• 3. Worldwide about 30-40,000 people die from
  snake bites, most of these are in Southeast Asia
• 4. elongated
• 5. lack limbs
• 6. may have more than 200 vertebrae and pairs of
  ribs
• 7. upper jaws are movable, loosely connected to
  lower jaw
• 8. Narrowing of the body has resulted in loss of
  left lung, displacement of gallbladder, the right
  kidney, and often the gonads.
• 9. Most snakes are oviparous
• 10. However the New World boas, garter snakes
  give birth to live young.

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Suborder Amphisbaenia- Worm Lizards

• Characteristics
• 1. 135 species
• 2. specialized burrowers of soil in Africa
• 3. most are legless
• 4. skulls are wedge or shovel shaped
• 5. single median tooth in the upper jaw
• 6. skin has ring like folds
• 7. feed on worms and small insects
• 8. oviparous

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Order Crocodilia

• Characteristics
• 1. 21 species
• 2. triangular eye openings for the eye openings
• 3. laterally compressed teeth
• 4. elongated snout
• 5. nostrils are at the tip of the snout
• 6. muscular, elongated tail that is laterally
  compressed tail for swimming
• 7. food is swallowed whole
• 8. the stomach is like a gizard, they swallow
  rocks and other objects to be used in breaking
  apart food and digestion
• 9. oviparous, lay eggs outside body and build
  nests

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Alligator
70-80 white, pointed teeth of similar shape
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Alligator

• Length in wild
• 8-9" at birth
• typical old male 15', female about 10'
• largest recorded in Florida -- 17'5"
• Weight in wild
• varies among alligators and is not related to
  length
• largest males can weigh up to 1,000 pounds
• Body
• adults black
• young have vertical yellow bands until about 3-4
  years old (see photo below in "Young")
• Famous for the death roll. Grab the prey go down
  into the water and spin until the prey drowns.

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Crocodiles
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Crocodiles

• Size greatly varies between species, from the
  dwarf crocodile to the saltwater crocodile.
  Species of Palaeosuchus and Osteolaemus grow to
  an adult size of just 1 metre (3.3 ft) to
  1.5 metres (4.9 ft). Larger species can reach
  over 4.85 metres (15.9 ft) long and weigh well
  over 1,200 kilograms (2,600 lb). Crocodilians
  show pronounced sexual dimorphism with males
  growing much larger and more rapidly than females.

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Crocodiles

• Ambush Hunters Crocodiles are ambush hunters,
  waiting for fish or land animals to come close,
  then rushing out to attack. As cold-blooded
  predators, they can survive long periods without
  food, and rarely need to actively go hunting.
  Known for having lock jaw. Escape rarely happens.
• World's Largest Reptile The largest species of
  crocodile, also Earth's largest reptile, is the
  Saltwater Crocodile, found in northern Australia
  and throughout South-east Asia.

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Crocodile products

• Crocodile leather wallets from Bangkok Crocodile
  Farm
• Crocodile leather can be made into goods such as
  wallets, briefcases, purses, handbags, belts,
  hats, and shoes.
• Crocodile meat is consumed in some countries,
  such as Australia, Ethiopia, Thailand, South
  Africa and also Cuba (in pickled form) it can
  also be found in specialty restaurants in some
  parts of the United States. The meat is white and
  its nutritional composition compares favourably
  with that of other meats. It tends to have a
  slightly higher cholesterol level than other
  meats. Crocodile meat has a delicate flavour
  some describe it as a cross between chicken and
  crab. Cuts of meat include backstrap and tail
  fillet.

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Locomotion

• Unlike amphibians the reptile family can not
  breath through their skin. Their skin serves no
  respiratory function.
• Characteristics of Reptile Skin
• Dry
• Thick
• Keratinized (hardened scales)
• Snakes use their scales to provide contact with
  substrates (trees, grass, dirt) and create
  movement.

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Locomotion

• The periodic shedding of skin is called ecdysis.
  And happens periodically. It usually starts at
  the head and then moves down the body. Some shed
  complete skins and others flake off in pieces.
• When a snake is going through this it is called
  opec cycle. And the snake will have a blue hue to
  it.
• The epidermis is the outer layer and it has no
  blood vessels and very few chromatophors or color
  pigments.

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Locomotion

• Most Reptiles walk on legs, others slither on the
  ground.
• Reptiles have a lot of mobility in their neck
  region. The atlas and axis are the upper cervical
  vertebra in the neck.
• The ribs are closely associated with the leg or
  belly movements. Muscle concentration is high
  here.
• In order to escape predators some lizards can go
  through autotomy, loose their tail to get away
  and grow a new one.
• Prehistoric reptiles walked on their back two
  legs and this is called being bipedal.
• Most reptiles today walk on all four legs. Knee
  and elbow joints rotate posteriorly in most.

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Nutrition and Digestion

• Most Reptiles are Carnivores (eat meat)
• One exception are turtles who will eat just about
  anything.
• Some reptiles have a sticky tongue to help catch
  prey, and the length of the tongue can be longer
  than the body of the reptile.
• Jaws of reptiles are loosely attached and often
  can be unhinged to allow them to eat large prey.
  The upper jaw is called the maxillary and the
  lower the mandible. Fangs are usually associated
  with the maxillary bone.
• Inside the mouth of the snake they have a glottis
  which is a respiratory opening that allows them
  to breath while eating.

