amphibians amphibian=greek for amphibios which means double life ectothermic vertebrates hibernate...
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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
• 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
cold blood cold bloodsmooth or slimy skin warty and dry
skin
Vs.
Frogs have: Toads have:
Anuran Diversity
Frogs and Toads
92 species in USA
3,300 species in the world
Frogs and Toads
Amphibian Habitats
rivers and streams
lakes, ponds, marshes
grasslands
forests
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--amphibious2) 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
• 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
• 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
• herbicidesManeb-
fungicide
• pesticides propylthiourea
• fertilizersDr. 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• a concern during the past decade• frog declines widespread and well-
documented• 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
• 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 Froglast 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