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Molluscs of Australia

Cephalopods - Octopus

All octpuses have well-developed heads, four pairs of tentacle-like arms, large complex eyes and mouths with hard beak-like jaws. They have no internal or external skeleton, allowing them to squeeze through very small spaces. Octopuses are highly intelligent, probably the most intelligent of all invertebrates.

There are around 300 octopus species, which is over one-third of the total number of known cephalopod species.

Octopuses are found in most regions of the ocean, especially coral reefs. There are two major groups of Octopus - Finned, which have a pair of fins on their mantle, large webs, and small projections (cirri) on their arms. Most species are found in the deep sea and rare and more primitive than the more common Unfinned Octopuses.

Shapeshifting Octopus, amazing camouflage (64 secs)
An amazing video of a camouflaging octopus.

The mantle is a highly muscled structure that houses all of the animal's organs The strong muscles in the mantle protect the organs and help with respiration and contraction.

Digestive gland
Organ producing a secretion that helps digestion.

Shell rudiment
Small internal structure made of calcium carbonate secreted by the mantle; some species do not have shells.

Large sac located where food is held before being digested in the stomach.

Poison Sac
Organ producing venom, which the octopus injects into its prey through its beak.

Bony structure enclosing and protecting the brain.

Anatomy of an Octopus

Main controlling organ of the nervous system.

Buccal Mass
Muscular bulb that contains the beaks, radula, various glands and the pharynx.

A hard mouthpart used for feeding.

An octopus has eight arms used for holding prey and movement.

A funnel, sometimes called a siphon, is a tubular opening that serves as a pathway for water.

Tightly packed muscles on the underside of an arm with a cavity in the centre, Their grip results from reducing the pressure inside the sucker cavity,

Organ which extracts oxygen from water as it flows over it,

Ink Sac
Sac containing an ink-producing gland; when threatened, the octopus releases the ink through the funnel into the water to hide its escape.

Branchial Heart
A muscular enlarged portion of a vein of a cephalopod that contracts and forces the blood into the gills.

An excretory organ that filters wastes from the blood and excretes them and water.

Muscular organ to circulate blood around the body.

Genital gland producingsperm or ova (eggs), depending on the sex of the animal.

Finned octopus swimming (22 secs)
Footage of a young finned octopus of the species Opisthoteuthis agassizii swimming away from the filming vessel.

Next: Biology of Octopuses ...   


Anatomy of Molluscs
The Aplacophora
Tusk Shells
Mollusc Gallery


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