by
bloglikesit
@ 13/02/2008 - 13:02:07
Being fairly skint lately, we’ve been watching a lot of TV. We have a schedule.
Tuesday consists of Eastenders on BBC1, followed by Natureshock on 5, then Prison Break on RTE2 (an Irish channel), and finally Medicine Men Go Wild on 4+1 (perhaps with a little Family Guy on BBC3 before bed).
Natureshock has been a pretty good series. They take a stange occurrence in the animal kingdom and treat it like a CSI sort of thing. The first one we saw was a strange corpse that had been found in the Everglades. It was revealed to be two corpses – a massive snake and an alligator. But had the snake killed the alligator or had the alligator killed the snake? Well, a bit of both, obviously. The snake (a Burmese python, probably an ex-pet released into the wild when it got too big) had killed and eaten the alligator, which was too big and had burst out of the snake’s belly, killing it. Simple, really.
Over the weeks, we’ve seen bear cannibalism, 'zombie' crocodiles and last night jellyfish swarms.
Last night's programme was amazing. Not so much of a CSI style murder investigation as the others have been, but more an analysis of what’s going on with jellyfish.
The really interesting bits included the fact that scientists have recently discovered that jellyfish (certainly box Jellyfish anyway, not sure about other types) have eyes! Looking at them, they look totally transparent and you’d think they were eyeless – as everyone did until last year. Each corner of a box jellyfish has six eyes! That’s 24 in total! Only eight of them are sophisticated, the others only sense light and shadow, but the other eight are actually quite complicated and see very well, better than many fish, even compensating for refraction from objects above the water, enabling them to navigate using landmarks when close to shore!
Not only that, but they also have four brains, one in each corner, and they each work their own set of eyes. They compete with each other for control of the body depending on what they see. The one nearest the fish wins the fight! They actively hunt, they don't just wait for something to come near.
They showed an experiment with a box jellyfish in a tank. They put two white poles in the tank, and the jellyfish bumped into them and knocked them over. They put black poles in, and it navigated happily around them. So they can't see white very well, but black is no problem.
Then they put red poles in, and the behaviour totally changed. It kept as far away as it could, right in the corner of the tank. This research has led to changes like making nets around beaches red to deter jellyfish from even coming near them.
Fascinating stuff. They showed the jellyfish lifecycle too. The fertilised eggs drop to the sea bed and become little 'polyps' stuck to rocks and things, feeding on plankton that passes by. They can stay like that for years, and then suddenly they change – nobody knows exactly what causes it – and the polyp clones itself again and again, and the clones floats away. The clones develop into new jellyfish! The polyps end up looking like a little stack of jellyfish before they float off, one by one.
The Japanese government tried to control a swarm of massive 2m wide jellyfish off their coast by sending out boats with nets made of sharpened steel wire, which they dragged through the swarm to cut the jellyfish into pieces.
Somehow the surviving jellyfish knew what had happened, and compensated by going into a breeding overdrive – each producing millions of eggs! Many times more than they normally produce.
There was loads more in the programme, such as the absolutely tiny jellyfish that you can't see in daylight that can kill you, but I think I've probably bored you enough now. If you happen to see it repeated, it's well worth a look.
EDIT:
It's definitely only box jellyfish that have the sophisticated eyes, and it was 2005 when the research was done, not last year. So there.