Take one apart, gently
An animal with no brain, no bones, no blood and no sting — yet one that rows on beating hairs and splits daylight into a running rainbow. Poke around its parts, then take the controls of its light.
Interactive anatomy
A single grain of mineral — the statolith — balances on four tufts of cilia at the top of the animal. It's the comb jelly's sense of up and down, and the metronome that keeps all eight comb rows beating in time. It is the closest thing a ctenophore has to a brain.
Also called the apical organ. Sits at the aboral pole — the end opposite the mouth.
The light lab
The rainbow isn't a glow — it's daylight, split by rows of beating hairs. Speed the combs up or slow them down, swing the light around, then flip off the houselights to see what the animal does in the dark.
Faster cilia send the rainbow racing down the body in tighter, brighter bands.
Diffraction colour depends on the angle between the light, the combs and your eye. Move the light and the rainbow shifts.
What you see is structural colour. Thousands of long cilia, beating in waves, act like a moving diffraction grating — bending ordinary daylight into a spectrum, the same way a CD or soap bubble does. No light is made; it's borrowed and split.
In darkness a jostled comb jelly answers with its own blue-green flash, made by calcium-triggered proteins called photoproteins. A separate trick entirely — and most species really can do it, though a shimmering few, like Pleurobrachia, cannot.