The octopus (Greek Októpus meaning eight foot) is a cephalopod mollusk that belongs to the order Octopoda. This animal has 4 pairs of arms, 2 eyes, a beak within a mouth at the center of the arms, and has no internal or external skeleton (though some retain a remnant of a shell within the mantle).
Octopuses (yes, this is the grammatically correct plural) are fascinating creatures! Firstly, they are in fact very old – there is an octopus fossil from 296 million years ago! How can a boneless creature have formed into a fossil you may ask? Apparently, it appears to be more of a blob, but with close examination 8 legs and 2 eyes can be seen. Originally, octopuses were thought to be unintelligent, but more recently they have been seen to be very clever creatures able to navigate mazes, solve problems and remember the solutions, and escape from seemingly secure tanks. Indeed, their heads are not the only intelligent parts of their bodies – two-thirds of an octopus’s neurons are within its arms, not its head. This means that the arms are able to solve the problem of opening a shellfish while the octopus investigates a new nook or cranny. This also means that the arms react to pain stimulus even after being severed from the body!
Their unique physiology doesn’t stop there! Octopuses have 3 hearts, and they do not all function the same. Two of the three hearts pump blood to the gills, while the third circulates blood to the organs. When the octopus swims the heart pumping blood to the organs stops working, which is why one will more regularly see an octopus stealthily crawling along rather than swimming. Octopuses do not have blood like ours, theirs is copper-based blood known as hemocyanin instead of iron-based blood. Hemocyanin is more efficient at oxygen transport in cold waters and low oxygen availability. However, this leaves octopuses very sensitive to changes in the acidity of the water which is a concern due to climate change induced ocean acidification.
Perhaps the most you knew about octopuses was regarding which parts to eat and the many ways of preparing them – almost 270 000 tons of octopus is imported by various countries yearly! Calamari is a tasty and popular meal!
Written by: Minke Witteveen
For further reading:
- Nuwer, R. 2013. Ten Curious Facts About Octopuses. Accessed: 27-03-2016. URL: http://www.smithsonianmag.com/science-nature/ten-curious-facts-about-octopuses-7625828/?no-ist
- Courage, K.H. 2013. Octopus! The Most Mysterious Creature in the Sea. Penguin Group: New York.