Found hiding under rocks and in shells along beaches from Japan to Australia, the blue ringed octopus, Hapalochlaena lunulata, is one of the most beautiful creatures in the waters; but, it’s appearance can be deceiving as it is also one of the most deadly octopuses in the world.
Photo from CirclesOfLight via Flickr
These small octopuses are only the size of a golf ball but their bite contains a strong neurotoxin with the ability to be fatal to an adult human. When resting, they appear yellow in colour with brown spots; however, when provoked, they exhibit about 60 bright blue rings that cover their body.
Most octopuses utilize three structures when demonstrating colour change of their skin: chromatophores, iridophores and leucophores. Chromatophores are sacs in the skin, filled with pigment and controlled by the surrounding muscles. Upon contraction or relaxation, the sacs shrink or expand to change the look of the pigment. Iridophores are iridescent sheets located beneath chromatophores that are controlled by the shift of proteins and cytoplasm. This results in the sheets reflecting different wavelengths of light or UV rays to change the sheet’s appearance. Lastly, residing under iridophores, leucophores reflect white light to give contrast to the other colours from the chromatophores and iridophores.
Photo from Steve Childs via Flickr
Recently, researchers have found that this typical method of visual display is not how the blue ringed octopus warns its prey. The rings on this small octopus are made of iridophores with no chromatophores above them; instead, the chromatophores were located beneath and surrounding the rings. To give its warning, the octopus relaxes the muscles above its rings and contracts the ones surrounding it, exposing the iridescent blue of the iridophores and dark pigments of the chromatophores. With the iridophores on clear display and chromatophores surrounding, the blue ringed octopus is able to employ an impressive and vivid warning signal as seen below:
As impressive as this display is, it is also very effective. The blue-green section of the visible spectrum is seen by most of the predators interested in eating these octopuses and it is vivid in underwater light. The speed at which the display is activated combined with the bright colour proves beneficial for both predator and prey as the predator is warned before it attacks the deadly octopus and the octopus survives to live another day.
The defensive nature of this small creature just goes to show that appearances can be deceiving – even the most beautiful of creatures can be deadly.
– Karly Stillwell
