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THE JELLYFISH FILE
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If they all weighed 250kg and had 20m tentacles, as some do, diving might be less popular. Paul Naylor reports
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ARTFUL DODGERS
While jellyfish tentacles spell doom for many small fish, young whiting often live among them for protection. How the whiting avoid being captured is a bit of a mystery. It has been suggested that, rather than being immune from the sting, they are just incredibly adept at dodging the tentacles!
TAKING FIVE
Most jellyfish stop drifting for part of their lives. Their larvae fix themselves to the seabed to form a sessile phase which then buds to produce numerous tiny jellyfish that float off to become adult drifters.
PARTING GIFTS
The stinging capsules of jellyfish still function even when separated from their owner. Fragments of tentacles, left on buoy ropes, for example, retain their stinging power, as anyone who has handled such ropes and then rubbed their face well knows.
DRIFTING STINGERS
Jellyfish can be thought of as swimming sea anemones and, along with the corals, belong to the same major group of animals. They are all distinguished by having a central mouth, surrounded by tentacles which bear large numbers of stinging capsules or cnida, after which the group (Cnidaria) is named.
GENTLE GIANT
The largest jellyfish we usually encounter is Rhizostoma octopus. It lacks the usual feedingtentacles (and also an English name!) and lives on plankton. Often found near the surface, it will apparently move into deeper water when disturbed by rain or the noise from passing ships.
FOOD CHAIN
Most jellyfish can catch substantial prey such as fish in their tentacles, using the stinging capsules to stun and ensnare unlucky victims. Some species also use sheets of mucus on their bodies to trap small prey, the food-bearing mucus eventually being passed to their mouths, like flypaper on a conveyor belt.
LION KING
The UK jellyfish with the fiercest sting is the lion's mane, (pictured). Individuals of this species up to 2m in diameter, with tentacles more than 20m long, and thought to weigh more than a quarter of a tonne, have been recorded in the Arctic Ocean. Thankfully, most lion's manes found near the UK are much smaller. |
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