the biggest jelly in britain?
The honour of being the largest cnidarian in British waters is fought over by two jellyfish. Rhizostoma octopus has a bell which can grow to an impressive diameter of 1 m. However, although the lion’s mane jellyfish Cyanea capillata (above)has a bell only as wide as 50 cm, its tentacles grow to an amazing 13 m in length.
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The name "Cnidaria" (pronounced with a silent ‘c’ as in: Ny-dare-ree-ah) comes from the Greek word knide meaning "nettle" - and all species in this group can sting. They possess 'nematocysts', stinging capsules present within the cells of the tentacles and other parts of the body. Almost all are found living in the sea, though a few live in freshwater habitats.
There are three main classes of cnidarian:
- anemones and corals (Anthozoa)
- hydroids (Hydrozoa)
- jellyfish (Scyphozoa)
Worldwide. there are about 10.000 species which belong to the group, though more are being discovered all the time.
- Some cnidarians are very small and may only be seen properly with the use of a microscope; whilst others, particularly the massive reef-building corals, may build structures several metres in diameter.
- Cnidarians may exist as solitary or colonial forms. The two main structural forms are the polyp (polypoid form) and the medusa (medusoid form).
- Most species exhibit some form of radial symmetry, and possess a ring of tentacles around the mouth area.
- Most cnidarians are carnivorous with their main prey items being small crustaceans.
- Jellyfishes and anemones feed by catching prey with their tentacles, when batteries of nematocysts are stimulated to fire. The tentacles then retract and bring the prey to the mouth.
What eats jellyfish?
You migh be surprised, but lots of animals eat jellyfish - including leatherback turtles, basking sharks and sunfish
