Campus graduate student, father uncover possible secret of octopus vision

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A UC Berkeley graduate student teamed up with his father on research, published Tuesday, that revealed for the first time a potential mechanism that allows octopuses and other cephalopods to see color.

Scientists have long questioned how octopuses only have one type of light receptor — resulting in black-and-white vision — yet are also capable of color-sensitive changes for camouflage and mating signals. The research, which began about a year ago, suggests that the unique, U-shaped pupil in cephalopods acts as a prism that allows for multi-chromatic vision.

“I think this is really clever research,” said Bruce Robison, senior scientist at the Monterey Bay Aquarium Research Institute. “I suspect they’re right, and it’ll be interesting to see if someone can test their hypothesis, their idea.”

Alexander Stubbs, lead researcher and campus graduate student, worked with his father Christopher Stubbs, an astrophysics professor at Harvard who mainly worked on the computational model for the physics of the experiment. The study was funded by the UC Berkeley Museum of Vertebrate Zoology, Harvard University and the Natural Science Foundation.

“How could I pass up an opportunity to do a cool science project with my son?” said Christopher Stubbs, adding that the research had nothing to do with his field of study. “But having said that, I’m a scientist too, and solving interesting projects is what we all do.”

Alexander Stubbs hopes his paper will encourage other people to do behavioral experiments in order to further validate the study. The research has additional implications on animals, such as dolphins and spiders, and technological applications for a possible low-light camera system.

The research was based on the unique pupil structure of cephalopods which causes chromatic aberration — an effect that prevents the eye from being able to focus and increases blurriness of color. The research suggests that cephalopods use chromatic aberration to recognize colors based on clarity because different colors have different levels of blurriness.

Other experts in the field, however, have expressed skepticism on whether the research can indeed prove that cephalopods have color vision. According to Thomas Cronin, a biology professor at University of Maryland, Baltimore County, other animals use chromatic aberration to judge distance and not color.

Cronin said the purpose behind the flashes of color released as part of the mating signal could be meant to attract other cephalopods through a change in pattern rather than a change in color. He added that camouflage could be caused by blending to muddy colors commonly found in the ocean, rather than color-sensitive changes.

Alexander Stubbs stood by his research, however, saying that cephalopods have two eyes and therefore already have an accurate judgement of distance without chromatic aberration. He added that the pupil shape was actually a detriment that blurred a cephalopod’s vision — a possible trade-off in order to see color.

Alexander Stubbs said he plans on continuing his research into color vision and is working on a dissertation on the evolution of color vision in lizards and cephalopods.

Contact Lillian Dong at [email protected].