They have waited, largely forgotten, beneath the waves while humans plundered fish populations and caused the oceans to warm.
Now, scientists believe, the time of the tentacled ones may have arrived.
Around the world, experts have catalogued a significant increase in numbers of cephalopods — which include octopuses, squid, and cuttlefish — over the past six decades.
As populations of many fish species fall, the multi-limbed creatures, the biggest, most intelligent and mobile molluscs on the planet, appear to be flourishing.
Zoe Doubleday, from Australia’s Environment Institute at the University of Adelaide, said: “Our analyses showed that cephalopod abundance has increased since the 1950s, a result that was remarkably consistent across three distinct groups.
“Cephalopods are notoriously variable, and population abundance can fluctuate wildly, both within and among species.
"The fact that we observed consistent, long-term increases in three diverse groups of cephalopods, which inhabit everything from rock pools to open oceans, is remarkable.”
The ‘brainy’ invertebrates have evolved some extraordinary adaptive traits, including suckered tentacles, camera-like eyes, colour-changing skin and complex learning behaviour.
One group of scientists who mapped the octopus genetic code said the animal was so strange it could be viewed as an ‘alien’ from another world.
Cephalopods may be able to cope with changing environmental conditions, such as rising temperature, better than many other marine species, said Dr Doubleday.
Overfishing may have also contributed to their success, the researchers believe.
The study, published in the journal Current Biology, was prompted by concern over declining numbers of the Giant Australian Cuttlefish at its chief breeding ground in South Australia’s Spencer Gulf.
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