Cephalopods (squid, octopuses, cuttlefish and nautilus) continue to captivate people’s imagination with their remarkable diversity in size and behaviour. Adaptations for predation, locomotion, disguise, and communication demonstrate the exciting, yet largely unknown science of cephalopods.

Born killers

All cephalopods are active predators (with the possible exceptions of the bigfin squid and vampire squid). Crabs are the most common choice of prey, however, giant squids are thought to eat sperm whales on occasion! Many cephalopods are smart, fast predators that inhabit all oceans on earth and occupy a majority of the depth of the ocean too, from the abyssal plain to the sea surface. The variety of hunting techniques cephalopods exhibit is due to their ability to adapt and learn, using encounters with prey to refine their strategies.

The Humboldt squid (Dosidicus gigas) swims at speeds of up to 24 km/h (15 mph) through jet-propulsion and their tentacles bear 100–200 suckers, each lined with razor-sharp teeth, with which they grasp prey and drag it towards a large, sharp beak. Humbolt squids hunt alone but also in large coordinated groups of up to 40 individuals.





Changing colour

Cephalopods have the wonderful ability to change colour by using numerous pigment-filled bags, called chromatophores. Chromatophores are found in the skin and expand and contract to reveal or conceal small dots of colour. These colour changes are used by cephalopods to aid in camouflage, communication and courtship rituals.

The mimic octopus (Thaumoctopus mimicus) can alter its colour, shape and behaviour to imitate a variety of species to avoid predation. Species they mimic include, sea snakes, flounders and lionfish!

Mimic Octopus Changing Color, Shape and Behavior

by Talal Masood





Blue blood

Yep, you read that right. Blue. Blood. Cephalopods have a closed circulatory system which co-transports both blood and water. Hemocyanin, a copper-containing protein, rather than haemoglobin, transports oxygen in the blood. Consequently, when deoxygenated, their blood is colourless but turns blue when exposed to air.





Three hearts

It all just got weirder, yes, cephalopods have three hearts! Two of these three hearts are branchial hearts (also known as gill hearts) on the left and right side of the body. Each branchial heart moves blood through the capillaries of the gills. This allows efficient gas-exchange (of O2 and CO2) to take place across the gill. The third heart is a single systemic heart that pumps the oxygenated blood through the rest of the body.





Intelligence

Arguably the most fascinating characteristic of cephalopods is their intelligence. Cephalopods have a highly developed nervous system and the largest brain to body mass ratio of the invertebrates. This has contributed to their status in the academic world as ‘honorary vertebrates’ protected by experimental legislation in the European Union. Often described as ‘sentient’, these curious creatures are known for their strong ability to learn through experience, have shown complex social behaviours (with the same species and other species) and shocked scientists with their ability to problem solve and use tools!

















A coconut octopus (Amphioctopus marginatus) using a nutshell and a clamshell for shelter.

by Nick Hobgood













It’s crazy to think that animals as beautiful as cuttlefish and as intelligent as the octopus do not live beyond the age of two!





So there you have it, 5 reasons why cephalopods are fascinating. What are your favourite things about cephalopods? I would love to hear your thoughts.





If you enjoyed this article please like and/or share!





#science #biology #cephalopods #octopus #squid #cuttlefish #intelligence #nature #oceans #environment

Resources

1. Benoit-Bird, Kelly J., and William F. Gilly. "Coordinated nocturnal behavior of foraging jumbo squid Dosidicus gigas." Marine Ecology Progress Series 455 (2012): 211-228.

2. Ghiretti-Magaldi, A. (October 1992). "The Pre-history of Hemocyanin. The Discovery of Copper in the Blood of Molluscs". Cellular and Molecular Life Sciences. 48 (10): 971–972.

3. Godfrey-Smith, Peter. Other minds: The octopus and the evolution of intelligent life. London: William Collins, 2016.

4. Nixon, Marion, R. E. Allen, and John Zachary Young. The brains and lives of cephalopods. Oxford University Press, 2003.

5. Williams, Wendy. Kraken: The Curious, Exciting, and Slightly Disturbing Science of Squid. Abrams, 2011.

6. Wells, M.J. (1 April 1980). "Nervous control of the heartbeat in octopus". Journal of Experimental Biology. 85 (1): 111–28.