Figments of Reality by Ian Stewart Jack Cohen

Author:Ian Stewart, Jack Cohen
Language: eng
Format: mobi
Tags: Non-fiction, Popular science
Published: 2011-10-23T02:31:16+00:00

figments of realit y

pincer-like claws and is carnivorous; it regards anything less than half its size, which moves, as food, which it attacks, snipping or tearing off any appendages.

It then eats what’s left – which is often appendage rather than prey, and could be a piece of floating seaweed, or even a lump of wood or plastic in the hands of an experimental zoologist. When the third form metamorphoses into the (small) adult shape, taking up life in the coral crevices, it continues this rather indiscriminate butchery. At this stage, however, it never attacks tiny stones, pieces of coral, or seaweed. It has now learned to discriminate between prey, predators, and the ‘neutral environment’. Movement – especially movement that changes direction – is its cue for attack. You can see mantis shrimps doing this in an aquarium. If you present them with food held in a forceps, they will look very carefully at it, their eyes following it, and then they will attack. They will attack the forceps three or four times, as well, but after that they learn to take the food from it. If presented with an empty forceps they will eye it carefully, sometimes approach it, very rarely attack. But sometimes they will duck down into a crevice and then quickly come up again, as if they are ‘hoping’ that the forceps has now got some food in it ...

Surprisingly, little coral octopuses show just the same behaviour, learning to take food from forceps, and ‘hoping’ that empty forceps will fill with food if they turn their eyes away for a few moments. These similarities of behaviour in organisms whose brains are organised in totally different ways tells us that there ( a)

( b)

( c)

( d)

( e)

Figure 22 Life cycle of the mantis shrimp Squilla mantis. (a) Metanauplius. (b) Pre-zoea.

(c) Protozoea. (d) Antizoea. (e) Adult.

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