Dragonflies Feeding on Amphipods; Size Does

Matter

Dragonflies Feeding on Amphipods; Size Does

Matter

Linda White, Kenny Danner, Shane Murnan, Craig Henson, and Lori

Espieg

Research Scientist: John White

Linda White, Kenny Danner, Shane Murnan, Craig Henson, and Lori

Espieg

Research Scientist: John White

Introducing…our study subject

Introducing…our study subject

We will be studying the Hylella amphipod.

We will be studying the Hylella amphipod.

Introducing…our preyIntroducing…our prey

Dragonfly nymphDragonfly nymph

Step 1 Step 1 We added 400 mL of non-chlorinated well

water to fifteen individual sandwich sized 900 mL “quart” serving containers.

We added 400 mL of non-chlorinated well water to fifteen individual sandwich sized 900 mL “quart” serving containers.

Step 2Step 2 We placed four four inch segments of

ambulia plastic aquarium plants. We placed four four inch segments of

ambulia plastic aquarium plants.

Step 3Step 3 All of the containers were left

overnight to reach ambient temperature and oxygenate the water.

All of the containers were left overnight to reach ambient temperature and oxygenate the water.

Step 4Step 4 Dragonfly larvae were separated into

individual plastic beverage containers overnight to rest. Dragonfly larvae were not fed to ensure that each dragonfly had an appetite.

Dragonfly larvae were separated into individual plastic beverage containers overnight to rest. Dragonfly larvae were not fed to ensure that each dragonfly had an appetite.

Step 5Step 5 We separated all of the amphipods into

four categories; small, medium, large, and females with broods. The females with broods were placed in a separate container.

We separated all of the amphipods into four categories; small, medium, large, and females with broods. The females with broods were placed in a separate container.

Step 6Step 6 We placed eight small, eight

medium, and eight large amphipods into each container.

We placed eight small, eight medium, and eight large amphipods into each container.

Step 7 Step 7

After allowing the amphipods to rest in the containers, we placed one dragonfly larvae in each container.

After allowing the amphipods to rest in the containers, we placed one dragonfly larvae in each container.

Step 8Step 8 After allowing nature to take its

course, we returned to examine our results.

After allowing nature to take its course, we returned to examine our results.

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Step 9Step 9 The dragonfly larvae had a bigger

appetite than expected. We found no amphipods. All of our test subjects had been consumed.

The dragonfly larvae had a bigger appetite than expected. We found no amphipods. All of our test subjects had been consumed.

Step 10Step 10 We conducted our experiment a

second time using eight of each size amphipod in each arena. We placed the females with broods in a separate container.

We conducted our experiment a second time using eight of each size amphipod in each arena. We placed the females with broods in a separate container.

Step 11Step 11 Our dragonfly larvae were left in the

arenas for twelve hours. After twelve hours the dragonfly larvae were separated from the amphipods.

Our dragonfly larvae were left in the arenas for twelve hours. After twelve hours the dragonfly larvae were separated from the amphipods.

Step 12Step 12 We placed the remaining amphipods

and dragonfly larvae in a vial with ethanol solution “killing juice” to preserve them for measuring.

We placed the remaining amphipods and dragonfly larvae in a vial with ethanol solution “killing juice” to preserve them for measuring.

Step 13Step 13 We sorted the amphipods based on

size remaining on Petri dishes for each arena.

We sorted the amphipods based on size remaining on Petri dishes for each arena.

Step 14Step 14 Using a microscope, we measured

the head length of each of the remaining amphipods.

We measured the head width of each dragonfly larvae.

Using a microscope, we measured the head length of each of the remaining amphipods.

We measured the head width of each dragonfly larvae.

Step 15Step 15 All of our data was entered into a

spreadsheet so we could draw conclusions based on our data.

All of our data was entered into a spreadsheet so we could draw conclusions based on our data.

ResultsResults We determined that the dragonfly

larvae preferred the medium size amphipods to the small or large amphipods.

We determined that the dragonfly larvae preferred the medium size amphipods to the small or large amphipods.

Number of Amphipods Remaining After Dragonfly Exposure

0

0.5

1

1.5

2

2.5

3

Small Medium Large

Size Class

Number of Individuals

Number of Amphipods Remaining After Dragonfly Exposure

0

0.5

1

1.5

2

2.5

3

Small Medium Large

Size Class

Number of Individuals

ConclusionsConclusions Through the analysis of our data, we

determined that the dragonfly larvae prefer amphipods that are medium sized.

Reasons for this could be the energy used to catch the amphipod in relation to the energy gained by consuming the amphipod.

Through the analysis of our data, we determined that the dragonfly larvae prefer amphipods that are medium sized.

Reasons for this could be the energy used to catch the amphipod in relation to the energy gained by consuming the amphipod.

Ideas for Future StudyIdeas for Future Study Comparing females with and without

broods to males of the same size. Comparing females with and without

broods. Increase the variation of dragonfly

larvae size.

Comparing females with and without broods to males of the same size.

Comparing females with and without broods.

Increase the variation of dragonfly larvae size.

More Ideas for Future StudyMore Ideas for Future Study Painting black dots on males to determine

if it increases visibility or attractiveness. Analyze energy content to determine if

females with broods provide a higher energy return for dragonfly larvae.

Introduce other predators to determine which size amphipod they prefer.

Painting black dots on males to determine if it increases visibility or attractiveness.

Analyze energy content to determine if females with broods provide a higher energy return for dragonfly larvae.

Introduce other predators to determine which size amphipod they prefer.

Potential PredatorsPotential Predators

Toe BitersCrawfishTadpolesFish

Toe BitersCrawfishTadpolesFish

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Questions?Questions?