The Amazing Octopus
The octopus is a mollusk and has that phylum's characteristic traits, among them, Its "muscular foot" which has evolved into parts of its head and eight tentacles. Unlike its mollusk counterparts it has done away without any shell, internal or external, much as slugs have shed their snail shell. The resulting body is one of great agility and dexterity at the cost outer production.
Octopi have eight arms or tentacles which have a great deal flexibility. They are also laden with suction cups on the bottom, not just for movement but also for touch and taste, the suction cups contain chemo sensors that allow the octopus to taste the world around it. The octopus also has a developed sense of touch as well. Given the range of dexterity and sensation, it should come as little surprise that octopi are highly curious animals, feeling and tasting their way around the environment.
The octopus has three methods of getting around. Either it can crawl over an area of its tentacles, swim, or propel itself through water jets (which send the octopus flying head first with its tentacles trailing beyond it. In either case the octopus has both complex eyes and statocysts that detect changes in orientation. This allows the octopus (like human beings) to focus their eyes on one object even when they are moving.
Predators and Predation
All octopus species are carnivores, but their lack of a shell puts them in danger as well. One adaptation that addresses both issues is the development of chromatophores, pigment cells that can rapidly change the color of the creature. This is better developed in some species more than others, but the octopus is a master of disguise. This lets it trap its prey without alerting large animals. The octopus can also (notoriously) squirt out jets of ink. Most of this substance is melanin (the pigment responsible for skin color) and it can serve a number of purposes from temporarily blinding predators by sight but also by smell. One of the intended effects is for the predator to attack the ink blot while the octopus finds some place to hide. Even without these adaptations the octopus is no light weight, as the next video shows.
Among these array of exotic features, it is octopus intelligence that is truly remarkable. Given the need of the octopus to go find prey combined with its complex body leads the octopus to a complex brain, probably the most complex in the invertebrates. Experiments confirm that an octopus both remembers and learns in a variety of ways, including classical conditioning. Moreover the octopus brain seems to have an entire structure, the vertical lobe, for learning and memory. Inneveration of other areas of the octopus brain seem to impair sensory or motor function, but inneveration or removal of the vertical lobe seems to do nothing until the octopus attempts learning and memory tasks.
This learning and memory can be best seen when
an octopus engages in novel behavior. Octopi are also known for opening
human lobster traps to find food. An octopus is also a notoriously
difficult animal to keep in an aquarium and has been known to switch
tanks in search of food. There have been documented cases of an octopus
throwing rocks against tank glass, and in one instance
short circuiting nearby lighting equipment with water jets. There
is also documentation of tool use (coconut shells as shelter). For
scientists, the octopus allows us to compare complex brains of highly
For a more comprehensive look at the invertabrates, check here.