Class: Amphibians (Chapter 40)

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• Class Amphibians (Chapter 40)
• The name amphibian means "double life
• For while adult amphibians usually live on land,
  their soft eggs must be laid in the water.

References Holt Biology text
resources http//z.about.com/d/animals/1/0/W/5/shu
tterstock_716539.jpg http//dnr.wi.gov/org/caer/ce
/eek/critter/amphibian/index.htm
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I. Amphibian evolution orders

• Preadaptations are adaptations in an ancestral
  group that allow a shift to new functions which
  are later favored by natural selection.
• Lobe-finned fishes preadaptations that allowed
  transition to life on land
• bone structure
• pouches in digestive tracts for gas exchange
• nostrils
• higher metabolism
• efficient hearts
• Lobbed finned fish were probably amphibian
  ancestors

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A. Evolution of Amphibians

• Amphibians and lobe-finned fishes share many
  anatomical similarities.
• About 300 million years ago amphibians split into
  two main evolutionary lines.
• One line included ancestors of reptiles, the
  other line included the ancestors of modern
  amphibians.

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From fin to limb
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B. 5 Characteristics of Modern Amphibians

• 1. Aquatic larval stage to terrestrial adult
  (metamorphosis)
• 2. Feet are webbed (if they have feet)-no claws
• 3. Thin, moist skin with no scales
• Use gills, lungs skin for respiration
• - Aquatic young use gills skin
• - Terrestrial adults lose gills, use lungs
  skin
• 5. Eggs- lack multi cellular membranes or shells
  (usually laid in water or moist place)

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C. 3 Orders of Modern Amphibians (about 4,500
species)

• 1. Anura - includes frogs and toads
• 2. Caudata - salamanders and newts
• 3. Gymnophiona - includes caecilians (legless
  tropical amphibians) (worm-like)

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1. Order Anura

• Frogs Toads
• Found worldwide
• Adapted for jumping
• anuran means tail-less (no adults have tails)
• Larvae are herbivores. Adults are carnivorous
  and will eat any animal they can capture
• Frog Toad are not formal, scientific groups
• Frog refers to smooth, moist skin
• Toad refers to rough, bumpy skin
• There are 12 families. (see following pages)
• http//www.abdn.ac.uk/nhi708/classify/animalia/ch
  ordata/amphibia/anura/

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• Family AscaphidaeAscaphids 4 speciesMembers of
  this family have ribs and rudimentary
  tail-wagging muscles. There are two genera, one
  in New Zealand and one in North America.
• Family PipidaePipid toads 15speciesThese toads
  are entirely aquatic. Only the larvae have ribs.
  Both jaws are usually toothless. and all species
  are tongueless . Eyelids are sometimes present.
• Family DiscoglossidaeDiscoglossids 10
  speciesDiscoglossids, found in Europe and Asia,
  have toothless lower jaws, and their ribs are
  present throughout life.

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• Family RhinophrydinaeThere is one
  speciesMexican burrowing toad, Rhinophrynus
  dorsalis found among scrub and savanna on the
  coastal plains of Mexico and Guatemala.
• Family PelobatidaePelobatids 54 speciesThese
  small toads with minute teeth are found in
  Eurasia, North Africa and North America
• Family BufonidaeToads 300 speciesThe toads in
  this family have no upper teeth.

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• Family AtelopodidaeAtelopodids 26 speciesThere
  are only two genera in this family of small,
  brightly coloured frogs, which live near forest
  streams in Central and South America.
• Family HylidaeTree frogs almost 600
  speciesTreefrogs are adapted for life in trees,
  and have extra cartilage between the two end
  digits of the hands and feet, which gives them a
  better grip.
• Family LeptodactylidaeLeptodactylids 650
  speciesMembers of this family are found in South
  and Central America, Australia and southern
  Africa. Several genera are adapted to the more
  arid areas of Australia. During the dry season
  they retire deep into the ground. Some species
  lay their eggs in burrows and rely on rainfall
  for development the tadpoles' metamorphosis is
  so rapid that they become adults before the water
  evaporates.

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• Family RanidaeFrogs hundreds of speciesThis
  group, which occurs on all continents, is
  unspecialised except for jumping - the
  specialisation common to all anurans.
• Family RhacophoridaeOar-legged frogs hundreds
  of speciesThese frogs, found in the tropics of
  Africa, Madagascar and eastern Asia , resemble
  tree frogs in their adaptations to living in
  trees. They have webbed hind feet.
• Family MicrohylidaeMicrohylids hundreds of
  speciesThis little-known family of burrowing and
  tree living forms is found in the Old and New
  World tropics, except western africa. The
  tadpoles hatch either at an advanced stage or
  completely metamorphosed

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Differences/Similarities-Frogs Toads
http//www.enchantedlearning.com/coloring/amphibia
ns.shtml
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Cane Toad(The Unwanted Amphibian)

