Comb jelly

Comb Jelly

Latin name: Ctenophores
Global Distribution: Worldwide
UK Distribution: Recorded off the west and northern coasts of Scotland and the coasts of Wales. Possibly under recorded.
Size:  A few millimeters to up to 1.5 meters long
Diet: larvae, rotifers, small crustaceans
Habitat: Coastal and oceanic waters

Although comb jellies look like jellyfish, they actually make up a group called Ctenophores (“tee no fours”) which means comb bearing in Greek.  The most distinctive feature of comb jellies is, not surprisingly, the “combs” that run down the side of its body. There are usually eight combs and the teeth of these combs are called cilia. These are used for swimming. Comb jellies are the largest organisms to use this method of movement. The rainbow effect that is seen during the day travelling up and down the side of a comb jelly is caused when the cilia move slightly out of sync with the next. This causes a scattering of light making them look like out-of-this world spaceship.

All comb jellies are predatory, taking plankton from the water column by swimming mouth first. They use an organ called a colloblast that squirts a glue like substance onto the prey. When food is plentiful, a comb jelly can eat up to ten times its own body weight in one day! For a long time it was thought that nothing ate comb jellies because of their low nutrient value. However, it has since been discovered that some fish species, turtles and jellyfish predate upon them.

Fun facts

  • One comb jelly species, Mnemiopsis leidyi, decimated the fisheries of the Black Sea when it was introduced, eating both fish larvae and the food of adult fish. Ironically it was another invasive comb jelly, Beroe ovata, that brought M. leidyi populations under control.
  • Comb jellies are entirely soft-bodied today, but their ancestors from ½ billion years ago had hard skeleton structures.
  • One comb jelly subgroup, Nuda, have no tentacles at all and look like a swimming mouth (like a natural pac-man) that can “bite off” pieces of prey.