Hamline University Graduate School
St. Paul, Minnesota

Hamline University Graduate School
St. Paul, Minnesota

"cold blood"
cold blood ††††††††††††† cold blood
smooth 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


Frogs and Toads
14 species in MN,
13 species in

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MN Frogs and Toads

Why We Care
Anurans are a part of the planetís bio-diversity.

Why We Care

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
extra or missing limbs
branching limbs
spikes or protuberances
missing eyes
abnormal webbing

Internal Malformations

Malformed Frog Pictures

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Causes of Malformations
genetic origins
parasite disruption of limb formation
chemical contamination
ultraviolet radiation
physical trauma (predation,
†† people)

Trematode (flatworm) cysts have been demonstrated to cause problems in limb bud development in tadpoles

Slide 23

Possible Chemical Contaminants
heavy metals
acid rain
chlorofluorocarbons (CFCs)

Types of Agrochemicals
†††††† propylthiourea

Types of Agrochemicals
applications of the herbicide atrazine have led to egg mortality and tadpole deformities (Hazelwood 1970)

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

Global Population Declines
Increasing ultraviolet radiation
Pollution by chemicals
Acid rain
Introduction of non-native species