• Also called the Giant Toad
• Sprays poison out of it neck is
• covered with poisonous mucus.
• Until 1935 Australia did not have any toad
  species- the cane toad was introduced to combat a
  pest -sugar cane beetles . The toads cant jump
  very high did not eat beetles that were higher
  on plants- so they didnt actually get rid of the
  beetles.
• What they did do was mess up the ecosystem-
• Fish who eat the tadpoles die.
• Animals who eat toad adults die.
• The museums have plenty of snakes preserved in
  jars which were killed by toad toxin so fast, the
  toad is still in their mouths unswallowed.
• Local vets report that a couple dogs a month are
  brought in ill just from "mouthing" toads or from
  a toad fouling their waterdish.

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American Toad

• Very common in North
• America PA
• Warty skin contains glands
• that produce a poisonous milky
• fluid, protection from predators.
• Females lay their eggs in freshwater.
• Hatching occurs 3 to 12 days after,
• depending on the temperature of the water. The
  tadpoles group together and feed and grow for 40
  to 70 days.
• The sexes can be distinguished in two ways
• Males have dark colored throats, of black or
  brown, while females have white throats and are
  lighter overall.
• female American toads are larger than males.

http//animaldiversity.ummz.umich.edu/site/account
s/information/Bufo_americanus.html
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2. Order Caudata

• Salamanders (also called newts).
• Amphibians that retain their tail as an adult.
• Salamanders look like lizards without scales.
• May be fully aquatic, fully terrestrial, or
  amphibious.
• Some have no lungs, and respire through their
  skin only.
• Reproduction
• Many reproduce in water.
• Some reproduce on land, with no swimming larval
  stage.
• Larvae and adults are carnivorous.

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Cool Salamanders
Marbled salamander
Cave salamander
Dusky salamander
Green Salamander, Aneides aeneus
www.naturalsciences.org/funstuff/notebook/her...
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Salamanders of PA
http//www.fish.state.pa.us/education/catalog/sala
mandersofpa.htm
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PA Hellbender
Salamanders that have four legs, a flat head, a
paddle-like tail, beady little eyes and are
called names like "snot otter" and "devil dog"?
One of the largest salamanders in the world,
rivaled only by their cousins in China and Japan.
Once thrived in thousands of pristine streams
throughout the eastern United States.  Today,
hellbenders are limited to relatively few healthy
stream systems, mainly in areas that have
remained isolated from human settlement.
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3. Order Gymnophiona

• Includes Caecilians (legless
• amphibians that resemble small snakes).
• Most are burrowing. They have small eyes beneath
  skin or bone, and are often blind.
• All are carnivorous.
• All are thought to have internal fertilization.
• Some lay eggs which the female guards, others
  develop inside the female.

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There are about 50 species of caecilians

• phylum -Chordata,
• subphylum -Vertebrata,
• class -Amphibia,
• order -Gymnophiona,
• family Caecilidae
• All have teeth.
• Chemosensory detection
• of prey
• In a few species, young are born alive.
• The young develop in the mother use their jaws
  to scrape secretions, called uterine milk from
  the walls of the female reproductive tract

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II. Amphibian Systems
We will especially examine structures that are
adaptations to living on land

• A Skin- no scales, moist, slimy, part of
  respiratory system
• B. Skeleton- supports body against pull of
  gravity
• C. Circulatory- 3 chambered hear, 2 circuit
  system
• D. Respiratory larvae (gills skin) adult
  (lungs skin)
• E. Digestive large elastic esophagus
  stomach- for carnivores swallowing food whole.
  See parts.
• F. Excretory- in adult- kidney ammonia (which
  is secreted as waste in fish amphibian larva)
  is transformed to urea
• G. Nervous- 4 lobes sensory organs
• H. Reproduction- depend on water, most external
  fertilization, metamorphosis.

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A. Amphibian skin -2 important functions

• 1. Respiration
• -permeable to gases and water.
• -Mucous glands secrete a lubricant that keeps the
  skin moist in air.
• 2. Protection
• -barrier from infections
• -secretes a foul-tasting or poisonous mucus that
  protects amphibians from predators.

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B. The skeleton -supports the body against the
force of gravity on land.

• Vertebrae interlock form a strong, rigid
  structure.
• Strong limbs -standing, walking jumping.
• Pectoral pelvic girdles transfer weight to the
  limbs.

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C. Circulatory System

• The frog heart has 3 chambers
• -2 atria
• -1 ventricle.
• -Though sharing a common chamber, oxygenated
  blood returning from pulmonary system has MINIMAL
  MIXING with deoxgenated blood returning from
  body.

