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New species of jellyfish discovered with gonads on its head

11/05/2010 16:30:05
au/jellyfish_gonads_csiro

A new family of jellyfish discovered off Tasmania. Credit CSIRO.

Many new species of jellyfish discovered in Australia
May 2010. A spectacular new jellyfish has recently been found, ironically off the jetty of a wharf belonging to Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO), in Hobart, Tasmania. The new jellyfish has been given the name Csiromedusa medeopolis, and actually represents not only a new species but also a new family.

The jellyfish was discovered by researchers from the Queen Victoria Museum and Gallery in Launceston and the South Australian Museum. They used a specially-designed plankton net to catch the jellyfish off the CSIRO wharf. When they pulled up the net and looked at what they had caught under a microscope they found an amazing and unique jellyfish that had never been seen before.

"There it was, just waiting to be discovered," said jellyfish researcher Lisa-Ann Gershwin.

Tiny jellyfish, just 1-2mm long with gonads on its head
What they saw was a small 1-2 mm jellyfish, shaped like a flying saucer with a hole in the top of its head with its gonads (reproductive organs such as testicles and ovaries) sticking out, looking like tiny skyscrapers. Hence its name, csiromedusa meaning 'jellyfish from CSIRO' andmedeopolis meaning ‘city of gonads'.

New family of jellyfish
Well timed in the international year of biodiversity, the discovery of a new family is rare. "A discovery of a whole new family like this is an uncommon occurrence," said Lisa-Ann.

Many new species of jellyfish found
The researchers took samples from marinas, wharfs, jetties and boat ramps around Tasmania. Many new species of jellyfish were found in these samples but this jellyfish stood out from the crowd because it had a structure that was completely without parallel in the whole jellyfish world.

It belongs to the narcomedusa group of jellyfish that are found in deep water. Most jellyfish have two stages in their life cycle. They start as polyps - small cylinders that can either be free-floating or attached to the ocean floor, rocks or small clumps of algae. These polyps have tiny tentacles at the top to catch food.

From the polyp stage comes the jellyfish, or medusa, that drifts away in the ocean currents. The mature jellyfish then release sperm and eggs into the water, and these are fertilized outside the jellyfish in most species. More research is needed, however, to find out if Csiromedusa medeopolishas a similar life cycle as little is known about this new discovery.

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