Octopuses may evoke a variety of reactions in us — fascination, awe, and even fear — but boredom is certainly not one of them. The genome of this eight-armed marvel with camera-like eyes has recently been sequenced. It brings out some surprising revelations.
The importance of sequencing the octopus genome
The genome-sequencing project published in Nature 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 target animal for this initiative was the California two-spot octopus, or the Octopus bimaculoides. Both the genome and the multiple transcriptomes (products of the genome) were studied.
A member of the phylum Mollusca, which also houses other sea creatures like squid and cuttlefish, octopuses are blessed with unique behavioral and predatory characteristics. The objective of the study was to delineate the molecular basis for this superior intellectual ability.
The octopus has a bigger genome than most of its cousins
The size of the octopus genome is almost as big as that of a human, and much bigger than its relatives, like oysters or clams. Contrary to previous belief, this tremendous increase in size is not due to genome duplication, but due to expansion of a few specific gene families that were initially thought to be enlarged only in vertebrates. One such gene group is called the protocadherins, which supervises the development of neurons, and how they communicate with each other. The number of genes belonging to this family is more than twice that of mammals, which could explain the large size of the octopus brain and its strange anatomy. It also accounts for how octopuses can learn and remember complex tasks, like unscrewing a jar to prey on a crab stuck inside it.
We now know what makes octopuses change shape and color
The researchers found the expansion of another gene family called the zinc-finger transcription factors, hundreds of which were unique to the octopus, and were concentrated in its suckers, neural tissues and skin. These transcription factors play an important role in development, and are also thought to contribute to the camouflage and deception that are commonly seen in an octopus.
Along with the expansion of two major gene families, many other minor genes were identified that could have bestowed upon the octopus, its singular morphology and intelligence.
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