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Hamline University Graduate School
St. Paul, Minnesota
Frogs as Bio-indicators
Joan Chadde, MI Technological UniversityTony P. Murphy, Hamline University
Kristin Schuster, Houghton Middle School
Hamline University Graduate School
St. Paul, Minnesota
What are we being told by:
Amphibian (frog and toad) malformities
Amphibian populations locally and globally
But first……
cold blood cold bloodsmooth or slimy skin warty and dry skin strong, long legs and stubby bodies with short
webbed hind feet hind legs two bulging eyes parotid glands behind
eyes
lay eggs in clusters lay eggs in long chains a group of frogs is called a group of toads is called
an ARMY of frogs a KNOT of toads
Vs.
Frogs have: Toads have:
Anuran Diversity
14 species in MN,
13 species in MI
Frogs and Toads
92 species in USA
3,300 species in the world
MN Frogs and Toads
Why We Care
1. Anurans are a part of the planet’s bio-diversity.
2. Anurans interact in interesting ways with each other and the environment, i.e. both prey and predators
Why We Care
3. Anurans 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
Where have all the frogs gone?
Global Anuran 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