Arthropod Olympics
Stacked Graphs and Biophysics with Spring-Loaded Arthropods
A data activity and lesson plan made in partnership with
Teacher Note:
This activity is best used as a way for students to explore the researcher’s data like the scientists themselves. A suggested progression includes:
Have students read the Science News article and use the Science News Learning discussion to review how the research team collected data by analyzing high-speed footage.
Have students complete this DataClassroom Activity
Use the Science News Learning activity as an extension or assessment to have students design an experiment to measure another Olympic-worthy arthropod.
Background
Evolution has produced a stunning diversity of ways that an animal can move. Jumping, running, climbing, sliding, slithering, swimming, walking, and drifting are just a few of the myriad of ways that animals move through the different environments on our planet. Biomechanists are scientists that explore this diversity of animal movement in a physics-heavy branch of biology that specializes in describing the ways that animals move. Photography has long been an important tool in biomechanics studies, but high speed photography has given scientists more power than ever before to record and analyze fast animal movements in great detail.
The spinning jump of the tiny springtail, Dicyrtomina minuta, is an extraordinary example of animal movement. Most springtails are omnivors, live in moist soil and leaf litter, and can be recognized by their furca . This forked tail-like appendage protrudes from the abdomen and allows the springtail to use an incredible method of escaping predators. When a hungry spider or beetle gets too close for comfort, the springtail can launch itself spinning into the air by pushing off the ground rapidly with the furca. In doing this, the springtail launches its body into the air more than 60mm despite its 1-2mm body length, while spinning at up to 368 rotations per second. This is roughly the equivalent of a human jumping from the ground, up to the torch on the Statue of Liberty, while spinning more than 300 times faster than an olympic gymnast doing a back flip. To the predator, the springtail has just vanished into thin air!
“Fig. 1 Dicytromina minuta springtails are found in the top layers of leaf litter. (A) Light microscope image of D. minuta showing a lateral view with posterior end of the animal to the right. Anatomical reference points relevant to body orientation and jumping morphology are shown on the panel. The collophore is underneath the body and not everted and therefore not visible in the image. (B) A D. minuta springtail during a jump where the furca is pushing down on the substrate and lifting the springtail into a jump. Circles on the body represent the points tracked during a jump and used to calculate jump kinematics.” Caption from the original paper (see citation below).
Recently, a pair of scientists from North Carolina State and Georgia Tech Universities used high speed photography to record and analyze the jumping performance of a springtail. They watched the jumping motion with close-up photography that recorded the jump at an astonishing 40,000 frames per second. They then analyzed this video, capturing the motion beginning just five frames before furca release and ending just after the springtail becomes airborne, to produce numeric data that includes velocity, distance, angle, and acceleration. The scientists tracked specific reference points on the animal’s head, body, and furca (Fig. 1) within the video to get these data. They presented their findings to the world in the journal, Integrative Organismal Biology.
In this activity, you will use the actual data collected by the scientists to make graphs and describe the jumping motion of the springtail in detail much in the way that was done in the original study.
Dataset
This dataset is found in supplementary materials from the paper titled: “Jumping Performance and Behavior of the Globular Springtail Dicyrtomina minuta". Data were collected by tracking location via video analysis of springtail jumps, and turning that analysis into numeric measures of linear and angular distance, velocity, acceleration. Data were taken at time intervals of 0.03 milliseconds during the jump process, starting just before the jump begins to just after the furca leaves the ground and the springtail becomes airborne. This produced a dataset with 66 observations (rows in the dataset) covering a moment that was just 1.61 milliseconds in total.
Note that this dataset only captures the launch portion of the jump and ends at the point where the springtail leaves the ground (Fig. 2).
A A Smith, J S Harrison, Jumping Performance and Behavior of the Globular Springtail Dicyrtomina minuta, Integrative Organismal Biology, Volume 6, Issue 1, 2024, obae029, https://doi.org/10.1093/iob/obae029
Variables
Fig. 2 Liftoff process from furca release until airborne. (A) Anatomical reference points and sequential extracted frames from a single sequence captured at 40,322 frames per second showing furca release, body rotation, and initial liftoff. Time stamps indicate milliseconds relative to the last point of contact with the ground (outlined).Integr Org Biol, Volume 6, Issue 1, 2024, obae029,
Time (ms): This numeric variable is a reference point to moments during the springtail jump. The time marker t=0ms represents the moment the furca has left the table or surface the springtail was sitting on. Negative values of time are before this moment, and positive values of time indicate the springtail is fully ballistic (or airborne). Measured in milliseconds.
Distance (mm): This numeric variable describes the linear motion of the springtail, as measured from the center of mass. Measured in millimeters.
Velocity: This numeric variable represents the linear velocity of the springtail, as measured from the center of mass. Measured in millimeters/second
Acceleration: This numeric variable calculates the linear acceleration of the springtail, as measured from the center of mass. Measured in millimeters/second/second.
AngleVelocity (deg/s): This numeric variable indicates the angular velocity of the rotating springtail. Measured in degrees/second.
