A ctenophore drawn out into a transparent ribbon that swims by undulating its whole length.
A comb jelly flattened and stretched into a clear ribbon, a few centimetres deep and up to about a metre and a half long, swimming with a slow snake-like undulation of the whole body. The comb rows run along the two long edges, and the light from a torch breaks in them into a band of running colour that travels the length of the animal. That colour is diffraction from the beating cilia rather than pigment or bioluminescence, and it disappears when the light is moved.
The mouth sits at the middle of one long edge, and fine tentacles trail from a groove beside it and collect small zooplankton along the length of the ribbon. Disturbed hard, the animal produces its own blue-green light, which is separate from the running colour and shows in a dark frame with the strobe off.
It is a warm-water oceanic species, and on the Indo-Pacific coasts it is met on blackwater dives rather than on ordinary night dives. A whole animal is difficult to frame at this length, and most photographs are of a section of the ribbon with the comb rows lit. Small hyperiid amphipods and other riders are sometimes found on it.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
