Octopus Genome Reveals Sea Creature's Secrets

This month in Nature, an international team of researchers released some of their key findings after a first-of-its-kind study of the genome of the California two-spot octopus. The team found a massive and unusually arranged genome, with many genes unique to the octopus that could provide clues to the unusual animals.

One of the researchers, University of Chicago neurobiologist Cliff Ragsdale, joins Chicago Tonight to discuss the ongoing project.

Below, a summary of the report in Nature and more information about the California two-spot octopus. 


Octopus bimaculoides

The California two-spot octopus (Octopus bimaculoides) is a cephalopod, a class of predatory mollusks. Cephalopods—which include octopuses, squids, cuttlefish and nautiluses—are "characterized by a completely merged head and foot, with a ring and/or tentacles surrounding the head,” according to the University of Michigan Museum of Zoology’s online database the Animal Diversity Web.

The California two-spot octopus is typically light brown or mottled in color, with its namesake characteristic two spots under each eye. Scroll over the image below to learn more about the octopus.

The study

Octopuses, along with other cephalopods, possess unique adaptations, such as the ability to regenerate limbs, and a complex camouflage system. In order to study these traits, the California two-spot octopus’s genome was sequenced. Genome sequencing is determining the DNA sequence of an organism’s genome (its genetic material).

University of Chicago neurobiologist Cliff Ragsdale, one of the researchers says now that the genome is sequenced, scientists can study the octopus’s unique features – like it’s highly-developed brain and its famous arms. “Its arms are this fantastic prehensile sensory motor structure," he said. "They can reach into some place it can’t see, but it can taste, hmm, is there a crab there?”

In the study, the California two-spot octopus’s genome was sequenced, “to a high level of coverage—on average, each base pair was sequenced 60 times. To annotate the genome, the team generated transcriptome sequence data—which can be used to measure gene expression based on RNA levels—in 12 different tissues types,” according to an article on the study by the University of Chicago.

The findings

Researchers estimate the California two-spot octopus’s genome is 2.7 billion base-pairs (the human genome contains approximately 3 billion base-pairs).

“They identified more than 33,000 protein-coding genes, placing the octopus genome slightly smaller in size, but with more genes, than a human genome,” the University of Chicago article states.

Initially, researchers hypothesized the large size of the octopus genome was due to genome duplication events during evolution. But no evidence of genome duplication was found.

Instead it was discovered that “the evolution of the octopus genome was likely driven by the expansion of a few specific gene families, widespread genome shuffling and the appearance of novel genes.”

“This genome as compared with other invertebrate genomes looked like it was thrown in a blender,” Ragsdale said. “People always say aliens aren’t going to land and offer themselves up for experimental neuroscience, so the next best thing is cephalopods!”

 

  • A young Octopus bimaculoides peers out of her den. (Photo Credit: Caroline Albertin and Abigail Point)

    A young Octopus bimaculoides peers out of her den. (Photo Credit: Caroline Albertin and Abigail Point)

  • An Octopus bimaculoides clings to the wall of his aquarium using his sucker-lined arms and displays his blue eyespots. (Photo Credit: Caroline Albertin and Abigail Point)

    An Octopus bimaculoides clings to the wall of his aquarium using his sucker-lined arms and displays his blue eyespots. (Photo Credit: Caroline Albertin and Abigail Point)

  • An adult California two-spot octopus (Octopus bimaculoides) spreads out, displaying his namesake eyespots and exploring the floor of his aquarium and a Duplo with his flexible, sucker-lined arms. (Photo Credit: Caroline Albertin and Abigail Point)

    An adult California two-spot octopus (Octopus bimaculoides) spreads out, displaying his namesake eyespots and exploring the floor of his aquarium and a Duplo with his flexible, sucker-lined arms. (Photo Credit: Caroline Albertin and Abigail Point)

  • A juvenile California two-spot octopus (Octopus bimaculoides) explores her tank while displaying her namesake blue eyespot. (Photo Credit: Caroline Albertin and Abigail Point)

    A juvenile California two-spot octopus (Octopus bimaculoides) explores her tank while displaying her namesake blue eyespot. (Photo Credit: Caroline Albertin and Abigail Point)

  • A California two-spot octopus (Octopus bimaculoides) peers out of her den. (Photo Credit: Michael LaBarbera)

    A California two-spot octopus (Octopus bimaculoides) peers out of her den. (Photo Credit: Michael LaBarbera)

  • A juvenile California two-spot octopus (Octopus bimaculoides) holds onto the walls of her aquarium with her flexible, sucker-lined arms. (Photo Credit: Michael LaBarbera)

    A juvenile California two-spot octopus (Octopus bimaculoides) holds onto the walls of her aquarium with her flexible, sucker-lined arms. (Photo Credit: Michael LaBarbera)

  • A California two-spot octopus (Octopus bimaculoides) spies a nearby crab. (Photo Credit: Michael LaBarbera)

    A California two-spot octopus (Octopus bimaculoides) spies a nearby crab. (Photo Credit: Michael LaBarbera)

  • A California two-spot octopus (Octopus bimaculoides) extends a sucker-lined arm out of her den. (Photo Credit: Michael LaBarbera)

    A California two-spot octopus (Octopus bimaculoides) extends a sucker-lined arm out of her den. (Photo Credit: Michael LaBarbera)

  • A juvenile California two-spot octopus (Octopus bimaculoides) descending from his perch. (Photo Credit: Yen-Chyi Liu)

    A juvenile California two-spot octopus (Octopus bimaculoides) descending from his perch. (Photo Credit: Yen-Chyi Liu)

  • A juvenile California two-spot octopus (Octopus bimaculoides) displaying a blue eyespot reaches up with a long, sucker-lined arm. (Photo Credit: Yen-Chyi Liu)

    A juvenile California two-spot octopus (Octopus bimaculoides) displaying a blue eyespot reaches up with a long, sucker-lined arm. (Photo Credit: Yen-Chyi Liu)

  • (Photo Credit: Judit Pungor)

    (Photo Credit: Judit Pungor)

  • A California two-spot octopus (Octopus bimaculoides) displays its blue eyespot and its long, flexible, sucker-laden arms. (Photo Credit: Judit Pungor)

    A California two-spot octopus (Octopus bimaculoides) displays its blue eyespot and its long, flexible, sucker-laden arms. (Photo Credit: Judit Pungor)

 Find out how the octopus genome differs from some of its cousins, like oysters and clams in the video below.