With its eight prehensile arms lined with suckers, camera-like eyes, elaborate repertoire of camouflage tricks and spooky intelligence, the octopus is like no other creature on Earth.
Added to those distinctions is an unusually large genome, described in Nature on 12 August, that helps to explain how a mere mollusc evolved into an otherworldly being.
“It’s the first sequenced genome from something like an alien,” jokes neurobiologist Clifton Ragsdale of the University of Chicago in Illinois, who co-led the genetic analysis of the California two-spot octopus (Octopus bimaculoides).
The work was carried out by researchers from the University of Chicago, the University of California, Berkeley, the University of Heidelberg in Germany and the Okinawa Institute of Science and Technology in Japan. The scientists also investigated gene expression in twelve different types of octopus tissue.
“It’s important for us to know the genome, because it gives us insights into how the sophisticated cognitive skills of octopuses evolved,” says neurobiologist Benny Hochner at the Hebrew University of Jerusalem in Israel, who has studied octopus neurophysiology for 20 years. Researchers want to understand how the cephalopods, a class of free-floating molluscs, produced a creature that is clever enough to navigate highly complex mazes and open jars filled with tasty crabs.
The work was carried out by researchers from the University of Chicago, the University of California, Berkeley, the University of Heidelberg in Germany and the Okinawa Institute of Science and Technology in Japan. The scientists also investigated gene expression in twelve different types of octopus tissue.
“It’s important for us to know the genome, because it gives us insights into how the sophisticated cognitive skills of octopuses evolved,” says neurobiologist Benny Hochner at the Hebrew University of Jerusalem in Israel, who has studied octopus neurophysiology for 20 years. Researchers want to understand how the cephalopods, a class of free-floating molluscs, produced a creature that is clever enough to navigate highly complex mazes and open jars filled with tasty crabs.
The analysis also turned up hundreds of other genes that are specific to the octopus and highly expressed in particular tissues. The suckers, for example, express a curious set of genes that are similar to those that encode receptors for the neurotransmitter acetylcholine. The genes seem to enable the octopus’s remarkable ability to taste with its suckers.
Scientists identified six genes for proteins called reflectins, which are expressed in an octopus's skin. These alter the way light reflects from the octopus, giving the appearance of a different colour — one of several ways that an octopus can disguise itself, along with changing its texture, pattern or brightness.
Another discovery hinted at the basis of an octopus’s intelligence. The genome contains systems that can allow tissues to rapidly modify proteins to change their function. Electrophysiologists had predicted that this could explain how octopuses adapt their neural-network properties to enable such extraordinary learning and memory capabilities.
The octopus’s position in the Mollusca phylum illustrates evolution at its most spectacular, Hochner says. “Very simple molluscs like the clam — they just sit in the mud, filtering food. And then we have the magnificent octopus, which left its shell and developed the most-elaborate behaviours in water.”
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