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LatestPhoto
A Box Jellyfish.
Photo: Courtesy of the Museum and Art Gallery of the Northern Territory

November 20, 2001
Box Jellyfish
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Log Transcript

Genevieve Johnson

This is Genevieve Johnson speaking to you from the Odyssey. Darwin feels like one of the hottest places on the planet. During the wet season, temperatures and humidity soar. You would assume that being a city on the ocean, locals would flock to the beaches. However, this is not the case as just offshore, the waters are teeming with the most toxic animal on the planet, the Box Jellyfish. Yesterday, we spoke with Phil Alderslade, a curator at the Museum and Art Gallery of the Northern Territory.

Dr. Phil Alderslade:

It's reckoned that they are probably and potentially the most deadly animals known to science. In fact, it is the only animal that can kill you in two to three minutes. With a snake, the venom may kill you in a half-hour and hour of something like that. The one that we get here, Chironex Fleckeri, is the main one we are talking about which can kill people. The population in Queensland consists of larger individuals. They can grow up to about 'so big' (hand movement). One can fill a 10-20 gallon bucket. Up here in Darwin, we don't get them larger than 10-11 centimeters across, about the size of a grapefruit.

It occurs in Northern Australia, from about the Tropic of Capricorn on the East Side across the top of Australia, to the Tropic on the West Side. It lives close to the shore. It loves muddy harbors, muddy bays, and sandy shores. It likes mangroves because there is lots of food there as well. So the best place to see it is in the shallow areas just off the beach. You can walk along the beach at high tide, the water is nice and calm first thing in the morning. You can get them in just 'knee-depth' water.

They are a fast moving jellyfish. Your average jellyfish that you imagine are like an upturned bulb or something, and tends to pump a little bit while it drifts around with the tides or the wind or whatever. Box Jellyfish gets on its side, the tentacles stream out behind it. It just goes where it wants. It has got 4 primitive eyes, one on each side. It can actually see something, we are not quite sure what, but it can pick out light and dark. It has got a primitive retina and primitive lenses in those eyes. It can certainly make some images. If you approach one in the water, it will see you. If you cast a shadow over it, it will see you and immediately turn for the bottom straight away. So for a jellyfish they are pretty 'cluey' animals.

LatestPhoto
Dr. Phil Alderslade, Curator Cnidaria at the Museum and Art Gallery of the Northern Territory in Darwin.
Photo: Chris Johnson

The top of bell of the animal, has got no stinging cells on it (stinging cells are a common term). In the tentacles, they have stinging cells called nematocysts. These are an amazing biological engineering mechanism. They are essentially a small capsule. We are talking about 1,000 of these on a head of a pin. They are that small.

When the tentacle brushes up against something, the animal has to work out if it is 'itself', the sand, a rock, another jellyfish, or some food. But they catch fish, by stinging the fish with the tentacles (or they catch prawns and fish) and the tentacle being able to stretch and are quite strong, acts like a fishing line. They can 'play' the fish with its tentacle. So the tentacles can stretch so it doesn't break. This is probably one of the reasons why it has the ability to stretch. And then the fish dies very quickly when it's paralyzed. Then it withdraws its tentacles up short turn upside-down. They can allow the fish or the prawn to settle inside the stomach cavity. They can close the stomach cavity and they can allow the stinging cells to be released from the tentacle. They stay stuck in the prey. They can give a bit of a puff, and the tentacles just waft out again and they keep the prey in there and digest it.

Log by Genevieve Johnson

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