This octopus from the Maldives lead me to a few facts and numbers I wasn’t expecting at all. Fascinating creatures in a complex world is the motto.
The identification is very vague. There’re three species of diurnal octopus listed on sealifebase.se for the Maldives. O. cyanea is often dark red, sometimes dark brown with a broad, vertical white line on the mantle. I couldn’t find much about O. gardineri, maybe because it is benthic. O. vulgaris is often light brown, without much of a pattern.
Besides the Day octopuses, there are several species of Night octopus (genus Callistoctopus). The photos reveal it, I must have seen one of the the Day octopuses, because it was day. I have no idea if that’s correct though. How can you identify an animal that changes its appearance within seconds?! When you look at my photos, you might look at different species, photos are not enough to identify species.
Octopus cyanea was described in 1849 by John Edward Gray. Norman (1991) explains that it was named after Cyane, a Greek nymph, and doesn’t directly refer to blue (cyan), so it is not O. cyaneus. There has been confusion though, and the wrong name O. cyaneus is sometimes found in literature. Cyane dissolved in tears as she couldn’t stop Hades from abducting Persephone. Her name does mean blue of course, probably because she turned into a pool of deep blue water. I can’t say that I have ever seen any hint of blue on an octopus under water. But the biologists of course examine animals on land, and they will see them literally in a different light.
What we all know about octopuses is how smart they are, some compare their cognitive abilities to those of a rat. They have 8 arms, and there is a funny anecdote here. Over the past centuries different names were used for the octopus. Polypus was in the race in ancient Greece, and it took an official decision of the International Commission on Zoological Nomenclature to eleminate this less precise name. ICZN opinion 233: specific name of type species of Octopus Cuvier, 1797, (1954:278)]. Johann Gottlob Theaenus Schneider published the name Polypus (as species of the genus Octopodia) in 1784, but made some mistakes. There’s 17 pages of explanation why his names are not accepted. William Elford Leach established the genus Polypus in 1817, and it was also mentioned in Opinion 233. It is considered a synonym of Octopus. All this happened in Paris, 26. July 1948, a Monday, at 8:30pm. Read the story about the name on grammarphobia, where it is also explained why the plural is not octopi!
Don’t think a smart animal has an easy life. I usually see octopuses hiding during the day. As soon as they swim, they have to tuck in the arms, because fish, often triggerfish, bite the tips. When you happen to see an octopus hunting, you’ll often see fishes near them. I’m not sure how much they support each other. To me it looks more like competition. I saw octopuses knocking fishes away while hunting, because the fish got too close.
There’s 8 arms, each with kind of a brain, plus a main brain, makes 9. 3 hearts keep the mollusc alive. That’s already slightly advanced knowledge here.
What I did not have ready is the enormous number of eggs they lay. Hundreds of thousands! Like many or most marine creatures, octopuses also start their short lives as tiny plankton. Females live for just a year or two, and their death has it in it. You might have heard that the female will protect the eggs, and even stop eating during that time.
You would think they starve to death, but for some reason which I totally don’t see, nature built another mechanism to ensure the female will die. And there’s something new, published in 2022. US scientists from the University of Washington and Chicago (Wang et al.) discovered the molecular structure of the substance that causes the death of adult octopues.
There is a gland between the octopus eyes, that produces hormones which are important for different steps of the reproduction. The final step is a hormone called 7-dehydrocholesterol, short 7-DHC, that does not simply cause death. I did not know that they harm themselves, and kind of self destroy themselves. The purpose of this destruction is thought to be protection of the offspring from the cannibalistic mother. That has a huge limb to me. The difference in size. An octopus egg is only 1 to 3mm long. I do not believe a large female octopus feeds on tiny plankton. The smart octopus shouldn’t be tempted to eat his own eggs while protecting them, like literally all mothers protect their offspring for a certain time.
Also, the tiny octos are plankton, while the females live on the ground, so they wouldn’t even meet, until the little ones reached a certain size. Could it be the other way? Is the mother the first meal for the offspring, before they start planktoning around?
Anyways, here’s the story. The exact hormone that causes the octopus to self harm, and eventually to die, can also be found in the human body. A genetic mutation called Smith-Lemli-Opitz syndrome (SLOS) is closely related to it. And it has one common symptom, which is self harm. How fascinating that so different organisms show so similar reactions to one hormone. David Weyhe Smith also worked in Washington’s University, Luc Lemli and John Marius Opitz at the University of Wisconsin–Madison. Meta AI gave me an estimation of 20.000 people living with SLOS.
This ‘senescence’ called process is not exclusive to females. Males suffer the same death. I wonder if this short live is a highway for evolutionary changes in a species. High predatory pressure is thought to be one driver for short lifespans, and the high number of eggs supports this theory. But it doesn’t help me to understand why their bodies would self destroy. Perhaps its just a coincidence that their bodies produce this 7-DHC, and it has no deeper meaning. Scenescence could be just a side effect?!
One more fact cannot be ignored, since it shocked me big times. Studies about catch quotes for octopus are devastating. In 2020 380.000 tonnes of octopus were caught for consumption. When we assume an average weight of 2kg per octopus, that would be 190 million animals, per year! I can’t believe or imagine that. The Spanish company Nueva Pescanova became famous for its plan to farm Octopus vulgaris in Las Palmas de Gran Canaria. Read more here!
A species of Octopus in the Maldives, possibly O. cyanea
Another Maldivian reef Octopus, maybe O. vulgaris
Two octopuses interacting, note the white line on the white specimen’s mantle. Possibly O. cyanea
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