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Hapalochlaena fasciata  (Blue-ringed octopus)


Phylum: Mollusca
Class: Cephalopoda
Family: Octopoda
Family: Octopodidae

Geographic Range

Physical Characteristics

Diameter:4-6 cm
Length:20 cm
Mass:28 grams (1 oz.)
The blue-ringed octopus has a soft sack-like body with a base skin color ranging from dark brown as in the picture above to dark yellow. Faint blue rings can be seen across the entire body including the eight arms that extend from it. These arms are also covered with suckers. When the octopus becomes irritated these blue-rings light up to an irridescent blue that is very attractive to look at but deadly to touch.

Natural History


The breeding season for the blue-ringed octopus is late Autumn. The female initiates mating by indicating her fertility through body coloring and body posture. The male then approaches her for courtship which may or may not include "love play" and caressing. The male has evolved a modified third arm, called the hectocotylus, that he uses to inseminate the female. Elongated spermatophores are sent along a groove running the length of the edge of this modified arm to a leaf-shaped grasping structure at the tip of the arm where it is then inserted into the oviduct of the female. It is possible for the female to store the sperm for up to three months if her eggs are not mature at the time of insemination. After insemination the male dies. The female lays roughly fifty eggs and cares for/guards them for the next three to six months until they hatch. This is called the brooding period. When the eggs hatch the female dies. Eggs hatch into planktonic "paralarva" which are only 4 mm long (the size of a pea). They float to the surface of the water and join the plankton while they rapidly develop. After a month they return to the bottom of the water where they continue to mature until the following Autumn when they are ready to reproduce.


The blue-ringed octopus makes its home in shallow waters where the habitat is sandy or muddy. They can often be found lurking under rocks in search of food especially after storms that wash up new food into rocks pools, tide pools and shallow coral outcrops.


Economic Benefits for Humans


The venom of the blue-ringed octopus is currently being studied for possible medicinal uses.


This invertebrate is VERY poisonness and an attack by it may result in death. This is not so much a problem for adults that may be more aware of the dangers of the blue-ringed octopus but it is a serious concern for children who are immediately attracted by the bright colors. In addition there are no known antidotes to the venom of the blue-ringed octopus. Currently the only treatment for the paralysis induced by the blue-ringed octopus is CPR which must be performed continuously until the poison has left the body of the victim. This could take up to twenty-four hours in severe cases. By that time the victim will no longer be subject to paralysis and will be able to breath on their own again.

Image Source

Reference: Blue-Ringed Octopus

Reference URL: http://www.aqua.org/images/brocto.jpeg

Entry Author: Missy Knox William Smith College 2002

Hobart & William Smith Colleges and Union College
Partnership for Global Education: Queensland Term 2001