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Nutrition and Digestion

• Some fangs are always in a straight or vertical
  position. Others can be folded up and then
  unfolded when needed.
• Venom glands used to kill prey are actually
  modified sweat glands. That venom is moved
  through the fang into the prey.
• Most of these cocktails contain neurotoxins
  (attacking the preys nervous system) or
  Hemotoxins (which break up blood cells and cause
  the victim to suffocate to death from the lack of
  oxygen to the body cells.

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Body Temperature

• Reptiles are cold blooded.
• Reptiles and amphibians are very similar in this
  area.
• Reptiles have a higher blood pressure because
  blood must be pumped at high speeds to reach all
  parts of the body.
• Reptiles use their environment to help regulate
  their temperature.
• The lack of breathing is called apnea. Turtles
  can not breath when they go into their shells.

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Nervous and Sensory Functions of Reptiles

• The reptiles cerebral hemisphere (a large portion
  of the brain) is larger than that of the
  amphibian. The increased size is believed to be
  associated with the sense of smell capabilities
  of the reptile.
• Also the optic lobes (found in between the
  cerebrum and the cerebellum) and cerebellum
  (found behind the cerebrum) are enlarged. This
  helps with vision and greater coordination of
  muscle functions.

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Nervous and Sensory Functions of Reptiles
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Nervous and Sensory Functions of Reptiles

• Vision is the dominant sense in most reptiles.
• Some reptiles have an additional eye in the roof
  of the forebrain. Page 403. This is called a
  median (parietal) eye. It is covered with skin
  and is not known to be able to form any images.
  It does help with the detection of light and dark
  periods.
• Ears-
• Detect vibrations
• Lack a middle ear cavity, auditory tube, tympanic
  membrane.

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Nervous and Sensory Functions of Reptiles

• The jaw works with (articulates) with the stapes
  in the ear and receives Substrate vibrations
  (vibrations from physical objects, ground, etc).
• Snakes can also detect air vibrations.
• Taste
• Jacobsons organs (vomeronasal)- are pouhces that
  open through the palate of the reptile. Turtles
  do not have these. Baby crocodiles have this but
  adults do not. Snakes and lizards have these and
  they work with their forked tongues to sample
  chemicals in the air.

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Jacobsons Organs
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Nervous and Sensory Functions of Reptiles

• Pit organs
• Rattlesnakes and other vipers have these heat
  sensitive organs. They are located on each side
  fo the face between the eye and nostril.
• They are used to detect temperature. Mostly they
  are used to detect warm blooded prey at night.

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• Anatomy of a snake.
• 1 esophagus,
• 2 trachea,
• 3 tracheal lungs,
• 4 rudimentary left lung,
• 5 right lung,
• 6 heart,
• 7 liver,
• 8 stomach,
• 9 air sac,
• 10 gallbladder,
• 11 pancreas,
• 12 spleen,
• 13 intestine,
• 14 testicles,
• 15 kidneys.

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Reproduction

• Structures-
• Gonads are the male reproductive structures that
  are ducts designed to conduct sperm to the
  cloaca.
• Seminal receptacle- is a storage area in the
  female that allows the female to store sperm
  until they are used. This area will nourish the
  sperm. In some sperm is stored for 4-6 years
  before being used.

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Reproduction

• Copulation- is the scientific word for mating.
• Fertilization- is when a sperm and egg unite to
  form a zygote
• Courtship- any behavior that attracts a mate.
  They use body language, sound, color, sight,
  smell.
• Tactile stimulation- the use of tail waving to
  attract or acquire a mate.
• Sex pheromones- smells used to tell if the
  opposite sex is ready to mate.

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Reproduction

• Vocalizations- sounds used during mating season
  to attract a mate, or warn off predators.
• Nest- any area built by the reptile for the
  purpose of rearing young. Most reptile nests are
  on the ground and made of dirt and sticks.
• Parhenogenesis- is a form of asexual reproduction
  found in females, where growth and development of
  embryos occurs without fertilization by a male

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Reproduction

• Snake 2 - 3 months, live birth and eggs,
  internal fertilization
• Alligator-Offspring
• Alligator females will typically build a nest
  near water where she will deposit 30-50 eggs. She
  will bury the nest with vegetation and mud which
  raise 2-3 feet above ground level. She will guard
  the nest through the 60-day gestation period and
  aid the hatchlings with breaking out of the nest.
  Hatchlings will form social groups called "pods"
  and remain with the mother for up to a year after
  birth.

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Reproduction

• Crocodiles-
• This species digs hole nests up to 50cm deep in
  sandy banks, several metres from the water. These
  may be in close proximity to other nests. Timing
  of nesting behaviour varies with geographic
  location - it takes place during the dry season
  in the north, but at the start of the rainy
  season further south, usually from November
  through to the end of December. Females reach
  sexual maturity around 2.6 m, males at around 3.1
  m. Females lay around 40 to 60 eggs in the nest,
  although this number is quite variable between
  different populations. Females remain near the
  nest at all times.

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Reproduction

• Incubation time averages 80 to 90 days (ranges
  from 70 to 100 days), after which females open
  the nest and carry the juveniles to the water.
  Both males and females have been reported to
  assist hatching by gently cracking open eggs
  between their tongue and upper palate. Hatchlings
  remain close to the juveniles for up to two years
  after hatching, often forming a creche with other
  females. As with many crocodilians, older
  juveniles tend to stay away from older, more
  territorial animals.