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) malformitiesAmphibian populations locally and globallyBut 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 Care1. 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 Care3. 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

• 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

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