How do Jellyfish communicate?

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Steve

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How do Jellyfish communicate?
« on: 06/09/2009 14:30:03 »
Steve asked the Naked Scientists:
   
Jellyfish swim in groups. How do they communicate to stay together?

What do you think?

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Offline LeeE

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How do Jellyfish communicate?
« Reply #1 on: 06/09/2009 16:52:27 »
Jellyfish can, but don't always swim in groups.

Any degree of communication between jellyfish is likely to be by chemical means: the jellyfish will be producing and releasing various compounds into the water that can probably be sensed by other jellyfish, so it's probable that jellyfish have some idea of whether there are other jellyfish nearby, but I doubt that there's any meaningful communication between them.  Neither do I think that they deliberately group together for mutual defense, as with flocking birds and schooling fish.  With birds and fish it is the speed of the individuals that make the flocking/schooling tactic effective, by making it difficult for a predator to identify a single specific target.  Jellyfish just aren't fast enough for this to work.

I would guess that large groupings of jellyfish occur either because they've all detected the same concentration of food or because they all hatched in common region and, all reacting in the same way to the same common stimulus, haven't drifted apart yet.  If all the jellyfish in a large concentration are similarly sized it suggests that they are all the same age and have grown up together.  Conversely, if they are different sizes and species it would suggest that they have come from different places but have all detected the same source of food.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline Don_1

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How do Jellyfish communicate?
« Reply #2 on: 07/09/2009 08:47:38 »
In addition to Lee's highly probable explanation, there is also the reproduction requirements. Jellyfish are both asexual and sexual reproducers. No mating takes place in sexual reproduction, the egg is fertilised by the sperm released into the sea. Proximity of the parents is therefore essential.
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Offline thedoc

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Monterino Bonjevalien

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« Reply #4 on: 24/03/2015 09:04:41 »
Helen... If jellyfish have eyes, how can they not have brains? Eyes are useless without a processor to interpret what they're seeing. Secondly, humans treading water in the ocean get separated rather easily. With our giant primate brain... There's something missing- they *must* willfully stay together.