Day octopus

Octopus cyanea

Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Family: Octopodidae
Genus: Octopus
Species: Octopus cyanea

The day octopus, also called the big blue octopus or cyanea octopus, is one of the few octopuses that does most of its hunting in daylight. Adults reach a mantle length of around 16 cm with arms up to about 80 cm, and they are masters of disguise, shifting in seconds from mottled brown to pale cream, deep red, or nearly black while raising skin papillae to match the reef. A dark false eyespot sometimes shows at the base of the arms.

It lives on shallow coral and rubble reefs throughout the Indo-Pacific, including across the Philippines, usually from the shallows down to about 25 m. Divers most often find it moving boldly between dens, probing holes with its arms for crabs, shrimps and small fish, or sitting in a den entrance ringed with discarded shells. Groupers, goatfish and wrasses often follow it closely, hoping to snatch prey it flushes out.

Recent genetic work suggests this species does not belong in the true Octopus vulgaris group and is closer to the genus Abdopus, so its genus is currently unresolved and the name Octopus cyanea is kept for now. Like most octopuses it lives only about a year, and females guard their eggs in a den until they hatch, dying soon afterwards.