Lifestyles for Better Living



Upsidedown Jellyfish


The upside down jellyfish, scientific name Cassiopeia xamachana, could very easily be mistaken for being something other than a jellyfish. They spend most of their lives lying on their backs, on the bottom of shallow waters and look very much like sea anemones or marine flowers. They much prefer warmer climates and will often be found on mud flats and amongst sea grasses or mangrove swamps.

There are two main reasons why these jellyfish lie on their backs. The first reason is as a defence mechanism against predators. The second, and probably the most important reason are feeding. There are types of algae that live inside the jellyfish. The algae need sunlight in order to feed; when they have taken what they require the excess food is passed on to the jellyfish. This process is known as photosynthesis and could not be performed if the jellyfish resided in deeper waters. As well as feeding this way the upside down jellyfish also uses its position to catch any small prey that may be passing above it. Their prey includes plankton and small fish and as with most species of jellyfish, will capture their prey by paralysing it rather than injecting it, as some species do. The food is then passed down to four pairs of elaborate mouth arms which break the food up. Once the food is broken up it then gets passed on to the secondary mouths and into the belly of the jellyfish for digestion.

These jellyfish come in a fairly wide variety of colours, from white, to pink, blue, green and brown. The most common ones are green; the colour of these jellies is determined primarily by the type and number of algae residing inside it. They are not the largest of jellyfish, reaching a maximum size of around fourteen inches. Their venom is not powerful enough to harm a human being, being just enough to create a very itchy rash at the worst.

The breeding season for the Upside down jellyfish starts in the summer, as opposed to the winter months for most other species. They are another species, like the Sea nettle, that reproduces in 2 ways. Firstly the male injects sperm into the water. The female will then take the sperm into her body and pump it around to fertilise the eggs. These are then hatched into larvae which are pushed out into the water to make their own way. The second part of the reproductive cycle then starts. This is the asexual cycle. The larvae will make their way through the water, drifting on currents until they find a suitable place to settle. Once a specific area is chosen the larvae will settle on the bottom and attaché on to a hard flat surface. More often than not it is the leaves of the red mangrove tree that are chosen for this purpose.

Then the reproduction begins. Buds will form on the polyp, as these larvae are now known. The polyp then produces a carbon copy of itself on this bud which, when fully formed, is released into the sea. For a while this young upside down jellyfish are free floating, drifting through the water and feeding as they go. Once they reach around 2 cm in size they will drift to the bottom, turn upside down and there they will stay for most of the rest of their lives. Generally, unless they choose to move on, the only way one of these will move is if a crab picks it up and carries it along. The crab does this as a defence mechanism, using the jellyfish to ward off attack from its predators.

The Upside down jellyfish, Cassiopeia xamachana, can be kept in captivity but they are not the easiest species. A specific setup is required along with the correct nutrition and this should really only be attempted by an expert rather than a hobbyist.


For more information, pick up the Nook version of “Jellyfish As Pets“ at Barns and Noble.
You can also buy the PDF file from Paypal for $2.99

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