Many people, especially divers, are surprised to learn that octopuses are very commonly encountered on our shores. These marvellous creatures are a delight to observe, but need patience and some experience to spot.
These masters of camouflage are shy and generally only active at night. During the day, they are often well hidden in some cosy den. Some octopuses seen are as large as 1m across with their arms outstretched. Others are tiny, less than 10cm across.
Octopuses are generally more common in areas with coral rubble, but may also be seen in seagrass areas, like this octopus seen on Changi.Awesome Octopus
The octopus is a hunter with many tricks. Among its formidable weapons is its brain! The octopus is in fact considered the smartest known invertebrate. It has a well-developed brain and excellent eyesight. Studies show that the octopus can learn, not only by itself but also from one another!
Armed and Dangerous
An octopus searches for prey mostly at night, spreading out its eight long arms to feel into crevices for crabs, prawns, snails, clams and other such morsels. The highly flexible arms have strong suckers to grip objects so that the octopus can slowly 'creep' over the surface as it stealthily investigates all hiding places (octopuses use jet propulsion when they are in a bigger hurry, see below). The arms also have numerous receptors sensitive to taste and touch.The arms are joined together near the head with webbing. An octopus uses this webbing like a net. For example, to envelope a little mound of rubble where some small titbit might be hiding. When the prey attempts to escape, it is literally surrounded by octopus!
Shell-less but not helpless
The octopus is a mollusc like snails and clams. But the octopus does not have a shell at all. This is actually an advantage as the octopus can then squeeze into all kinds of impossibly tight hiding places.
The octopus also has many other ways to deal with danger.
In the first place, an octopus is generally very difficult to spot. It can change its colours and even the texture of its skin to blend with its surroundings. And change these rapidly as it moves to a new location.
These pairs of photos are of the same octopus changing colours ...and patterns ...almost instantly too!This one on Sisters Island can't decide what colour it wants to be!Octopuses also have other tricks up their many arms. This octopus was observed on Chek Jawa swimming with all its arms arranged so that it resembled a flatfish.When spotted, some octopuses make sudden drastic colour changes to confuse the predator. They then zoom off using jet-propulsion; squirting a jet of water out of a funnel to slide off in the opposite direction. When particularly alarmed, an octopus may release a cloud of ink to disorient predators. The ink may contain substances that affect the senses of other sea creatures. In the clouded water, the octopus makes its getaway.
Octopus in love
Octopuses have separate genders. The male has a special arm called a hectocotylus that is used to insert a sperm packet into the female's body.
This pale male on Sentosa is keep his distance as he does his thing with a larger female. The female uses the sperm to fertilise her eggs as she lays them. In most octopus species, the eggs are laid in capsules attached to hard surfaces.
Octopus for lunch
Many marine creatures love to eat octopus. But first, they got to catch them. Then deal with eight furious arms.
So the next time you visit a shore or reef, look closely for this incredible animal and patiently observe it as it goes about its daily life.
Links to more octopus
photos of octopuses on wildsingapore flickr