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Circulatory system has 2 loops

• 1. Pulmonary circulation - carries deoxygenated
  blood from the heart to the lungs and back to the
  heart.
• 2. Systemic circulation - carries oxygenated
  blood from the heart to the body and back to the
  heart.
• Note
• Fish have 2 chambers (and blood with Oxygen or
  returning from body is mixed)
• Mammals birds have 4 chambered hearts.
• What advantages does a higher chambered, 2 loop
  circulatory system give ?

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Advantages of higher blood Oxygen content.

• In amphibians- which are still cold-blooded
  animals, separation of blood into 2 loops gives
  the advantage of higher oxygen content over fish
  (which have 1 loop a 2-chambered heart)
• In birds mammals-The even larger oxygen supply
  allows these warm-blooded organisms to achieve
  thermoregulation (body temperature maintenance).
• Note that in humans our RBC are de-nucleated-
  giving even more O carrying capacity to blood
  cells.

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D. 2 Forms of Respiration

• Pulmonary respiration - respiration through the
  lungs
• Cutaneous respiration - respiration through the
  skin

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E. Digestive System

• Parts include
• Pharynx,
• Esophagus
• Stomach
• Accessory Glands
• Liver
• Gallbladder
• Small intestine
• The upper part of the small intestine is the
  duodenum.
• The coiled middle portion of the small intestine
  is the ileum.
• A membrane that holds the small intestine in
  place is called the mesentery.
• Large intestine
• Cloaca
• Waste materials are stored in the cloaca and exit
  the body through the vent.

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Frog Internal Anatomy
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Do frogs have teeth?

• Actually, yes! But not like
• in this silly picture!
• Most frogs do in fact have teeth of a sort. They
  have a ridge of very small cone teeth around the
  upper edge of the jaw. These are called Maxillary
  Teeth.
• Frogs often also have what are called Vomerine
  Teeth on the roof of their mouth.
• The teeth are used to grip prey- NOT CHEW- frogs
  swallow prey whole.
• Toads do not have teeth.

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F. Excretory System

• Kidneys
• primary excretory organ
• filter nitrogenous wastes from the blood.
• Nitrogenous wastes are converted from ammonia to
  urea which is highly concentrated and helps
  conserve water.
• Wastes water urine.
• From the kidneys, urine flows to the cloaca out
  of body.

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G. Nervous

• Brain
• optic lobes -sight
• olfactory lobes -smell.
• cerebrumbehavior/learning.
• cerebellum -muscular coordination.
• medulla oblongata -controls heart rate and
  respiration rate.
• Sensory organs
• Nictitating membrane -a transparent moveable
  membrane that protects the eye.
• Sound is detected by the inner ear.
• tympanic membrane, or eardrum,
• columella, a small bone

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Frog nervous system
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Frog Dissection Sites

• http//www.ofsd.k12.wi.us/science/external.htm

http//biology.about.com/od/onlinedissections/ig/F
rog-Dissection-Images/index_g.htm
a. Large intestineb. Small intestine1. Lung
lobes2. Heart3. Liver lobes4. Gall bladder5.
Stomach6. Small intestine7. Testis8. Fat
body9. Urinary bladder
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H. Reproduction

• Mating
• Females only respond to males of the same
  species.
• Male clings to female in embrace amplexus
• Eggs and sperm are released into the water.
• Fertilization is external.
• Note- it is not always easy for a male to ID a
  female. If a male accidentally grabs a male- he
  makes a release call. The lack of a release
  call plus plumpness (signifying eggs) means
  female to a male frog. One researcher
  discovered a frog with an amplectic grip on a
  floating crab apple
• (It was plump had no release call)

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Breeding

• Frog and toad species
• each have a distinctive call to attract females
  to breeding areas.
• In shallow waters fertilized eggs will hatch into
  tadpoles and metamorphose into young frogs
• Salamanders
• nocturnal migration from upland wooded areas to
  ponds, marshes, and lakes.
• Males- do not have breeding calls. Just show up
  at the breeding areas a day or two after the
  females to start courtship.

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Metamorphosis

• The tadpole grows and slowly changes from an
  aquatic larva into an adult in a process called
  metamorphosis.
• Metamorphosis is controlled by a hormone called
  thyroxine.

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Parental care

• Some species guard their eggs until they hatch.
• Increases the likelihood that the offspring will
  survive.
• Some species sit on their eggs to prevent them
  from drying out.
• The male Darwins frog carries the eggs in his
  vocal sacs until the larvae finish metamorphosis.
• Female gastric brooding frogs swallow their eggs
  and the larvae mature in the stomach.

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Surinam Toad

• After mating, the male presses the eggs onto the
  females back
• The eggs grow into toads under the skin on her
  back then break out of the mothers skin with
  their front legs when ready.

www.honoluluzoo.org
www.molvray.com
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• Click here to see here common northern USA
  frogs toads (remember not to go thru firefox)
• http//dnr.wi.gov/org/caer/ce/eek/critter/amphibia
  n/frogident.htm