Knowledge Base

Problem

Users tracking zebrafish larvae in a 24-well plate want to measure the actual body size (surface area) of detected larvae, not just positional tracking data.

Details

Symptoms: In the EthoVision XT tracking view, larvae are detected and highlighted with a yellow detection overlay, but the user cannot identify which output measure corresponds to the physical body area of the animal. Applies to EthoVision XT 17 and likely other recent versions used with DanioVision.

Solution

1. In EthoVision XT, navigate to Analysis → Select Measures (or the equivalent measure selection panel for your version).
2. Look for the measure labelled 'Body Surface Area' (or 'Subject Area' depending on EthoVision XT version) — this measure reports the pixel area of the detected subject, which corresponds to the larva's body size as seen from above.
3. Enable this measure for your experiment and re-run the analysis (or ensure it is selected before the next recording if data has not yet been collected).
4. Export the results to verify the values are plausible for your larvae at the plate magnification used.
5. If the measure is not available in your version of EthoVision XT, contact Noldus support to confirm which version introduced 'Body Surface Area' and whether an upgrade is required.