Header image credit: Bill Abbott / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.0)
Are you interested in malacology, specialising in teuthology? Then you have come to the right place, since today’s Kreature Feature will be about the giant Pacific octopus. Malacology is the study of marine molluscs. Teuthology is a sub-set of malacology, as it is the study of cephalopods specifically.
Octopuses (yes, that is the plural of octopus) belong to the class cephalopoda. This class also includes the squid, cuttlefish and nautilus. What defines cephalopods is their bilateral symmetry, a very pronounced head, and several arms. All cephalopods are molluscs, which makes them cousins of snails and mussels. This is usually not the first family connection one makes, since octopuses are a lot more complex than the average mussel. Octopuses are considered to be the most intelligent invertebrate, because they have been observed problem solving and using tools.
The word octopus is derived from ancient Greek and means eight legs. The octopus of this Kreature Feature is the Giant Pacific octopus (Enteroctopus dofleini). The genus enteroctopus was first described in 1889 by Alphonse Trémeau de Rocherburne and Jules François Mabille. They were both French malacologists, and thousands of species of molluscs were described by these two zoologists. The word enteron, in enteroctopus, comes from the ancient Greek word for gut. I am not sure why this octopus genus has a name relating to intestines, but one amazing thing about them is that they are the largest known octopus species in the world. There are four species in this genus and the Giant Pacific octopus (let’s call it GPO for short) is the largest octopus ever recorded. But more of that in a moment. The species name of the GPO is dofleini. It was described in 1910 by someone called Wülker, but unfortunately not much more information is available. The GPO was formerly known as Octopus apollyon. The word apollyon means destroyer and is also sometimes used as a reference for the devil. This description probably stems from the mythological stories of giant sea monsters, like the Kraken, which are actually based on the giant squid.
The range of the giant Pacific octopus, found along the shores of the major continents bordering the Pacific ocean (Image: Connormah / Public domain)
The largest GPO ever recorded was 9 m long and weighed a hefty 272 kg. This is an exception, however, as most reach about 5 m in length and up to 50 kg. Still, they are big and would give any diver a fright if encountered underwater. Octopuses, in general, do not live very long. The GPO, however, has the longest lifespan of any octopus, at up to five years. The end of life of an octopus is a direct result of mating. When octopuses mate, it always leads to the death of both partners. The female octopus only mates once in her life. Once she has laid her 20 000 to 100 000 eggs, she looks after the eggs until they hatch. She guards them from predators, cleans and fans them with oxygenated water. Incubation can take up to a year and the female octopus does not leave the eggs under any circumstance, even to feed. Essentially, she is starving herself to death. At the same time, she enters a period of senescence (the process of aging) and shortly after the baby octopuses have hatched, she dies. Males can breed with several females, but also enter a period of senescence and tend to die within three months of the mating process.
Before the ultimate sacrifice of mating and dying, GPOs live their first three to four years undergoing rapid growth. After hatching from an egg, they live a planktonic life for the first three months of their life. After that, and once large enough, they live on the sea floor and hunt for food. GPOs tend to live anywhere from rock pools to 110 m deep. Some have been observed at depths of up to 1 500 m, so they can clearly inhabit the deep ocean easily. Once they have established a home range, which is around five square km, GPOs are solitary and reclusive. They leave their dens to feed, or to mate. Only leaving your home to find food is a very relatable lifestyle in our current lockdown life.
GPOs are carnivores and prefer eating clams, fish, crabs, and their cousin, the squid. They ‘prepare’ their meals in different ways, by pulling clam shells apart, or by cracking a crab carapace open with their powerful beak. Most commonly, however, the GPO drills holes into its prey, if it has a hard shell, and injects toxic saliva into it. This will paralyse the prey and will make it easier to eat. GPOs like to eat at home, so once they have caught their prey, they take it back to the den. They are also very neat and deposit any shells and bones outside of their den entrance once done. These deposits are called middens and are a great way to find out what an octopus eats. What eats a GPO? Not many animals, primarily some of the larger marine fish and mammals, if they can catch them. Sometimes they also end up on our dinner plates, however there is no designated fishery for them.
Giant Pacific octopuses feed on a range of animals (Image credit: Christianreno / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0))
Octopuses are renowned for their amazing camouflage skills and can hide in plain sight. They do this with specialised cells called chromatophores and iridophores. Chromatophores enable octopuses to blend in with surroundings that are yellow, red or brown, but of course there are more colours than that in the ocean. This is where the iridophores come into play. Iridophores are another layer of thin skin that are reflective, which means that they can reflect colours found around the octopus. The angle of the reflection will define what colour will be expressed and, together with the chromatophores, enable octopuses to completely disappear if they need to. Just to make them even more amazing, they have a third type of cell called a leucophore, which enables them to turn white. The leucophores intensify the colours produced by the chromatophores, by giving them a white background. They also reflect colours, but differently than the iridophores. Lastly, just changing colour is not enough sometimes. Looking and feeling like the object you are trying to mimic is important too. This is where another group of cells, papillae, come into play. Octopuses use visual cues, not tactile ones, to figure out the texture of the object they are trying to blend into. Their papillae can then change the shape and texture of their skin to mimic whatever background they are hiding on.
If all the colour changing and skin morphing does not work, or there is no time for it, an octopus can also eject a jet of ink as they make a quick getaway, leaving behind a confused predator. Octopuses truly are the magicians of the ocean and one of the coolest animals, ever, (in my humble opinion). The giant Pacific octopus has to be regarded as the king or queen of all octopuses and truly an amazing animal.
Sea you next time for K’s Kreature Feature!
Want to learn more about octopuses? Check out My Octopus Teacher on Netflix South Africa.
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Claudine van Zyl completed her Work Imtegrated Learning (WIL) internship with us last year. Her research project was: ‘The characterisation of plastics in stranded post-hatchling loggerhead turtles along the South African coastline from 2015 to 2020’.