Side split
Check the side edge of the carapace for a visible seam or opening. A more obvious split can indicate the crab is close to molt.
Visual cues to check first
These sketches are training aids for human review. Look for several cues together, then compare your read with MoltMeter and known molt timing examples.
Halo at joints
Look around leg joints and limb bases for pale rings or halos. The cue is easiest to see in good light and close views.
Shell and limb opacity
As molt approaches, shell and limbs may look duller, milkier, or less translucent. Compare against crabs from the same light and tank.
Before molt, the old cuticle separates from the epidermis, then the shell opens along a weak line when the crab emerges. After molt, the new shell is pale and soft before it hardens. In practice, the strongest reads usually come from several cues together, not just one.
Training-data examples
Examples copied from the local training dataset. Captions show source crab/date context where available.
