Factors Influencing Salamander Metamorphosis
Targets and Assessment
WA Science Standards Addressed:

9-12 INQB Investigate

9-11 ES2D

9-11 LS1A

9-11 LS2A
Assessments:

Rubric, presentation
Lesson Parameters
Content Area: Biology
Overview: Observe environmental factors influencing salamander metamorphosis and how a hormone can induce
widespread change
Grade Level: 9-12
Suggested Time: at least one month in total
Special Materials:
Facultative transforming salamanders, Thyroxine, Aquaria, air supply, salamander food, reliably safe water, and airlines
Learning Outcomes:
Knowledge: Students will be able to state how environmental factors influence the life history of facultative transforming salamanders, why it is important, the effect of environmental contaminants on these processes, and how these issues relate to humans.
Skill: Students should be able to collectively to complete a variety of responsibilities. Salamanders require daily care, including water treatment, feeding, and health monitoring. Students are also responsible for data collection, measurements, observations, and note taking. Students should learn about and/or understand the basic tenets of the scientific method.
Science Concept Background:
Some species of salamanders have two life histories: they may remain aquatic, retaining many juvenile characteristics, or they may metamorphose into terrestrial adults. The aquatic adults, called neotines, utilize gills for gas exchange, but terrestrial forms lose their gills completely. The ratio of neotines versus terrestrial adults varies and correlates to the habitat. Higher elevation montane populations have a higher proportion of neotines than their lower elevation counterparts. Some populations, living in ephemeral streams or ponds, will have nearly 100 percent transformation. The purpose of this lab is to test the effect of low dissolved oxygen levels on northwestern salamanders, Ambystoma gracile. Additionally, we measured the time to transformation and ratio of individuals treated with the hormone thyroxine. Thyroxine is a common vertebrate hormone known to induce transformation in other ambystomid species.
Materials:
Juvenile facultative transforming salamanders – we used a sample size of 6 for each treatment – salamanders can be collected locally or purchased from one of the suppliers
Set up at least two treatments. We used three treatments: control, low dissolved oxygen (DO), and a hormone treatment.
Aquaria – at least 3 liters each – equal to the total number of individuals
Sterilized water
Fungus treatment – we used Kordon Rid-Fungus
Ammonia remover
Air supply for the control group – or change water more frequently
Author: Jack Lester, Yakima WATERS Project, CWU, 2009-2010

Dissolved oxygen conductivity monitor
Containers for water storage
Earthworms and crickets
1 inch thick sponges or something else to provide terrestrial refuges
Procedure:
This is the outline of our particular procedure:
-Set up 18 aquaria – 6 control, 6 hormone treatment, and 6 low DO treatment. Provide a terrestrial refuge for each aquarium
-Provide air to the 6 control and 6 hormone treatment groups, or change the water frequently to maintain an average D.O. of at least 7 mg/l
-Do not change the water in the low D.O. treatment group, to maintain low D.O. Use an ammonia remover to prevent mortality due to ammonia concentration
-Feed salamanders at least twice a week. Cut earth worms into several pieces for the aquatic salamanders, and provide crickets for the transformed individuals.
-Measure the D.O. levels daily
-Take daily pictures of each salamander to track changes in morphology. Focus the pictures on the head area
-Take daily Measurements of the tail height directly behind the vent of each salamander
-Collect data for at least a month to ensure full transformation of all individuals destined to transform
-Add for µg/l of Thyroxine to each hormone treatment aquarium. Maintain this concentration throughout the experiment.
Key questions:
-What transformation ratios do you predict for each treatment group and why?
-Which factors do you think influence salamander transformation?
-Why is the ability to have two different possible life histories important?
-What types of advantages does this ability yield?
-Is this ability unique to salamanders?
-How might environmental contaminants, such as pesticides and herbicides, influence salamander transformation?
Teaching Tips:
-Prepare students for the possibility of mortality. They need to understand that this is an issue with research as it can be very stressful for the subjects being studied.
-Naming the salamanders seems to be an effective way to make the students more accountable for the wellbeing of the salamanders and the responsibilities of the research. However, this can be a problem as it relates to mortality.
Supplements:
Students should already have been exposed to text and lectures about homeostasis, evolution, natural selection, and endocrinology.
Author: Jack Lester, Yakima WATERS Project, CWU, 2009-2010

Teacher Name: __________________________
Student Name: _________________
CATEGORY
Experimental
Hypothesis
Conclusion
Scientific
Concepts
Hypothesized relationship between the variables and the predicted results is clear and reasonable based on what has been studied.
4 3
Hypothesized Hypothesized relationship between the variables and the relationship between the predicted results is reasonable based on general knowledge and observations.
variables and the predicted results has been stated, but appears to be based on flawed logic.
2
No hypothesis has been stated.
1
Conclusion includes whether the findings supported the hypothesis, possible sources of error, and what was learned from the experiment.
Conclusion includes whether the findings supported the hypothesis and what was learned from the experiment.
Conclusion includes what was learned from the experiment.
No conclusion was included in the report OR shows little effort and reflection.
Answers illustrate an accurate and thorough understanding of scientific concepts underlying the lab.
Answers illustrate an accurate understanding of most scientific concepts underlying the lab.
Answers illustrate a Answers limited illustrate understanding of scientific concepts underlying the lab.
inaccurate understanding of scientific concepts underlying the lab.
Author: Jack Lester, Yakima WATERS Project, CWU, 2009-2010