Octopuses are a group of cephalopods known for their intelligence, their uncanny ability to blend into their surroundings and the rather unique way they get around (jet propulsion). In this article we'll explore what makes octopuses unique and we'll find that there's more to octopi than eight arms.
FACT: There are two groups of octopuses alive today.
There are about 300 species of octopuses (Octopoda) alive today. Theses species are are divided into two groups, the Cirrina and the Incirrina.
The Cirrina (also known as the finned, deep-sea octopuses) are characterized by having two fins on their head and a small internal shell. They also have cirri, small cilia-like filaments on their arms (there is a pair of cirri adjacent to each sucker on the arm; these structures may have a role in feeding).
The Incirrina (the benthic octopuses and argonauts) include many of the better-known species of octopuses, most of which are bottom-dwelling species. The Incirrina also includes the pelagic argonauts.
FACT: Octopi have arms, not tentacles.
It is a common mistake to refer to an octopus' arms as tentacles. Tentacles are longer than arms. Tentacles usually have suckers only at their tips.
FACT: Octopi squirt ink to defend themselves.
Most species of octopusi can release a thick cloud of black ink that helps to confuse predators and provide the octopus an edge when attempting to escape. One of the pigments in the octopus' ink is melanin (the same pigment that gives our skin and hair color).
FACT: Special skin cells called chromatophores enable octopi to blend into their background.
Chromatophores enable an octopus to camouflage itself with its surroundings by changing the appearance of its epidermis.
FACT: There are three plural forms of the word octopus.
They include octopi, optopuses, and octopodes.
FACT: Octopi are cephalopods.
Cephalopods are a class of mollusc that includes squids, cuttlefish, nautilus, and octopi. Cephalopods are bilaterally symmetrical and have a head, arms, and in some cases, tentacles.
FACT: An octopus has three hearts.
Two hearts are used to pump blood to each of the octopus' lungs and the third pumps blood throughout the body.
FACT: Octopi have short lifespans.
Their lifespans vary among species but can be between six months and five years.
FACT: Octopi are highly intelligent.
They are believed to be the smartest of all invertebrates and show great skill at problem solving (instead of relying on instincts).
FACT: Octopi can fit into small crevaces.
Since they have no internal or external shell or bones, they can manipulate their body to fit into tight spots.
FACT: Octopi move through the water either by crawling or by jet propulsion.
Octopuses are among the few animals that move by means of jet propulsion. Because jet propulsion requires much energy, many octopuses also crawl when moving more slowly. If an octopus needs to get away in a hurry, it uses jet propulsion by contracting their mantle and expelling a jet of water that propels them forward.