Amphioctopus marginatus

The coconut octopus, or veined octopus, is a medium-sized cephalopod living in the tropical waters of the western Pacific and Indian Oceans. It favors sandy seafloors where shells or debris are plentiful. Its diet mainly consists of shrimp, crabs, and clams. This species is one of only two octopuses known to walk on two arms, and it is also recognized for gathering and using tools—such as coconut halves and seashells—as portable shelters.

Classified under the family Octopodidae, the species was first described in 1964 by Japanese malacologist Iwao Taki, who named it *Octopus marginatus*. The name *marginatus* (meaning “margined”) refers to the pale border around its eyes. It was later moved to the genus *Amphioctopus*. A 1976 description by Dong Zhengzhi, *Octopus striolatus*, is not considered taxonomically valid.

The octopus’s main body typically measures 5 to 10 centimeters long, and with arms extended it can reach about 30 centimeters. It can weigh up to 400 grams. Its usual coloring features dark, branching lines that resemble veins; the arms are dark with contrasting pale suckers, and a lighter triangular patch often appears just below the eye. In 2017, the complete mitochondrial genome was sequenced, revealing a close relationship with *Amphioctopus aegina*.

This species preys mostly on crustaceans like *Calappa* crabs and on bivalves. Females lay clutches of about 100,000 eggs, each 3 millimeters long, woven into long chains. The eggs are deposited inside a shelter—such as a coconut shell—where the female guards them until they hatch; like most octopuses, she starves to death during brooding. Eggs take 15 to 17 days to hatch, and the paralarvae are planktonic.

In March 2005, researchers from the University of California, Berkeley, reported in *Science* that *A. marginatus* can walk bipedally, a behavior they called “stilt-walking.” The octopus rolls two arms to move while using the other six to disguise itself, possibly to mimic a rolling coconut. This was first observed off Sulawesi, Indonesia, where coconut shells are common. Dr. Crissy Huffard noted that octopuses are the only animals without a rigid skeleton that can walk on two limbs. *A. marginatus* and *Abdopus aculeatus* are the only two octopus species known to do this. The species also crawls in the typical octopus fashion.