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Four-armed jellyfish found

February 9, 2004 By Helen R. Pilcher This article courtesy of Nature News.

Bumpy sea creature is new species.

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Images of Stellamedusa ventana

Researchers have discovered a new species of jellyfish so different from its fellow creatures that it merits a new subfamily. The diaphanous beast, which dwells in deep waters off California, has a bell-shaped body and four fleshy arms.

The creature was first nicknamed 'Bumpy' by the researchers who found it, because it is covered in tiny bumps. But it now has an official moniker: Stellamedusa ventana.

'Stella' refers both to its translucent blue-white colour and its trailing arms, which make it look like a shooting star, while 'medusa' is a commonly used name for jellyfish. It is named 'ventana' after the robotic submarine that first caught Bumpy on video, explains its discoverer, Kevin Raskoff of the Monterey Bay Aquarium Research Institute in California.

The creature is unusual because it has arms instead of tentacles, says Raskoff. The arms protrude from inside the bell of the jellyfish and act like a pair of extended lips, helping guide food to the mouth. The bumps are clusters of stinging cells that help it capture prey.

The jellyfish's anatomy and behaviour are different enough to make it qualify as a new subfamily. "This is a pretty big deal," says Raskoff. For comparison, lions and domestic cats belong to the same family, but different subfamilies. This is a jellyfish equivalent, he says. The subfamily has been named Stellamedusinae, and brings the total number of jellyfish subfamilies to eight.

Jelly fishing

Raskoff and colleague George Matsumoto waited for years after first spotting the creature to publish their discovery because they wanted to collect more information about it.

Since its first sighting 13 years ago, this elusive jellyfish has been spotted only seven times - five times in California's Monterey Bay and twice in the Gulf of California, some several thousand kilometres away. Scientists have little idea where else it might be found.

It is thought to live at depths of 150 to 550 metres, just below the reach of sunlight. This dark realm of the ocean is home to many different types of jellyfish and other gelatinous creatures.

"It must be pretty rare," says jellyfish expert Claudia Mills of the Friday Harbor Laboratories at the University of Washington. Either that, or people just haven't noticed them. Jellyfish are often caught in fishing nets, but are diced into pieces by the webbing, makes them difficult to identify, she says.

During one dive, Raskoff and Matsumoto captured a specimen and brought it back to the lab, where they fed it shrimp and pieces of squid. The food drifted against the jellyfish and became stuck to its bumps. It was then transferred to the arms and moved into the waiting mouth.

The bumps probably eject poison in the prey to kill it, speculates marine biologist David Conway at the Marine Biological Association of the United Kingdom. Raskoff suspects that the creature, which is relatively large at 10 centimetres across and 20 centimetres long, may feed on fairly big prey such as other jellyfish and similar creatures.

References

  1. Raskoff, K. A. & Matsumoto, G. I. Stellamedusa ventana, a new mesopelagic scyphomedusae from the eastern Pacific representing a new subfamily, the Stellamedusinae. Journal of the Marine Biological Association of the United Kingdom, 84, 37 - 42, (2004).

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