Scientists are one step closer to finding the genes responsible for the unusual biology of the octopus – including the cephalopod’s ability to change skin color – after successfully sequencing the genome of a type of the creature commonly found in California.
The genome sequencing effort, which will be detailed in the August 13 edition of the journal Nature, was led by scientists from the University of California, Berkeley, the Okinawa Institute of Science and Technology Graduate University (OIST), and the University of Chicago.
The researchers examined and annotated the genetic code of the common California two-spot octopus (Octopus bimaculoides), and found a series of significant differences between the DNA of this creature and the DNA of other invertebrates, they explained in a statement.
Project co-leader Dr. Daniel Rokhsar, a professor of molecular and cell biology at UC Berkeley, told redOrbit via email that he and his colleagues “found a family of related genes, called reflectins, that have been implicated in skin color change. These are found only in cephalopods. However, we don’t know how the changes in skin color are controlled.”
Genes for complex neural circuit, independent arm movement discovered
In addition, Dr. Rokshar said that his team also discovered “a large family of genes that, in vertebrates, are known to enable complex neural circuits to form. Invertebrates typically have only a few of these genes. Even though octopus and vertebrates (including humans) both have a great variety of such genes… the way that this gene diversity is set up in cephalopods is completely different from how vertebrates do it. This is an example of convergent evolution.”
Essentially, the genome research revealed that the nervous system of the octopus is organized in a completely different way than that of humans. Their central brain surrounds their esophagus, a feature commonly found in invertebrates, but it also has groups of neurons in its arms that allow them to move relatively independently and autonomously. Better understanding the way the brain of the octopus works with each of its eight arms could help engineers develop new flexible, prehensile arms for robots that could outperform jointed ones under water.
“The octopus genome makes studies of cephalopod traits much more tractable, and now represents an important point on the tree of life for comparative evolutionary studies,” co-author Clifton Ragsdale, associate professor in neurobiology, organismal biology, and anatomy at the University of Chicago, explained in a statement. “It is an incredible resource that opens up new questions that could not have been asked before about these remarkable animals.”
Dr. Rokshar added that the genome of the octopus was “in general… much larger and more scrambled than other invertebrate genomes that have been studied to date.” Among the unusual discoveries was the fact that the ‘hox’ or ‘homeotic’ genes (genes which control the body plan of an embryo along the anterior-posterior axis) of an octopus were “dispersed,” not “organized in a very well-controlled cluster” as in other genomes.
(Image credit: Thinkstock)
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