AngleAcceleration (deg/s/s): This numeric variable measures the angular acceleration of the rotating springtail. Measured in degrees/second/second.
FurcaAngleVelocity (deg/s): This numeric variable indicates the angular speed and direction of deployment of the springtail’s furca during launch and flight. Measured in degrees/second.
FurcaAngleAcceleration (deg/s/s): This numeric variable calculates the angular acceleration of the springtails furca during deployment. Measured in degrees/second/second.
Activity
Make Predictions:
Linear velocity is how fast an object moves in a straight line (meters/sec). Angular velocity is how fast an object spins in a circle (degrees/sec or radians/sec). After watching the video above, do you think springtails move faster in terms of linear or angular velocity?
Part of this activity will explore how fast the springing mechanism (a springtail’s furca) moves to get the springtail flying. How do you think the speed of the furca’s movement will compare to angular or linear velocity it generates for the springtail?
Explore the Data:
Part 1: Linear Velocity
3. Use the graphing tools to visualize how distance changes over time. Set Distance (mm) as the y-variable and Time (ms) as the x-variable. Screenshot the graph below:
4. Describe the motion of the springtail, based on this graph. Use phrases that describe its speed and location.
5. Change your graph to view linear velocity over time. Use the graph tools and set Velocity (mm/s) as the y-variable and keep time (ms) as the x-variable. Screenshot the graph below:
6. Describe the velocity of the springtail over time during the launch, based on this graph. Use specific moments in time to help describe any changes (hint: put your mouse cursor over any of the points to see the exact time value).
7. What is the max linear velocity the springtail reaches?
8. Acceleration is defined as a change in velocity. Based on your velocity graph, where is positive acceleration taking place? If physics says you must have a force to have acceleration (F=ma), what may be happening to the springtail during that duration?
9. Let’s predict linear acceleration, using our velocity vs. time graph. Exclude datapoints (use the filter funnel option in the graph tab ) which are outside the times we predict the furca is pushing the springtail into the air. Your filter options should look something like this:
Once your filter is on, add a regression line for your smaller dataset. Screenshot your new graph below:
What on your graph represents acceleration? What is the value? Include units in your answer.
Return your graph to include all datapoints before proceeding. To do this, go back into the funnel filter and click “Clear all excludes” button.
10. Change your graph to view linear acceleration over time. Use the graph tools and set Acceleration (mm/s/s) as the y-variable and keep time (ms) as the x-variable. Be sure to undo your regression line. Screenshot the graph below:
11. Describe the acceleration of the springtail, using the data in the above graph. Discuss what’s happening between t= -1ms and t= -0.25ms. How does this relate to your prediction from #8? Does it also match your value you found in #9?
12. Discuss what’s happening to acceleration after t= -0.25ms and your prediction of what is happening with the springtail.
Part 2: Rotational Motion
13. Use the graph tools and set AngleVelocity (deg/s) as the y-variable and keep time (ms) as the x-variable. Screenshot the graph below:
14. From our earlier graphs (in part 1), we know when the furca is pushing the springtail into the air. What do you notice about the angular velocity of the springtail during this time? What do you expect the rotational acceleration graph to look like?
15. What is the max rotational velocity the springtail experiences?
16. Use the graph tools and set AngleAcceleration (deg/s/s) as the y-variable and keep time (ms) as the x-variable. Screenshot the graph below:
17. How does this graph align with your predictions in #14?
Part 3: Motion of the springtail’s spring tail
18. Use the graph tools and set FurcaAngleVelocity (deg/s) as the y-variable and keep time (ms) as the x-variable. Screenshot the graph below:
19. What is the peak angular velocity of the furca?
20. Looking back at the max velocity values we gathered from part 1, 2 and 3, rank the values from least to greatest. (Check out your answers to #7, #15, and #19).
Note: to convert angular values to linear, use the length of the springtail to be 1mm (or radius from center of mass as 0.5mm), and the length of the furca to be 0.66mm.
21. How does this match your predictions from #1 and #2?
Part 4: Full Jump Analysis
22. Below are graphs of data from a springtail’s full jump. This includes data from the launch portion (like what you analyzed above) to the point where the springtail returns to the ground.
Note: Time is delineated differently here from the “launch only” graphs of Part 1-3. No longer is t=0s the moment where the furca leaves the table. It is now the moment the furca is deployed initially.
You can see the first graph (x vs. y) displays an “image” of the jump as the springtail moved through the air, providing it’s location in x and y coordinates.
Looking at the units and axis descriptors of the second and third graph, which is showing linear velocity, and which is showing the springtails angular velocity?
23. Identify key moments of each graph (highs and lows, and what is physically happening at those moments)
Graph 1 -
Graph 2 -
Graph 3 -
24. This next set of data is from a different springtail launch. What looks different from the previous set of data and what looks the same? What might be the reason for these differences?
25. In this analysis we looked at data from just one springtail. But we know that there is variation in the natural world! If we had data from 100 springtails, what kinds of scientific questions could you answer using this kind of data (different distance, velocity, and acceleration data)? List one or two questions below.