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returning to cephalopods

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A while back I wrote about the extraordinary spawning grounds of the Giant Australian Cuttlefish in Spencer Gulf, not so far from here. Though I’d heard of this habitat a while ago, courtesy of the controversy around the placement of a desalination plant nearby, it took a fascinating TV doco to really spur my interest. Another recent documentary on the intelligence of octopuses, together with some bad news about those spawning grounds, has prompted me to return to the subject of this fascinating class of molluscs.

I’m particularly interested in the sub-class of cephalopods which includes cuttlefish, squid and octopuses [fisherfolk cluster them together as inkfish, for obvious reasons], a sub-class which, it seems to me, has become flavour of the month, or year, or decade, for marine biologists of late.

This season, the numbers of cuttlefish coming in to breed and spawn at Point Lowly in Spencer Gulf have been disastrously low. Those that have come are generally smaller than usual. They normally congregate in mid to late June. No clear cut reason for this drop is on offer [the desal plant is still at the proposal stage – maybe they heard about it on the seagrape vine?], and we’ll have to wait and see if they return next year. Of course we also don’t know if they’ve relocated, or if this would be a normal thing to do – for example we don’t know for how long they’ve been breeding at Point Lowly. It appears that nobody is responsible for monitoring cuttlefish numbers, and presumably nobody is responsible for monitoring temperature, salinity and other variables there either.  The comments on the news article linked to above present various conspiracy theories, not too seriously I hope. BHP did it, to get rid of the cuttlefish as an environmental issue. The Greens did it, to highlight the sensitivity of cuttlefish to even rumours of environmental degradation. Others are arguing that the environment there has already been massively degraded recently, but they offer no suggestions as to what caused this, if it’s true. Hopefully some serious investigations can be made.

Meanwhile, research continues into the intelligence and learning abilities of octopuses. The documentary ‘Aliens of the Deep Sea’, which I saw a couple of nights ago, provided exciting proof of these abilities in a few simple but effective experiments. The most exciting of these involved a newly captured octopus being placed in a tank, where it tended to hide in a corner behind some rocks. A transparent container containing a crab, and with a hole on one side just large enough for the octopus to enter [octopuses are able to squeeze through the narrowest of openings, through distortions of their invertebrate bodies] was placed inside the tank. The octopus didn’t respond to the unfamiliar container. Then another tank was placed alongside it, containing an octopus of the same species. This octopus had been in captivity for some time, and had learned or been taught how to enter the opening to get at the tasty crab. So the experiment was repeated with the experienced octopus, and the inexperienced octopus literally rushed to the edge of its tank to get a ringside view of how the experienced octopus did it. I don’t know if there was any tricksy editing in this scene, but I do know that the sight of this eager spectating had me almost falling off the edge of my seat. And sure enough, when the experiment with the crab was repeated with the inexperienced octopus, it got the idea straight away, and was able to find the hole and get at the crab in no time at all. A number of similar experiments were shown [including the opening of a screw cap], and it became clear that the learning capabilities of these creatures were truly outstanding. It doesn’t seem to matter which species are chosen for these experiments, so it seems evident that such intelligence exists over the range of octopus species [there are presently around 300 recognized species], though more research might have to be done to confirm this.

All this raises tantalizing questions. How do they learn? Octopuses have short lifetimes [some as little as six months] and they learn virtually nothing from their parents, with whom they have almost no contact [females live only long enough to see their eggs hatch, and males die shortly after mating]. Also, how long have they been behaving in such an ‘evolved’ way? Cephalopoda date back some 500 million years, and a rare example of a fossilized octopus has been found, dating back 95 million years. This fossil appears to be remarkably similar to modern species – it appears that little evolving has taken place in the interim. So this kind of cleverness existed on the planet long before homo sapiens arrived on the scene. Indeed the first primates appeared only about 60 million years ago, according to current evidence. What we have here is a fascinating example of how highly intelligent life forms can evolve along completely different pathways from ourselves. Some researchers and atheists are keen to find extra-terrestrial life, especially of a highly evolved type, to demolish any notion that we are special, the uniquely privileged end-game of a supernatural designer. Yet we don’t have to look elsewhere for intelligence, it has been right under our noses throughout the lifetime of our species. We’ve just been too blind, too arrogantly bound up in our ‘specialness’, to really notice.

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Written by stewart henderson

August 30, 2011 at 1:02 pm

Posted in other life

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