Lifestyles for Better Living

Moon Jellyfish

Aurelia aurita, or the moon jellyfish is one of the more common species and is sometimes known as the saucer jellyfish as well. In this group of jellyfish there are more than 10 different species that are almost identical and it is therefore quite difficult to distinguish one from another.

The Medusa, or bell of the moon jellyfish is of a translucent colour, usually white with a blue or pink tinge. One way to distinguish this jelly from the rest of the species is that its four horseshoe-shaped gonads are highly visible through the bell. These creatures typically grow to between twenty and thirty centimetres in length although some have been recorded at around forty centimetres. The lifespan of the jellyfish is typically between six months and one year.

The moon jellyfish is found across the world. They are a versatile creature and can survive in both tropical and freezing waters. They are typically inshore creatures and will often be found in harbours or estuaries. They prefer fairly consistent conditions as they rely on the current to move around.

A typical diet for this jellyfish will consist of plankton, small fish, small crustaceans, eggs, larvae and worms. Their prey is caught when it brushes against the tentacles of the jellyfish. Small amounts of toxin are released on contact, paralysing the prey and rendering it incapable of escape. The food is then transferred to the mouth of the jellyfish and into the stomach area where it is digested. Any waste products are expelled through the thin membrane that surrounds the body of the jellyfish. As well as being a predator the jellyfish is also prey to several species of large fish, such as the Sunfish, sea turtles, some marine birds and other jellyfish. They can also be attacked by parasites.

The reproductive cycle of the moon jellyfish is slightly different to that of other species. The breeding cycle normal runs from April through to September. The female will place the eggs into pits in the oral arms. They will then be released into the sea. The male releases sperm into the sea and this fertilizes the eggs. The eggs do not hatch into baby jellyfish, instead they become creatures called planula. After being carried by the current for some distance the planula sink to the bottom and find somewhere to attach whilst developing. Jellyfish reach sexual maturity in the spring or early summer. By the time late autumn/early winter arrives the jellyfish are exhausted by a combination of reproducing on a daily basis and lower food levels and generally start to die off.

There are very few reported cases of humans being stung by the moon jellyfish. The venom produced is not powerful enough to break through tough skin. It is really only used as a method of hunting against smaller prey that swim past and get caught or touch the tentacles. The other method that is used is a layer of mucus over the jellyfish that smaller prey will get stuck to and can't escape.

This species can swim if they need to. However, they generally prefer to float near to the surface of the water as they rely mainly on the currents and wind for motivation and for hunting. They will, more often than not, be found in large quantities in harbours and estuaries where the water is warmer and the currents are more stable. Also food is in fairly plentiful supply for them, especially during the spring and summer months.

This is one of a number of species that can be kept in captivity. Many are kept on public display in aquariums across the world. In fact, given the right level of care, attention and nutrition the moon jellyfish can successfully survive for several years in captivity, making them one of the more favoured and common species to be kept in such a manner.

For more information, pick up the Nook version of “Jellyfish As Pets“ at Barns and Noble.
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