Scientists Sequence Octopus Genome for First Time

two-spot-octopus
The California two-spot octopus is the first of its kind to have its genome sequenced, which could have huge implications for understanding these intelligent animals. Michael LaBarbera

How do octopuses rapidly change color? How are they intelligent enough to recognize and remember people, twist open child-proof pill bottles, navigate mazes and engage in other acts that other invertebrates cannot?

There are many questions about octopuses and other cephalopods—a group of relatively intelligent mollusks that include squid and cuttlefish—that we don't know the answers to. But today, scientists have made an important step in addressing some of those queries: They've sequenced the first cephalopod genome, that of the California two-spot octopus. The results are published in the journal Nature.

The genome is quite different from any other ever seen, as one might imagine. One striking finding was the large number of genes involved in producing protocadherins, a protein that's vital for the development and function of the octopus nervous system, says study co-author Clifton Ragsdale, a researcher at the University of Chicago.

There are actually 2.5 times more of these genes in the octopus than in the human, adds co-author and graduate student Caroline Albertin.

The scientists also found a large number of genes coding to zinc-containing transcription factors, which help regulate how genetic material is turned into proteins. These are important for many bodily functions, including those of the brain. "These are genes thought to be important for humanness, they also appear to be important for octopus-ness," Ragsdale says.

Researchers found the genome to be much more jumbled than expected. Genes in a family called HOX 2, that control the animal's body plan, are usually found next to each other in other animals, but in this octopus, they are found scattered thither and yon about the gnome. This, along with an unusual number of repeated segments, made the sequencing difficult, says Jan Strugnell, a researcher at La Trobe University in Australia who wasn't involved in the study.

"The vast rearrangement and repetitive nature of the genome is very difficult to assemble," Strugnell says. "Therefore we have seen loads of other genomes—recently 48 species of bird—before we have seen any octopus genomes. The authors are to be commended on achieving this. Ultimately it will help us learn a lot more about how complicated and highly differentiated structures evolve—including well-developed brains and 'vertebrate-like' eyes."

Roger Hanlon, a senior scientist with the Marine Biological Laboratory at Woods Hole, Massachusetts, adds that the study will allow researchers to "bring cephalopod physiology, brain and behavior studies into the genomic era along with their sister species squids and cuttlefish.… This marks an exciting time in evolutionary, neural and behavioral sciences."