Octopus - travel methods and great deal of other information.

Octopus – The Great Mollusk

OVERVIEW

Also known as the ‘Devil-Fish’ due to the terror their strange appearance caused early sea-farers the Octopus or “Eight Footed” cephalopod refers to the Genus Octopi, which are members of the Phylum Mollusca of the class Cephalopoda, order and family Octopoda. Characterized by their having eight “legs” which are more accurately referred to as arms, a lack of skeletal structure and unique locomotion capabilities the Octopus is an often misunderstood and much maligned creature.

Each of the octopus’s arms have two rows of suction cups each of which has ‘taste sensors’ to allow it to identify food. With the ability to regenerate lost arms and an eye on each side of its head Octopi are hardy predators with unique self defence mechanisms and very good eyesight. They are however deaf.

Most Octopi have a globe-shaped ‘head’ or mantle that contains all the vital organs and mouth which hold a sharp beak which is used to kill and decimate prey. Their skin is smooth and ranges in color most normally from a tan to light brown with some coloration, but many are able to change colors by contracting skin cells filled with pigments to allow it to hide when hunting for prey. Some Octopi can even mimic other fish and objects, and their defensive arsenal includes the ability to squirt an ink like substance at an attacker to mask their getaway.

With life spans of approximately two years Octopus are often confused with squid, another Cephalopoda which has two longer arms called ‘tentacles’ – in an octopus all eight appendages are of a similar length and are called ‘arms’ not legs.

Living primarily in dens which provide refuge from predators including other octopi and various fish their staple consists primarily of crustaceans and molluscs such as crabs and scallops. This diet is supplemented by other bivalves, snails, fish and even other octopi. They gain access to shelled prey either by pulling it apart, biting it with their beak to break it apart or by drilling through the shell and secreting a toxin to dissolve the connective tissues.

Although difficult to maintain in captivity it is not unheard of for some people to keep them as pets, although they are very sensitive and their short life span discourages many would-be owners, as does the ability to escape from even well secured tanks due to their well known problem-solving abilities and high intelligence, which has been compared to that of an average house cat. They also are a food source in many parts of the world and some species are even bred and raised exclusively for that purpose.

A misconception is that octopi eat their own arms when stressed – but studies have show that this behaviour is caused by a virus that attacks the nervous system although stress may allow the virus to attack more readily.

There are over 160 different species of Octopus, broken into two large groups:
• Cirrata: Finned octopi that live at depths between 1,000 and 24,000 feet
• Incirrata: non-finned shallow water dwellers
Octopus have a sharp beak that it uses to crack shells and inject poisons and digestive fluids into shellfish and other prey.

OCTOPUS TRAVEL METHODS (LOCOMOTION)

The primary locomotion is to crawl or swim which is achieved via their arms. This allows the octopus to use their suckers to sense any molluscs or food they come into contact with. For fast locomotion however, all octopi have a somewhat unique ability to circulate water through their mantle cavities. While this is primarily used for respiration and waste removal it also is used for rapid locomotion. In addition to providing rapid locomotion octopi have been seen to use this ability for cleaning of dens and to repel pests.

It is not unheard of for Octopi to leave the water for brief periods, and in fact octopuses kept as pets have been known to escape their containers and invade nearby aquariums to utilize the fish as a food source. This unique ability led to a recent Octopus hoax about an ‘endangered species’ of octopi called the ““Pacific Northwest Tree Octopus aka Octopus paxarbolis” which is NONEXISTENT! This interesting faux variant is now often touted as real since being quoted in a research paper but does NOT exist. Supposedly an Octopus found only in the Pacific Northwest it was said to be amphibious, spending only their early life and mating season in the water. I mention it here to help end the misinformation.

CRAWLING

Most commonly the Octopi crawl, using their legs in a scuttling motion to push and pull themselves along a surface or the ocean floor. Crawling is interesting since they do not have full control over their arms, they simply send a high level command for movement and it sorts itself out!

WALKING

There are several species that actually ‘walk’ in the classic sense, using two alternating arms in a rolling gait and utilizing the remaining arms for camouflage: they are the

• Octopus marginatus – which resembles a coconut
• Octopus aculeatus – which appears to be a clump of floating algae

JET PROPULSION

The fastest method of locomotion is the direction of water through their mantles as mentioned previously. During this process water flows into the mantle across the gills from an opening in the head. The octopi builds pressure by sealing off all orifices except for a path called the “funnel” or “siphon” and uses the thick muscles of the mantle wall to squeeze the water out the narrow funnel. Able to reach speeds of 25 miles per hour with this method of travel they utilize it normally only in dire circumstances since their ability to maintain it is limited.
To steer they simply adjust the direction of the funnel and can use it to trap prey in rapid movements as well as shoo away pests and to agitate predators.

Greater Blue-Ringed Octopus (Hapalochlaena lunulata)

FLYING

Even more astonishing is the fact that some octopi have been known to ‘fly’ by blasting themselves out of the water completely to escape predators. Several varieties of squad have also been known to accomplish this feat.

SWIMMING

The finned variety of Octopus, known Cirrata can use their fins as balance and propulsion similar to a fish. They may also use their fins in combination with their funnel, for direction control.