Blue-lined Octopus
Small but Deadly!
The blue-lined octopus is quite small with an armspan of less than 20cm. It lives in shallow coastal waters, on rocky reefs and around seagrass beds.
The octopus feeds on crustaceans and fish which it catches by injecting its toxin into the animal directly using its beak, or into the water near the animal and waiting for paralysis to occur before eating its prey. The tetrodotoxin causes paralysis by preventing movement of the muscles and diaphragm. The feeding process involves some external digestion, as the prey is broken down by salivary enzymes, before being swallowed.
The bright blue rings and dark blue lines appear when the animal feels threatened and then fade slowly as the threat passes. This is thought to be a warning to would-be attackers that the octopus is poisonous.
Why swim when there's jet propulsion!
The main method of movement used by the octopus is to crawl, using their muscular arms and suckers to anchor them to the bottom. They can also move by jet propulsion. The head of the octopus, the mantle, contains a muscular layer used to circulate water through the mantle cavity. By dilating and contracting the muscular layer opens and closes, forcing water to pass through the funnel. Some of the energy produced by this action is stored until the cavity is refilled with water, and then released as the water is pushed out the funnel, propelling the octopus head-first through the water.
Sensing the surrounding sea
The octopus has a well-developed nervous system that is organised so that peripheral reflex systems are controlled by a central nervous system. The arms of the octopus perform motor functions, such as movement, prey seizure and rejection of unwanted objects, and sensory functions that provde information about their surroundings. Mechanoreceptors and chemoreceptors are located in the rims of the suckers, allowing the octopus to taste and feel potential prey to determine if it is edible. Octopus have large eyes that are almost as efficient as vertebrate eyes, however, they are also colour-blind.
Body, behaviour and breathing
Octopus have the ability to assume a number of different body patterns using colour, texture and posture. These different forms can be used to baffle prey, frighten attackers or pacify companions. The octopus has skin flaps which allow it to change its texture and skin pigments which allow it to change its colour to camouflage itself and escape from predators.
The octopus obtains oxygen by constant water flow across the gills, located in its mantle. At rest, oxygen extraction is about 60%. Activity, such as jet propulsion, reduces the efficiency of oxygen exchange.
Reproduction
The blue-lined octopus mates while the male is carried around on the mantle (head) of the female. The male deposits sperm packages into the body cavity of the female using a specially modified arm. The female plaits her eggs into strings and carries them until they hatch.