Octopuses

The octopus is a soft-bodied mollusc with 8 limbs (also known as tentacles). About 300 species are recognized, and the order of Octopoda is grouped within the class Cephalopoda, along with squids, cuttlefish, and nautiloids. The octopus is bilaterally symmetric, with one side the mirror image of the other.

The 8 appendages of an octopus trail behind them as they swim, which they do by expelling a jet of water. With 8 arms to control, they have a complex nervous system. They also have excellent sight and are among the most intelligent and behaviorally diverse of all invertebrates.

With so many types of octopuses, they are found throughout the sea, from seashores to the abyssal depths. Most species grow quickly and don’t live very long. In most species, the male dies after mating, while the female watches over the fertilized eggs until they hatch, then she dies.

The octopus has many strategies to defend themselves, including the expulsion of ink, the use of camouflage and threat displays, the ability to jet quickly through the water and hide, and even deceit. Only one specie is known to be deadly to humans, although all octopuses are venomous.

The largest known octopus specie is the giant Pacific octopus. Adults usually have an arm span up to 14 ft (4.3 m) and weigh around 33 lb (15 kg). The largest specimen scientifically documented weighed 156.5 lb (71 kg), but much larger sizes have been claimed for the giant Pacific octopus, including one that weighed 600 lb (272 kg) with an arm span of 30 ft (9 m). A carcass of the seven-arm octopus was estimated to have a live mass of 165 lb (75 kg).

The smallest specie is octopus wolfi, which is about 1 in (2.5 cm) and weighs less than 0.035 oz (1 g).

The bulbous head of the octopus contains most of the vital organs. Lacking any bones at all, even large specimens of octopus can squeeze through a 1 inch gap, which can make them quite the escape artist!

I think we all know that the tentacles can bend in any direction at any location, and that the interior surface of the tentacles are covered in circular suckers. But I didn’t know that the octopus typically uses 2 tentacles to ‘walk’ along the sea floor, while the other 6 are used for foraging.

Octopuses have 3 hearts; a systemic heart that circulates blood around the body, and two branchial hearts that pump blood through each of the two gills. The systemic heart is inactive during swimming, so the animal tires easily and prefers to crawl. Their blood contains a copper-rich protein to transport oxygen. This makes the blood very viscous and bluish in color, but it transports oxygen more efficiently in cold water with limited oxygen availability than hemoglobin.

In several sets of mythology, octopuses appear as sea monsters, from the Kraken of Norway to the Gorgon of ancient Greece, and probably many more.

I saw a tv episode once on what evolution would do with today’s species in another million years, and one of the things suggested was that at least one specie of octopus would leave the sea to seek food in the forests on land. While this is an intriguing thought, I wonder if the octopus would have to develop some kind of support for its internal organs, to keep them from dragging along the ground, or a thick skin that could resist tearing and leaving those organs scattered behind it. Because it isn’t exactly dealing with the full force of gravity while it’s in the water, but it would have to once it came ashore.

 

https://en.wikipedia.org/wiki/Octopus