Comb Jelly (phylum Ctenophora)

InvertebrateMarinePlankton

Overview

Comb jellies (phylum Ctenophora) are delicate, transparent, gelatinous animals that drift through the world's oceans, looking superficially like small jellyfish. Their name comes from eight rows of tiny beating hair-plates, called combs (or ctenes), that run down the body and propel them through the water. As these combs beat, they scatter light into shimmering, flickering rainbows — one of the most beautiful sights in the sea — even though most comb jellies are not themselves brightly coloured.

Despite the resemblance, comb jellies are not true jellyfish; they belong to a completely separate, very ancient animal group, and unlike jellyfish they do not sting.

Note: there are many comb jelly species; details here cover them broadly. Treat general statements as approximate and verify against authoritative sources.

Habitat & Range

Comb jellies live throughout the world's seas, from coastal waters to the open ocean and from the surface down into the deep sea. Most drift as part of the plankton, carried by currents, and they can be found from the tropics to polar waters. Some are surface-dwellers; many others live in the dark depths.

Diet

Comb jellies are carnivores that feed on plankton — tiny crustaceans, larvae, fish eggs, and other small animals — and some eat other comb jellies or jellyfish. Many capture prey with sticky cells (colloblasts) on trailing tentacles, rather than the stinging cells used by true jellyfish; others simply engulf prey with a large mouth. Despite their fragile look, comb jellies can be voracious and ecologically powerful predators.

Behavior

Comb jellies are the largest animals to swim using cilia (the tiny beating combs), rather than muscles or fins, and the rainbow shimmer of their beating comb rows is simply light being split as it passes through the moving plates. Many comb jellies are also bioluminescent, producing their own blue or green glow in the dark. Most are hermaphrodites and can reproduce prolifically. Their soft, watery bodies leave almost no fossils, which is one reason their place in the animal family tree — possibly one of the very earliest branches — is still debated by scientists.

Human Interaction & Conservation

Comb jellies are harmless to people — they do not sting — and are admired in aquariums for their hypnotic shimmer. Ecologically, however, they can be powerful: one species, the warty comb jelly, was accidentally carried to the Black Sea, where it bloomed in huge numbers, devoured plankton and fish eggs, and contributed to the collapse of local fisheries — a striking example of how a delicate-looking animal can reshape an ecosystem when introduced. Consult authoritative sources for details.

More photos of the comb jelly