A distinct striped pattern on a dwarf octopus species varies from individual to individual, which could help researchers monitor the rare animal.
Pygmy zebra octopuses (octopus chierchiae), also known as the less specific striped octopuses, live in the shallow waters of the Pacific coast of the Americas and are crossed by alternating brown and white stripes.
Feeling that little is known about the animal or how it interacts with its environment, Benjamin Liu and his colleagues at the University of California, Berkeley bred two adult males and two adult females in their lab.
The team then individually housed 25 octopus hatchlings, which they photographed and filmed once a week for about 2 years.
When the octopus was about two weeks old, its patterns became visible to the naked eye and were fully visible after four weeks. Pygmy zebra octopuses frequently change their appearance to mimic their surroundings, in response to disturbance, so researchers focused only on patterns that persisted for hours or days.
They discovered that each of the 25 octopuses had a unique pattern of stripes.
Volunteers who were shown photographs of octopuses could even identify whether the photographs were of the same octopus or two different octopuses, with an average accuracy of 84.2%.
This suggests that individual pygmy zebra octopuses could be repeatedly identified and monitored in the wild over time, which could aid their conservation, the researchers wrote in their paper. These octopuses are rare and delicate, so ideally should be studied in a way that doesn’t take them away from their natural environment, they wrote.
Although the stripes on zebra pygmy octopuses seem to vary from individual to individual, it is unclear why they have these stripes. “The fact that they can turn stripes on and off and even do so unilaterally suggests to me that they are used in communication or at least to make signals more obvious,” says study author Roy Caldwell.