Swarm of jellyfish

Jellyfish are cnidarians and during the summer can appear in vast quantities along the Swedish west coast. Many get washed up onto the beaches and die. How is it that during the winter they are not seen and turn up in such numbers during the summer? This is due to the jellyfish having two different stages in its life-cycle, a polyp and a medusa stage. The polyp stage is small and can with certain specie span over a few years. The polyps bud off from the medusae and seldom survive more than one season.
    The medusae drift with the sea currents because they swim slowly. Their rythmic swimming motion occurs when the muscles pull the body together and the elastic jelly stretches it out again.
    Jellyfish live off the animals they catch with their stinging cells. Large jellyfish can catch other jellyfish and fish, but most specie live on small organisms suspended in the surrounding waters.

stalked jellyfish

A 3 cm large stalked jellyfish, Haliclystus auricula.

A special type of jellyfish is the stalked jellyfish which does not have a medusa stage. The polyps live firmly rooted on algae and are distributed as larvae.
    The jellyfish group comprises about 14 specie in Swedish waters and about 200 specie world-wide.
    Read more about the different jellyfish!

Previous page

Page 7 of 13

Next page

Home    Contents    Inspiration    Facts    Collaboration   
© Aquascope 2000   Tjärnö Marine Biological Laboratory, Strömstad, Sweden
Bo Johannesson | Martin Larsvik | Lars-Ove Loo | Helena Samuelsson