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- Compass jellyfish, foto fitis, sytske dijksen
Jellyfish
Jellyfish are coelenterates which spend most of their lives as free-floating bodies with drift the current. They can only actively move a limited amount by contracting their bell-shaped hood. Because they cannot swim against the current, they are categorized as zooplankton. A jellyfish is a simple animal, 98% of it consisting of water. All jellyfish have stinging cells, but only a few species can penetrate human skin. When these stinging cells touch you, it feels like you came into contact with a bunch of stinging nettles.
- Dutch species
- Rhizostoma octopus, foto fitis, sytske dijksen
There are five jellyfish species found along the Dutch coast: the moon jelly, blue jellyfish, the lion's mane jellyfish, the compass jellyfish and the rhizostome jellyfish. The sea gooseberry looks a lot like a jellyfish but doesn't have stinging cells. It forms an entirely separate animal group. Sometimes, you also find a by-the-wind sailor on the beach, a Coelenterate that resembles a jellyfish but is not.
- Life cycle of the jellyfish
- Moon jellyfish, juvenile, foto fitis, sytske dijksen
Jellyfish begin their life attached to the ground, as a polyp. Small jellyfish eventually evolve from these polyps, which release themselves from the polyp when circumstances are favorable. From that moment on, they develop quickly and sway freely in the water.
Male and female specimen emit their reproduction cells into the water simultaneouslyso that fertilization occurs outside of the jellyfish. The fertilized egg cell does not produce a jellyfish as found on the beach, but a larvae which attaches itself to a hard surface. Every jellyfish has its own season. All of the species found in the North Sea grow no older than a year.
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