The Greater Blue-ringed Octopus (Hapalochlaena lunulata) is one of three (or perhaps four) species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of blue-ringed octopus

Blue-ringed octopus

The blue-ringed octopuses are three octopus species that live in tide pools in the Pacific Ocean, from Japan to Australia . They are currently recognized as one of the world's most venomous marine animals...

es. Unlike its southern brethren, the Blue-lined

Blue-lined Octopus

The Blue-lined Octopus is one of 3 species of Blue-ringed octopuses. It is most commonly found around intertidal rocky shores and coastal waters to a depth of between southern Queensland and southern New South Wales. Its mantle length can grow up to 45 mm...

 and Southern Blue-ringed

Southern Blue-ringed Octopus

The Southern Blue-ringed Octopus is one of 3 species of blue-ringed octopuses. It is most commonly found in tidal rock pools along the south coast of Australia. As an adult, it can grow up to 20 centimeters long and on average weighs 26 grams...

 octopus

Octopus

The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...

es that are found only in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

n waters, the range of the Greater Blue-ringed Octopus spans the tropical

Tropics

The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

 western Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

. Greater Blue-ringed Octopuses can weigh between 10 and 100 grams.

Prey

The Greater Blue-ringed Octopus eats mostly crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s such as crab

Crab

True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s and shrimp

Shrimp

Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

. Also, it eats reef

Coral reef

Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...

 fish that stray too close by. It injects them with a powerful neurotoxin

Neurotoxin

A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

 that easily paralyzes them, which allows the octopus to devour its prey.

Toxicity

Their venom (a poisonous saliva), which includes a neurotoxin

Neurotoxin

A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

 known as tetrodotoxin

Tetrodotoxin

Tetrodotoxin, also known as "tetrodox" and frequently abbreviated as TTX, sometimes colloquially referred to as "zombie powder" by those who practice Vodou, is a potent neurotoxin with no known antidote. There have been successful tests of a possible antidote in mice, but further tests must be...

, is produced by bacteria in the salivary gland

Salivary gland

The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

s. Tetrodotoxin blocks sodium channels, causing motor paralysis and respiratory arrest

Respiratory arrest

Respiratory arrest is the cessation of breathing. It is a medical emergency and it usually is related to or coincides with a cardiac arrest. Causes include opiate overdose, head injury, anaesthesia, tetanus, or drowning...

 within minutes of exposure, leading to cardiac arrest

Cardiac arrest

Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...

 due to a lack of oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

.

External links

• Animal Diversity Web