Amphioctopus marginatus
Conservation status
Least Concern (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Order:	Octopoda
Family:	Octopodidae
Genus:	Amphioctopus
Species:	A. marginatus
Binomial name
Amphioctopus marginatus (Iw. Taki, 1964)
Synonyms
Octopus marginatus Taki, 1964 Octopus striolatus Dong, 1976 veined octopus coconut octopus

Amphioctopus marginatus, also known as the coconut octopus and veined octopus, is a medium-sized cephalopod belonging to the genus Amphioctopus. It is found in tropical waters of the western Pacific Ocean. It commonly preys upon shrimp, crabs, and clams, and displays unusual behavior including bipedal and quadrupedal walking as well as tool use (gathering coconut shells and seashells and using these for shelter).

Taxonomy

Amphioctopus marginatus is a species of octopus located in the family Octopodidae, genus Amphioctopus. The species was first described in 1964 by Japanese malacologist Iwao Taki as Octopus marginatus, and synonymously as Amphioctopus marginatus. In 1976, Z. Dong named the species Octopus striolatus but this name was not recognized as taxonomically valid.^[2][3]

Size and description

The main body of the octopus is normally 8 centimeters (3 in) long and including the arms, approximately 15 centimeters (6 in) long. The octopus displays a typical color pattern with dark ramified lines similar to veins, usually with a yellow siphon. The arms are usually dark in color, with contrasting white suckers. In many color displays, a lighter trapezoidal area can be seen immediately below the eye.

Behavior and habits

In March 2005, researchers at the University of California, Berkeley, published an article in Science in which A. marginatus was reported to show bipedal locomotion. It is one of only two octopus species known to display such behavior, the other species being Abdopus aculeatus. The authors discovered this behavior in an area off Sulawesi, Indonesia, where the sandy bottom was littered with coconut shells.^[4] The bipedal motion appears to mimic a floating coconut.^[5]

Researchers from the Melbourne Museum in Australia claimed the coconut octopus uses tools for concealment and defense by gathering available debris to create a defensive fortress. This behavior was observed in individuals in Bali and North Sulawesi in Indonesia.^[6][7][8] The researchers filmed the octopus collecting coconut half-shells from the sea floor that had been discarded by humans. They were then carried up to 20 meters (66 ft) and arranged around the body of the octopus to form a spherical hiding place similar to a clam-shell.^[7][9]

The species preys predominately on Calappa crabs and bivalves. Eggs are laid in clutches of 100,000 and are 3 millimetres (0.12 in) in length.^[2]

Distribution

The coconut octopus is broadly endemic to neritic, tropical waters in the Indian Ocean, Red Sea, Northwest and Western Pacific Ocean, and Southeast Asian Sea. Amphioctopus marginatus is listed as Least Concern on the ICUN's Red List. While the species may be threatened by fishing, it's wide distribution is seen as enough to compensate against human impacts.^[2]

Habitat

The species prefers shallow, subtidal waters along the continental shelf. The species has a maximum depth of 190 metres (620 ft), and can often be found in mud and sand substrates.^[2]