Bligh Pringle, of Balclutha Primary School, asks :-
What are jellyfish, how do they move and what do they eat?
Jean McKinnon, a marine biologist at the University of Otago, responded.
Jellyfish are found in all of the world oceans (and even in freshwater!). They come in a huge range of sizes from three millimetres to two metres in diameter. Some of them can have tentacles many metres long.
There are about 190 different species of jellyfish, but as we learn more about the ocean and what lives there, this number is likely to increase. In New Zealand we are most likely to see the Moon Jelly (Aurelia aurita), which is a transparent lavender-blue colour and completely harmless. The Portuguese man-o-war (Physalia physalis) is also seen around the coasts but this is not a "true" jellyfish, it is a colony of animals all living together. A true jellyfish is one animal.
Jellyfish are shaped like a disc; sometimes they are bell shaped or are like an upside down pudding bowl. They move by squeezing the bell with special muscles, which squirts water out through their mouth, this helps them move up or down in the water. Otherwise, jellyfish float with the wind and the water currents and can't really control where they go.
Jellyfish are carnivores and eat mainly zooplankton (including other jellyfish!). Big jellyfish eat large crabs and fish which they catch and kill using stings on their tentacles. In turn, jellyfish are eaten by many other marine animals, like dolphins, turtles and sunfish. Some types of jellyfish are even eaten by humans! You can get pickled jellyfish at Asian supermarkets.