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Comparing physiologies: Giant Pacific octopuses

giant Pacific octopus swimming in the ocean

Fun Fact

The giant Pacific octopus has three hearts, nine brains and blue blood.


When I was young, my father told me that my tummy rumbled because I needed to power my engine by eating. I confess I thought that a small steam train was doing loops inside me. It either says a lot about my imagination or a lot about my Dad’s level of persuasion!

Children can have some interesting perspectives on what is inside them. Cultural perceptions can also make a huge difference. Why not investigate their prior knowledge by starting a conversation about the biology of the Pacific octopus or another sea creature they have studied?

Where to start

The Pacific octopus is a fascinating creature. Learn about its anatomy and life with the children. You can use this approach in numbers:

1 Pacific octopus 

2 eyes

3 hearts

4 years – their average lifespan

5 metres – the biggest is nearly 5m long

6 months – a Pacific octopus mum watches her eggs for half a year

7 clams for afternoon tea

8 arms

9 brains

How is the Pacific octopus different from us? The children can start to compare their own anatomy to that of the octopus by investigating their own bodies: Where do they think their heart is? Can they feel it beating? What does it do? What colour is their blood? Where is their brain? How tall are they? Why do they think they have two eyes? Can they think of an animal that has more than two eyes? Imagine if they had a brain in each of their legs! What would that be like? This is also a great way to assess their prior knowledge.

What’s the STEM?

The children are comparing their physiology to that of a sea creature and become more aware of how their own body functions.

Interesting facts for adults

The giant Pacific octopus is a cephalopod, which is Greek, meaning head foot. Octo means eight, relating to its eight arms. Based on observations, octopuses use two of their limbs like legs and only six like arms. Despite the joke, “How do you make an Octopus laugh?” – Give is tentickles,” it is incorrect to call its arms tentacles!

Each of its arms has its own brain that controls movement. It allows them to work individually but still function as a whole. It also has a central brain that controls the nervous system. That’s nine brains total! They are very clever and can open jars, mimic other octopus species and tackle mazes.

They live for up to four years. A pacific octopus mum watches her eggs (up to 74,000) for seven months without eating or leaving the crevice in which she laid them.

Observations, conclusions and extensions

Maybe the children would like to draw their own sea creature that could be a mixture of all the sea creatures they know. They could also make up scenarios exploring what life would be like if their physiology was different: What would life be like if they had eight arms? What if everyone had eight arms? Can they design a car or a bicycle for someone with eight arms?

What other animals have you investigated with the children in your care?
Share your experiences using the comments section below. 

Hayley Bates
Article author: Hayley Bates
National Certifications Coordinator

Hayley has an insatiable thirst for learning – about everything! Her sheer joy of discovery and passion for professional development makes her the perfect person to run the Little Scientist’s House Certification program.

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