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Amphibians
Amphibians
• AMPHIBIAN=GREEK FOR
AMPHIBIOS WHICH MEANS
“DOUBLE LIFE”
• ECTOTHERMIC
VERTEBRATES
• HIBERNATE OR ESTIVATE
DEPENDING ON CLIMATE
Three Orders of Amphibia
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Anura-frogs and toads
Urodela-salamanders and newts
Elongated bodies and tails
Young have gills-some adults retain
them
• Apoda-caecilians
• Tropical, burrowing amphibians
• Legless, wormlike
4 Characteristics of Amphibians
• Legs-important evolution for living on
land. caecilians have lost their legs as
they adapted to burrowing existence
• Lungs-larvae have gills most adults
breath with a pair of lungs with the
exception of lungless salamanders
• Partially divided heart-atrium is divided,
but the ventricle is not.
• Cutaneous respiration -most supplement
oxygen uptake by respiring through skin
Lungs
• Lungs are internal -allows exchange
of oxygen and carbon dioxide
between blood and air
• Greater the surface area the greater
the amount of oxygen can be
absorbed
• Lungs are not as efficient as gills, but
there is more oxygen in air than in
water so lungs do not have to be as
efficient
Double Loop
Circulation
• Due to moving to land and requiring
more oxygen for their muscles,
amphibians developed a double loop
in their circulatory system
• Amphibians have pulmonary veins
that deliver oxygen rich blood back
to the heart and then to the
remainder of the body
Double Loop Circulation
Amphibian Heart
• Sinus venosus delivers blood to the right
atrium
• Septum separates the amphibian
ATRIUM into right and left halves
• Septum prevents the mixing of oxygen
poor and oxygen rich blood
• Both types of blood are dumped into the
ventricle
• Conus arteriosus has a spiral valve that
helps to keep the blood somewhat
separate
Amphibian Reproduction
• Require water because eggs lack
shells to prevent water loss
• External Fertilization-female
releases eggs and male fertilizes
externally-called amplexus
• Complete metamorphosis-egg,
tadpole, young frog, adult frog
Vs.
Frogs have:
cold blood
smooth or slimy skin
Toads have:
cold blood
warty and dry skin
Anuran
Diversity
Frogs and Toads
92 species
in USA
3,300 species
in the world
Frogs and Toads
Amphibian Habitats
forests
grasslands
lakes, ponds, marshes
rivers and streams
Why We Care
1. Amphibians are a part of the
planet’s bio-diversity.
2. Amphibians
interact in
interesting ways
with each other and
the environment,
i.e. both prey and
predators
Why We Care
3. Amphibians provide benefits to
humans
i.e. Gastric Brooding Frog of Australia
might have provided answers for people
suffering from gastric ulcers
(Case of the Vanishing Frogs, T. Halliday and W. R. Heyer).
4. Frogs As Bio-indicators
1) double life--amphibious
2) permeable skin
3) absorb and concentrate toxins-biomagnification
4. Frogs As Bio-indicators
Biomagnification: a process in which retained
substances become more concentrated
with each link in the food chain
Malformed Amphibians
External Malformations
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extra or missing limbs
branching limbs
spikes or protuberances
missing eyes
abnormal webbing
Internal Malformations
• reproductive
• digestive
• urinary
Malformed Frog Pictures
Dr. David Hoppe, University of Minnesota-Morris
Dr. David Hoppe, University of Minnesota-Morris
Dr. David Hoppe, University of Minnesota-Morris
Dr. David Hoppe, University of Minnesota-Morris
Causes of Malformations
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genetic origins
parasite disruption of limb formation
chemical contamination
viruses
ultraviolet radiation
physical trauma (predation,
people)
Trematode (flatworm) cysts have been
demonstrated to cause problems in limb bud
development in tadpoles
Dr. Stanley K. Sessions, Hartwick College
Dr. Stanley K. Sessions, Hartwick College
Possible Chemical Contaminants
• Agrochemicals
• heavy metals
• acid rain
• chlorofluorocarbons (CFCs)
Types of Agrochemicals
• herbicides
Maneb-fungicide
• pesticides
propylthiourea
• fertilizers
Dr. Stanley K. Sessions,
Hartwick College
Types of Agrochemicals
applications of the
herbicide atrazine
have led to egg
mortality and
tadpole deformities
(Hazelwood 1970)
Dr. Stanley K. Sessions,
Hartwick College
Correlations to Human
Health Concerns
• high nitrate levels (from fertilizers) in human
drinking water and frog breeding ponds are
hazardous
• human birth defects result from pesticide
application
• UV radiation results in blindness and skin
cancer in humans and other animals; DNA
damage in developing frog eggs
Where have all the frogs gone?
Global Amphibian Decline
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a concern during the past decade
frog declines widespread and welldocumented
possible causes include habitat
destruction, increased UV radiation,
and chemical contamination
Global Population Declines
• Loss of habitat
from filling in wetlands to create
more farmland for crops, and to
build more houses and roads
(Case of the Vanishing Frogs, T. Halliday and W. R. Heyer).
Global Population Declines
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Increasing ultraviolet radiation
Pollution by chemicals
Acid rain
Pathogens
Parasites
Introduction of non-native species
Global Population Declines
Amphibian declines occurring in
locations where habitats relatively
undisturbed.
Australia:
Gastric Brooding Frog
last seen in wild in
1980s
Global Population Declines
Monteverde, Costa Rica:
Golden Toad
last seen 1988
Global Population Declines
Other places experiencing declines include:
Puerto Rico
Ecuador
Venezuela
Brazil
U.S. Rocky Mountains
Cascade Mountain Range in Washington,
Oregon, and California