Octopuses can quickly change colour according to background and environmental conditions.
WHILST they feature in children’s stories and are painted on sandcastle buckets, octopuses are very rarely found stranded in rock pools or washed up on the shoreline. Often, friends in Japan, Malaysia, and in Singapore think that they are treating me to an exquisite Asian dish. Recently, in the Camargue area of southern France, where octopuses abound in the Mediterranean Sea, I ate paella for the first time. This ancient, traditional Spanish dish cooked together with spicy rice, fish, shrimps, mussels, vegetables and octopus was delicious. Young and crispy deep fried octopus I can enjoy, but older octopus tastes rubbery and does nothing for my taste buds. In fact, in my memory’s eye, I still see these amazing creatures lithely crawling out of their dens in coral and rocky areas where, in the past, I have snorkelled.
Just over 300 species of octopus have been recorded worldwide in the class of Cephalopoda (literally meaning ‘head footed’). This class includes cuttlefish and squid. The word ‘octopus’ is a relatively recent addition to the English language in the 18th century.
The octopus is the largest and most intelligent of all invertebrates and has been present in our oceans for approximately 325 million years. The oldest fossil found has been dated at 296 million years. This literally ‘eight-footed’ animal is found in various shapes and sizes in temperate, sub-tropical and tropical seas.
Some are found on coral reefs, in pelagic waters and on sea beds, whilst others are located in the intertidal zones and at abyssal depths. They are distinguished from cuttlefish and squid, for these animals have an additional pair of long retractable feet and are referred to as ‘decapods’.
Sizes and shapes
The largest known octopus is the Giant Pacific species (Enteroctopus dofleini) weighing, on average, at 15kg with an arm/foot-span of four metres. Some have been found to weigh in at 272kg with arm/foot-spans of nine metres. This species lives for only two to three years in rocky habitats. The smallest species is the Octopus wolfi, weighing less than one gram and reaching 2.5 centimetres in total length.
The head of an octopus contains its brain, eyes and mouth, as well as sharp, hard beak. It has excellent vision not dissimilar to that a fish. Gills are attached to either side of its head together with a funnel or siphon, which breathes in oxygen, expelling excreta, and used in defence in discharging blue-black ink to blind its predator or providing jet propulsion to escape predators or quickly swim away. The ink is held in a sac under its digestive system. Its outer, thin epidermis allows it to lengthen, contract, and change its shape according to circumstance.
Its feet are connected to its head by a web-like structure of thin skin. The muscular legs hold adhesive suckers, allowing the octopus to wriggle freely in any direction. These suckers allow it to feel around coral or rocky structures or to taste its food before eating. Whist each leg has a central nerve connection to its brain, they can work independently from the brain. It boasts three hearts; one that circulates blood around its body while the other two pump blood around its gills. Its main heart forces the octopus to tire and take rests when swimming. If only we mere mortals had such devices!
The Dumbo octopus is found in the deepest waters of our oceans.
Birth and thereafter
Male octopuses have a special arm that they use, under the right conditions of temperature and light, to remove their sperm and to invade a female’s oviduct. Eggs are then laid by the female octopus in strings, which are attached to sheltered areas or rocks or coral overhangs. She will guard them until they hatch, in the case of the Giant Pacific octopus for over 150 days.
Once the eggs have hatched, the female dies almost immediately. Her male partner would have died shortly after mating when he rapidly aged. Thus adult life expectancies are relatively short. The hatchlings feed on copepods and other zooplankton.
Feeding habits
Their main diet varies from species to species, from crustaceans, molluscs, prawns, fish, crabs and spider crabs, all of which they inject with their paralysing saliva before first breaking them up with their beaks or by drilling shells open with their small teeth. Shells can easily be dissolved by a saliva injection.
They venture from their dens by crawling towards their prey, by swimming backwards or head first, or by ‘jet propulsion’. The latter is caused by a sudden expulsion of water through their siphons.
The Giant Pacific octopus has been found to weigh up to 272kg.
Camouflage
These ‘chameleons’ of the sea can quickly change colour according to background and environmental conditions, be they coloured coral, rocky outcrops or through fear of predators. Their skin cells contain black, brown, orange and red pigments, which can be released in multi-coloured combinations across their whole bodies. Often, when mating, their colourings change to attract or communicate with a partner.
Solitary or not?
In 2006, researchers recorded that only three species could tolerate each other’s company. More recently, off the coast of New South Wales in Australia, at Jervis Bay, an octopus city was discovered with a 13-roomed complex on a rocky outcrop 10 metres below sea level.
Its occupants are the species Octopus tetricus, who take home their prey, dropping the cast off food around their burrows, which duly attracts further shellfish to scavenge and thus provide the octopuses with their next meal. There is more to discover of their behaviour at ‘Octopolis’!
In the darker abyssal zones of the oceans, at depths of between 1,000 and 3,000 metres, solitary Dumbo octopuses have been found. This species has been so named, for it possesses fins which look more like flapping ears reminiscent of Walt Disney’s cartoon elephant. These creatures feed on tube worms at hydrothermal sulphuric volcanic vents in the seafloor. The skin flaps on their fins and above their eyes, allow them to hover above the seabed.
The blue-ringed octopus is truly venomous.
Humans and octopuses
All octopuses are venomous, only biting when provoked or stepped upon, leaving, in most cases, temporary paralysis and short-lived swellings on the human body. However, in the ‘Coral Triangle’, covering 6.8 million square kilometres of ocean to include eastern Bornean shores, the world’s most venomous creature lives – the Blue ringed octopus. Beware when snorkelling. This is the only species of octopus that has a venom lethal to humans and may cause death through respiratory problems.
Octopus ‘fishing’ is widespread in the Mediterranean Sea and throughout South East Asia. Caught by baited pots, trawl and drift nets, snaring, hooking and spearing methods it is a big source of income for local fishermen and restaurant businesses.
Apparently, octopuses have a food conversion greater than that of chicken.
Obviously, the very deepest oceanic waters are still relatively unexploited by man but in pelagic waters, the UK took the lead in 1986 in protecting the common octopus (Octopus vulgaris). It took a European Union directive another six years later to extend this order to protect all cephalopods.
Was the octopus I ate in the paella dish in France imported? I don’t think so! If you are ever snorkelling or diving off the eastern coasts of Sabah or Kalimantan, do beware of the blue ringed octopus.