12 Things You Need To Know About Octopus, Squid & Cuttlefish

doug seifert blue ring octopus

The venomous blue-ringed octopus (Hapalochlaena sp

You find them in every ocean, in every marine environment. They come in all shapes and sizes. They have been around for more than 490 million years.  They are the cephalopods - octopus, squid, cuttlefish, sepiolids and nautilus. Douglas David Seifert celebrates one of the ocean's most successful life forms. Here are 12 fascinating facts…

1) Cephalopods survived the Permian-Triassic extinction event which killed off 95% of marine life and the Cretaceous extinction which eradicated 90% of all existing animals.

2) Coleoid cephalopods (octopus, squid, cuttlefish & sepiolids) have three hearts and transport oxygen in their bloodstream via copper-based hemocyanin - making them true blue bloods.

SEIFERT.BobtailSquid MG 50861

The diminutive bobtail squid (Euprymna berryi)

SEIFERT.ChamberedNautilus MG 5895 1

The emperor nautilus (Nautilus pompilus) is the largest of the six nautilus species

3) In the cold and perpetual blackness of the deep sea, the eggs of the Graneledone boreopacifica octopus take four-and-a-half years to develop, making it the longest known incubation in the animal kingdom.

4) Octopus are the only cephalopods to tend their eggs until they hatch: squid, cuttlefish, bobtail squid and nautilus deposit their eggs and never look back.

SEIFERT.GiantCuttlefish C7T3072 1

Broadclub cuttlefish (Sepia latimanus)

SEIFERT.Octopus C7T9852 1

The suckers of a day octopus (Octopus cyanea)

5) More than 11,000 different species of cephalopods have been identified in the fossil records dating back nearly 500 million years.

6) Octopus, squid, cuttlefish and sepiolids can change their skin colouration in 200 milliseconds - a fraction of a blink of an eye.

SEIFERT.PygmyCuttlefish MG 1308 1 copy

A dwarf cuttlefish (Sepia bandensis)

SEIFERT.SquidVB1Y7426 1

A bigfin reef squid (Sepioteuthis lessoniana)

7) Bigfin reef squid have the fastest growth rate of all cephalopods, growing as much as 600 grammes in a four-month growth spurt.

8) The nautilus is the only cephalopod that retains an external shell. They remain relatively unchanged from their first appearance 360 million years ago; a so-called ‘living fossil’ – with the six remaining species found in the Indo-Pacific.

9) Octopus have the largest brain-to-body mass ratio in the invertebrate world, larger than many vertebrate species.

10) The heaviest of all invertebrates is the colossal squid (Mesonychoteuthis hamiltoni) which can tip the scales at 495kg. And a cephalopod is also the longest invertebrate as the giant squid (Architeuthis dux) can reach a length of 12m. 

SEIFERT.Wonderpus N816705 1

The wonderpuss octopus (Wunderpus photogenicus). Wunder is German  meaning 'marvel or wonder'

11) Cephalopods are increasingly being targeted for food. The global catch of cephalopods is 4.8 million tonnes (3.5 million tonnes of squid and 350,000 tonnes of octopus) with a commercial value of USD$10 billion.

12) Size dimorphism between the larger female and smaller males is common among cephalopods.





Love diving? You'll love these. Sign up today to immediately download our unique FREE gifts -

AROUND THE WORLD IN 80 WRECKS - DIVE's 70-page, beautifully illustrated, colour guide to the world’s best wrecks

SCUBA STORIES - DIVE's collection f real life stories where divers, who have got themselves into perilous situations, describe how they reacted and what actions they took to ensure they lived to tell the tale

PACIFICHighlights of the Pacific - Dancing mantas in Hawaii • The Best Diving in the World, Galápagos, Cocos, Malpelo & Socorro • Mass Spawning Events in Palau

New Upright Gift Banners 300 x 600 px

Sidebar SUBSCRIBE spring 21 large2

Destinations Spotlight

Need inspiration for your next dive trip? Try one of our featured destinations from DIVE's travel partners.

sidebar philippines sidebar bahamas sidebar mexico sidebar fiji sidebar st helena 2020 Sidebar Egypt sidebar banner sabah sidebar banner belize sidebar banner south africa

DIVE Partners

sidebar banner egypt new ceningan divers ad 300x100 LH 300 min giphy subex Wakatobi Siladen Aggressor Fisheye Dive Worldwide gozo banner Arenui

Read DIVE magazine

DIVE magazine is available to read on many devices. Simply click one one of the options below

PCMac final
Apple finalAndroid final

Like what you see?

Join us on social and keep updated daily...