Jellyfish, anemones and corals

Change font size:

Jellyfish, anemones and corals

Anemones, corals, jellyfishes and hydroids are collectively known as cnidarians. They are an ancient group with a history that reaches back more than 650 million years, and with over 10,000 known species. Many of these animals look very different from each other, but most cnidarians go through two basic body plans at some point in their life cycle - a free-swimming jellyfish (medusa) stage and an anemone (polyp) stage.

Bluebottles and hydroids

Bluebottles differ from true jellyfishes in several ways. The gas-filled float supports a number of specialised tentacles, which are actually members of a complicated colony. The individual members, or 'zooids', cooperate to form what looks to us like one animal. Hydroids are colonial, plant-like animals, some of which are also found in freshwater.

More about Bluebottles and hydroids
- Bluebottle

Box jellies

Cubozoans have a box-shaped bell with tentacles at each corner. They are generally strong swimmers and have painful stings. Some tropical cubozoans are among the deadliest of all venomous marine animals, including the Box Jellyfish (Chironex fleckeri).

More about Box jellies
- Jimble

Jellyfish

Scyphozoans are members of the Phylum Cnidaria and are sometimes referred to as 'true jellyfish'. The free-swimming medusa form is the dominant life stage for this group, while the polyp form is a juvenile stage for many.

More about Jellyfish

Anemones and corals

The Class Anthozoa contains the sea anemones and corals. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Some anthozoans can reproduce asexually by budding.