TITLE: A low cost time-lapse imaging system for Hydra
AUTHORS: Callen Hyland

[DESCRIPTION]
Hydra is a genus of freshwater cnidarian polyp known for their ability to regenerate their entire body from tissue pieces. Despite their simple body plan and tissue organization, Hydra is capable of complex behaviors, including capturing and consuming live prey, somersaulting locomotion, and phototaxis. Hydra make ideal model organisms for college and high school biology labs because they are easy to grow in large numbers and regeneration experiments can be carried out with minimal resources. The inexpensive setup described here allows time-lapse imaging of the behavior of Hydra, or other small invertebrates, with a cell phone camera. An imaging chamber is constructed out of cardboard. The sample is illuminated by a USB-powered LED panel and magnified by an inexpensive plastic lens. We also provide example movies and instructions for importing cell phone videos into ImageJ.

[BEFORE_START]
Assemble and test the imaging chamber before starting an experiment.

[GUIDELINES]
For general guidelines for maintaining, working with and disposing of Hydra, please see Low Cost Methods for Hydra Care.

[STEPS]
SECTION: Assemble the imaging chamber
8. Cut the vinyl sheet to 84 mm X 100 mm and adhere to the LED light panel. You can use the lightpanel_film.svg file with a Cricut cutter.

 

 

SECTION: Assemble the imaging chamber
1. Cut all cardboard panels for the outside of the imaging chamber. You can use the *.dxf files with a laser cutter or Cricut cutter. If you are using a boxcutter or scissors, print out the *.pdf files, cut out the shapes, and use these to draw outlines on the cardboard to be cut.

 

SECTION: Assemble the imaging chamber
2. Glue the light panel support to the base, making sure it's centered. This creates the base assembly.

 

SECTION: Assemble the imaging chamber
3. Optional: add four rubber bumpers to the corners of the base. This will keep the imaging chamber from moving on the bench.
SECTION: Assemble the imaging chamber
4. Glue the lens spacer to the phone platform centering the holes.

 

SECTION: Assemble the imaging chamber
5. Position the lens inside of the lens spacer with the concave side facing away from the phone platform.

 


 

SECTION: Assemble the imaging chamber
6. Glue the lens support to the lens spacer, securing the lens between the lens support and the phone platform. Be careful not to get glue on the lens. This creates the phone support assembly.

 


SECTION: Assemble the imaging chamber
7. Assemble the walls of the chamber. Make cuts halfway through one wall of the cardboard to fold the flaps to contact the long sides of the walls. This creates the chamber walls assembly.

 

SECTION: Image a sample
9. Place the light panel on the base assembly, connect the micro USB cable, and plug the cable into the wall adaptor. Turn on the light panel.

 

SECTION: Image a sample
10. Place the Hydra in a petri dish with Hydra medium and place the dish on light panel, then place the chamber wall assembly on the base assembly.

 


SECTION: Image a sample
11. Place the phone platform assembly on top of the chamber walls.

 

 

SECTION: Image a sample
12. On your phone, open the camera app or LapseIt time-lapse app. With the phone's camera centered on the lens, move the phone platform until the sample is centered on your phone's screen.

 

SECTION: Image a sample
13. Set the desired time-lapse parameters on your phone and start the acquisition. The example movie below was acquired with the LapseIt app with 5 second interval for 30 minutes.

 


 

SECTION: Optional: calibrate distance
19. Take a picture of a ruler with millimeter scale using the same camera settings as your time-lapse acquisition. Import the image into FIJI.
SECTION: Import video into FIJI
14. The iPhone camera app exports time-lapse movies in *.mov format and LapseIt exports movies in *.mov or *.mp4 format. Follow these steps to import movies in these formats into FIJI.
SECTION: Import video into FIJI
15. Open FIJI. Go to the Help menu and select Update.

 

SECTION: Import video into FIJI
16. Add FFMPEG to the list of sites FIJI will download updates from. After the updater finishes running, click Manage Update Sites. From the list, check the box next to FFMPEG, then Apply and Close.

 

SECTION: Import video into FIJI
17. Close and restart FIJI. Go to the File menu. Select Import -> Movie (FFMPEG). This option will only be available after FFMPEG is added to the list of update sites.

 

SECTION: Import video into FIJI
18. Navigate to your movie file and click Open.
SECTION: Optional: calibrate distance
20. Zoom in on a centimeter in the middle of the field of view. Use the line tool to measure the number of pixels in one centimeter. Draw the line from the center of one centimeter line to the next.
SECTION: Optional: calibrate distance
22. Open your time-lapse movie or image. The scale you set should be applied to the new image.
SECTION: Optional: calibrate distance
23. Optional: add a scale bar. Use the rectangle tool to draw a rectangle approximately where you want the scale bar. Go to Edit -> Selection -> Specify. Check the Scaled Units (mm) box, then adjust Width, Height and X and Y coordinates to have the scale bar with the size and position that you want, then click OK.

 

SECTION: Optional: calibrate distance
24. Use Ctrl + F to fill in the rectangle to create the scale bar. Colors for filled shapes can be adjusted by going to Edit -> Options -> Colors.

 

SECTION: Optional: calibrate distance
21. Go to Analyze -> Set Scale. The length in pixels of the line you drew should be filled in. Change the Known Distance to 10 and the Unit of Length to mm. Check the Global box.