---
title: Big Blue Octopus (Octopus cyanea)
scientific_name: Octopus cyanea
common_name: Big Blue Octopus
taxon: Cephalopods
conservation_status: LC - Least Concern
published: 2023-12-26T16:23:19.806Z
updated: 2026-08-23T20:49:02.922Z
tags: Big Blue Octopus, Octopus cyanea, Cephalopods, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/molluscs/cephalopods/big-blue-octopus
---

# Big Blue Octopus (*Octopus cyanea*)

## Quick facts

- **Group:** Cephalopods (*Cephalopoda*)
- **Size:** 22 cm (80 cm)
- **Weight:** 6 Kg
- **Depth:** 1-150 m
- **Diet:** Carnivore
- **Activity:** Diurnal
- **Rarity:** Common
- **Habitat:** Coral reef and rubble, in a den marked by a midden of empty shells
- **Reproduction:** Egg layer, Gonochoric, Semelparous
- **Conservation status:** LC - Least Concern

## How to recognise it

- a midden of empty crab and shell fragments outside a hole in the coral
- skin that changes color and texture in front of you, including raised spikes
- arms spread into a web and dropped over a coral head while hunting
- mantle to 22 cm, arms to 80 cm

The common daytime octopus of the reef: a mantle to 22 cm (9 in) and arms to 80 cm (31 in), usually found not as an animal but as a pile of empty shells outside a hole in the coral. That midden is the reliable way to locate one, because the octopus itself will be whatever texture and color the rock behind it is.

The camouflage runs on hardware no other animal has. Millions of pigment sacs in the skin are wired directly to the brain and open or close in milliseconds, while separate muscles raise the skin into spikes and ridges to change its texture. One study counted an animal changing appearance around a thousand times in seven hours. It does all this while being, as far as anyone can tell, colorblind.

One display is hunting rather than hiding. When a crab freezes rather than fleeing, the octopus runs a dark band across its own body toward the prey, over and over, like a shadow passing. The crab breaks and runs, and running is fatal. This trick, called the passing cloud, is one of the few known cases of an animal using a moving image on its own skin as a tool.

Unlike most of its relatives it hunts by day, especially at dawn and dusk, walking over the reef with its arms spread in a web and dropping the whole membrane over a coral head to trap whatever is inside. It lives about a year, breeds once, and dies.

## Also known as

- **English:** big blue octopus, Cyane's octopus, day octopus
- **German:** Großer Blauer Krake
- **Japanese:** ワモンダコ
- **Chinese:** Lán-Xiāo, 土婆, 藍章

## Scientific synonyms

- *Callistoctopus magnocellatus* Taki, 1964
- *Octopus cyanea var. gracilis* G. C. Robson, 1929
- *Octopus glaber* Wülker, 1920
- *Octopus herdmani* Hoyle, 1904
- *Octopus horsti* Joubin, 1898
- *Octopus marmoratus* Hoyle, 1885
- *Sepia barffi* Curtiss, 1938

## Range

Comoros, Eritrea, Federal Republic of Somalia, Indian Ocean, Kenya, Madagascar, Mozambique, New Zealand, Red Sea, Republic of Mauritius, Seychelles, South Pacific Ocean, Tanzania

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/molluscs/cephalopods/big-blue-octopus)*
*Updated: August 23, 2026*