The octopus is considered the most intelligent of all invertebrates. Increasingly scientific studies confirm that they are sentient creatures, able to learn easily besides observing other octopuses. With their eight arms and giant egg-shaped head, octopuses are one of the most alien-looking creatures on the planet; this has made them the object of maritime horror-stories for centuries.
The octopus has blue blood, three hearts and gills like fish, which means they depend on water to breathe. But despite this fact, many species of octopus leave the water for short periods of time to hunt for stranded crabs on land. Nearly all octopuses are predatory; bottom-dwelling octopuses eat mainly crustaceans, polychaete worms, and other molluscs such as whelks and clams; open-ocean octopuses eat mainly prawns, fish and other cephalopods.
Dolphins, sharks, moray and conger eels will all feed on octopuses. Luckily, the octopus can regrow lost limbs just like starfish and can even close off the severed artery to reduce blood loss. When they bleed, their blood is not red but blue because it is high in copper instead of iron. Sometimes they will even deliberately sever an arm to distract predators long enough to swim away at top speeds of 40 km/h (25mph). For protection they use weapons found on the ocean floor in form of rocks or shells, carry forts for hiding and make barricades to keep off predators. The most impressive survival tactic is their skin; with changing texture and color they blend in with their surroundings to avoid detection by predators. Not only do they have three hearts and blue blood, but they can create clouds of dark liquid in order to conceal themselves from enemies. An octopus’s brain is located in its egg-shaped head, called the mantle. But the brain is not the only control mechanism, each arm contains enough neurons to operate semi-independently. (https://en.wikipedia.org/wiki/Octopus)
You can find out much more about this amazing creature in the video clip at the end of the blog. Please take the time to watch - it will be worth it!
Causing a great surprise is another astonishing fact: Octopus can detect early warning signs of volcanic eruptions.
In a place like no other, where fire and water meet, the battle for survival rages on. Stromboli is an island in the Mediterranean (of Sicily) with one of the most active volcanoes on the planet. Lava and debris constantly pour into the sea. Beneath the surface, a healthy population of common octopus survive.
It turns out that the octopus has special skills knowing when to flee in time before an eruption is about to occur. Eruptions from the summit craters typically result in a few short, mild, but energetic bursts, ranging up to a few hundred meters in height, containing ash, incandescent lava fragments and stone blocks. Through high-tech sound recording, scientists now know that the octopus can hear very low sound frequencies of 1 to 4 hertz. (http://scribol.com/environment/animals-environment/how-the-octopus-survives-strombolis-constant-volcanic-eruptions/)
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Enjoy the following video:
How many hearts does an octopus have? How do species like the mimic octopus camouflage themselves? Find out about these and other octopus facts.
Nat Geo Wild (4:09)
Epilogue: “Octopus as Food - but is it sustainable?”
Octopus is mainly caught using trawl fishing gear. Studies have identified that trawling for octopus and squid has damaged large areas of coral reef habitat in parts of Southeast Asia.
Regional assessments of fisheries indicates that in general, high fishing pressure on a range of species, including octopus species, in coastal waters has led to declining catches across the region, with many species of octopus now overfished.
China also has a large distant water fishing fleet, which means that the vessels fish around the world, not just in waters bordering their country.
All octopus destined for the US sushi market for example is processed in Japan and labeled “Product of Japan”, so identifying the origin of octopus sushi is nearly impossible.
http://seafood.edf.org/octopus
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REFERENCE
Australia’s Sustainable Food Guide (viewed 13.12.2018)
https://www.sustainableseafood.org.au/fish.php/1/65/octopus
One Kind Planet (viewed 13.12.2018)
The Irish Journal, 2016 (viewed 13.12.2018)
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