Rock pools

VulcanSpirit
Richard & Alison Brunstrom
Fri 17 Feb 2012 13:05
I had not realised how rare the British seashore rockpools are at global level. To get good tidepools there must be a large tidal range, the right geology and coastal morphology, and a temperate climate. We have seen nothing like them since leaving the UK, and there are certainly none here!
 
Instead there are reefs. Here I am at low tide (less than 1m range) walking out onto the reef. No pools just shallow water which is difficult to see into because of the constant wind at this time of year.
 
 
And here is the best thing I found.
 
 
This is the Caribbean Reef Octopus Octopus briareus; he is about 30cm across, perhaps a little larger if he stretched his legs out fullyHe was crawling along hunting in the shallow water - as you can see his eyes are above the surface so he was hunting by feel. It was a quite extraordinary sight to see him crawling quickly along actively searching in all directions with eight limbs at once, constantly changing colour quite dramatically, from totally white to dark brown and an infinite number of spotty and striped versions inbetween. Amazing.
 
You can just about see his eyes. Octopus eyes are strikingly similar in morpholgy to human eyes. They are 'camera type' with a lens, retina and pupil but have evolved completely separately from our eyes. In zoology they are used as a classic demonstration of 'convergent evolution' - starting from two very different positions the eyes of humans and octopuses have independently evolved to be very similar because they are performing the same function and evolutionary pressure has therefore driven their development in the same direction.
 
It is one of the great ironies of our time that the strangely resurgent creationists should use the structure of the eye to 'prove' (with no evidence other than their conviction) that because of its complexity it must have been created, complete, by God - while scientists use exactly the same complexity to prove (but this time with rock solid evidence) the fact of evolution. We now know, without doubt, that sight has evolved independently at least six times (presumably because of the enormous advantages it bestows), and use the similarity of the human and octopus eyes to demonstrate the power of evolutionary pressure to drive development. But sadly no amount of evidence is going to convince someone whoe mind is closed - and hence the current frightening nonsense of the religious right in the USA which is surfacing in the Presidential campaign. .