Written by Jonathan Wojcik
Equally bizarre are the Platyctenida, combless comb jellies who live more like slugs or flatworms, creeping along what would normally be the interior lining and "mouth" of other ctenophores. Trailing their tentacles in the water to trap plankton, some species are domed and "horned" like these while many others are perfectly flat, often living harmlessly on the bodies of sea stars, cucumbers, corals or sponges where they look like little more than colorful patches of skin.
While by no means the weirdest or most elaborate, the Beroid comb jellies are my personal favorites, and I'm sure you can see why. Completely lacking tentacles or colloblasts, these swimming mouths prey exclusively on other comb jellies, swallowing them whole or taking bites out of of them with internal "teeth" formed from modified cilia. When not eating, they "zip shut" their mouths with adhesive cells and flatten out into a faster moving shape; sleek, ravenous sharks of the jelly world.
One of the most unusual ctenophores, and the last I'll be describing, is also one of the most recently discovered and still largely an enigma; it was captured on video in 2002, but its footage wasn't viewed until 2006, and no specimens have since been recovered. Still unnamed, we only know that this species seems to hold onto the seabed by a pair of long cables, drifting kite-like in the current with its feeding tentacles held out.