h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

How could Sigmund Freud calm down an anxious jellyfish?

penis envy and he wanted to have sex with his mother

How could he tell the jellyfish was anxious in the first place

That's easy: in the case of the Polyorchis jelly which is the species I had in mind, they are visibly agitated when their bell palpitations increase and they retract their tentacles.

I don't know how Sigmund felt about his mother but that's not correct.

He cooled down the water?

Or he tampered in some other way the jellyfish's environment?

The temperature has nothing to with it.

But your right about the environment, I'm after a very specific action though.

he played it soothing music

He tapped some soothing words in Morse code onto its aquarium.

Jellyfish don't have ears or brains for that matter.

Did he give them more space? (i.e. a bigger tank or deeper water?)

A good thought but no, jellyfish frequently swarm so in so far as it is possible to judge these things it is reasonable to surmise that they don't mind each others company.

Possibly a klaxon, but is this colour therapy?

Go on...

Well, I'm guessing he lined the tank with different colours to test the jellyfish's reaction.

I've heard that green is fairly restful to humans, so was it that?

+3 for Icy.

Green light does relax the Polyorchis.

(I was looking for answer like: he replaced his light-bulb with a green one, so that's close enough.)

But can you work out why?

Something to do with the wavelength of green light? Does it stimulate the release of some hormone or other?

Because it corresponds with the colour of natural light filtered through their native waters to their preferred depth?

+3 Icy

+3 Robyn.

You're both right.

Their transparency, means that Jellyfish are sensitive and vulnerable to the particular wavelength of light which the Polyorchis jelly perceives by means of a series of light-sensitive cells that ring it's bell.

The Jellyfish ascend the water column at night, when there isn't much light around however as the sun rises they descend again and the prevailing theory is that they sense the increasing length of the light frequency s their trigger.

Light doesn't pass down through water to any great depth. However in shallower waters the light spectrum is split and reaches down some of the way. The shorter the wavelength the greater the energy so the more deadly to the jelly but also conversely the shallower the depth to which it penetrates.

Red light (620 - 750 nanometres)is one of the shortest and most energetic lights penetrates to a depth of about 15 metres. Yellow Light (570 - 590nm) can get down to about 50m.

Green and blue light can decend the deepest, the very bottom of the euphotic zone, beyond which photosysnthesis is imposible.

The Polyorchis inhabits harbours and bays typically, which are no deeper than 100 metres, so it's natural habit has a light frequency somehwere between green and blue.

This frequency of light is 'home' at it is how the jelly can distinguish it's height in the water column as it rises and descends with each day.

http://www.youtube.com/watch?v=HBG1t2iLccA (from 5 minutes onward)

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Why Sigmund Freud? Well why not?

Sources:
http://www.waterencyclopedia.com/La-Mi/Light-Transmission-in-the-Ocean.html
http://jellieszone.com/polyorchis.htm

That'll make up a little for my klaxon on the other thread...