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Octopus and squid

by  Maggy Wassilieff and Steve O’Shea

Octopus and squid are fascinating creatures rarely seen and still a mystery to those who study them. Glimpses have been afforded in New Zealand. The internal, spiral shells of tiny ram’s horn squid are a common sight on west coast beaches. And a colossal squid, thought to grow to 15 metres, was brought up from the deep waters in the south.


Head-footed animals

Octopus and squid represent the pinnacle of invertebrate evolution: they are the most intelligent, and contain some of the largest, heaviest and most aggressive of the invertebrates (animals without backbones).

How to tell a squid from an octopus

A popular misconception is that squid have eight arms and two long tentacles, while octopus have eight arms and no tentacles. But this is not always the case. The only real difference between the two groups is that squid have hooked or saw-like suckers, and octopus do not.

Classification

Octopus and squid belong to a group of marine invertebrates known as cephalopods. Cephalopod means ‘head-footed’ – the arms and tentacles are derived from the head. Their closest relatives are snails, slugs, chitons and shellfish, collectively known as molluscs. Cephalopods have a long fossil history and include extinct groups such as the ammonites and belemnites, both of which have been found as fossils in New Zealand.

Of the five surviving orders (major groups), four are represented in New Zealand: cuttlefish, squid, octopus and vampire squid. The group to which pearly or chambered Nautilus belong are absent from New Zealand waters, although their empty shells occasionally arrive on northern beaches, swept down from the Pacific on ocean currents.

Octopus and squid bodies

All species of octopus and squid have a mantle, head and eight arms (and in the case of some squid, two additional tentacles).

  • The mantle is a tapered or cylindrical sac containing the organs. Most squid and some primitive octopus have an internal shell within their mantle. A few cephalopod species (true nautilus and the female paper nautilus) secrete external shells. Squid and some octopus also have fins at or near the rear of their bodies, which assist with movement through the water.
  • The head contains the brain, two eyes, a mouth with a beak like a parrot’s and, attached to the underneath surface, a muscular funnel. When water is forced out of the funnel, the animal is propelled in the opposite direction.
  • Both octopus and squid have eight arms encircling their mouths. Most octopus have suckers on the insides of their arms. Squid suckers are armed with a variety of hooks and claws. All squid possess two long tentacles at some stage of their life.

Techniques for disguise

The bodies of octopus and squid are covered in chromatophores – tiny contracting and expanding pockets of pigment that cause instantaneous colour change. They have the ability to change from solid red to completely transparent in a millisecond. Octopus can alter the texture and colour of their skin to perfectly match the surrounding seabed.

Ocean-dwelling squid and a few octopus species have light-producing (bioluminescent) organs that are used for counter-illumination, masking the animal’s silhouette against the bright light from above.

Most octopus and squid species can squirt out a cloud of ink from their mantle when disturbed. The ink is thought to function as a decoy to confuse predators. Some deep-sea species release luminescent ink.


Life history

How octopus mate

The third arm of many male octopus species is specially modified for transferring packets of sperm (spermatophores) to the female. During mating the male inserts his modified arm into the female’s mantle. Sperm packets are released through his funnel into a groove on his modified arm, from where they are guided to the female’s reproductive organs.

Some open-ocean octopus have a unique form of reproduction. This is true of the paper nautilus (these are not true nautilus, but a species of octopus named because their shell appears similar to that of a Nautiloid). The tiny male’s modified arm breaks off during mating, and through some unknown process navigates its way into the female mantle cavity, taking residence around her gills and eventually releasing its sperm. Males are assumed to die after mating. The blanket octopus (Tremoctopus violaceus), known from the Tasman Sea, exhibits the most extreme form of sexual size difference, with females being 40,000 times heavier than males.

How squid mate

One or more arms of many squid species is modified for reproduction, transferring a sperm packet to females in a similar way to octopus. For those squid species lacking modified reproductive arms, the male often has a grossly enlarged penis that it uses like a giant syringe to thrust spermatophores into various parts of the female’s mantle, head or arms. Male scaled squids (Lepidoteuthis grimaldii) also possess two sabre-like hooks, which they stab into the larger, slippery females during mating.

Egg development

Most octopus species deposit eggs directly onto the sea floor, but some open-ocean species brood their eggs in their mantle or around their mouth. The shell of the paper nautilus is really an egg case and brood chamber, secreted only by the female and in which she lays her eggs. Shallow-water species generally produce many small eggs that develop into hundreds, if not thousands of tiny plankton-feeding young. Deep-sea species produce fewer, larger eggs, and their young hatch and commence life as miniature adults, crawling around the sea floor.

Most squid release large, free-floating gelatinous egg masses – up to 2 metres in diameter in the case of arrow squid (Nototodarus gouldi) – each containing thousands of eggs. A few species discharge tiny, individual eggs. Females of some deep-sea squid species brood their eggs in their arms. The coastal-dwelling broad squid (Sepioteuthis australis) attaches strands of white, grape-like eggs to seaweed.

Squid rings

Scientists count the rings on two tiny skull bones (statoliths) in a squid’s head to determine its age. Some shallow-water species deposit these rings on a daily basis, but it is not certain whether the same applies for deeper-water species. If it does, then giant squid (Architeuthis) would be only 480 days old – a staggering growth rate, given that this squid hatches from an egg only 2 millimetres in diameter and grows to 13 metres in length.

The majority of squid and octopus hatch as miniature adults. Several exceptional squid species have a larval stage that undergoes a distinct metamorphosis to the adult form.

Growth

As squid have proven exceptionally difficult to keep in captivity, studies of longevity are extremely rare. Most octopus and squid species are thought to live for only a single year, and die after mating.


Feeding and predation

Octopus and squid are predatory animals with highly developed senses to help them detect food. They cannot eat their prey whole. Food enters a narrow oesophagus that passes directly through their doughnut-shaped brain.

How octopus feed

Octopus seek their prey using acute visual or tactile cues. They restrain an animal with their suckers, engulf it in an intertwined mass of arms, and draw it close to them. Most octopus and cuttlefish bite their prey and inject it with paralysing saliva. Before swallowing, they dismember the animal into bite-sized pieces with their sharp beaks.

The diet of bottom-dwelling octopus species is mainly molluscs (particularly whelks and clams), crustaceans (mostly crabs), and polychaete worms. Open-ocean octopus and squid eat mainly fish, prawns, and other cephalopods.

How squid feed

Squid species catch prey in a variety of ways. Many of those with tentacles shoot them out towards their prey, drawing the struggling animal into its arms to be dismembered. Some squid with exceptionally long tentacles drag them over the seabed, capturing small prey in myriad minute, sticky suckers, then slowly withdrawing the tentacles to the arms. Others dangle their long tentacles down into a school of fish, squid or prawns, clasping hold of one and lunging forward to restrain the prey with their arms.

Those species of squid that lack tentacles have suckers endowed with an arsenal of hooks. They simply lunge at prey, restraining it with their short, muscular, hooked arms.

Predators

Octopus and squid are the staple food, or are important in the diet of many fish, bird and mammal species. Most notably these include orange roughy fish, wandering albatrosses, and sperm and pygmy sperm whales.


Octopus in New Zealand

Coastal species

Of the 42 species of octopus known from New Zealand, only a few are commonly encountered. Octopus live mainly on the sea floor. However, small specimens of the common octopus (Pinnoctopus cordiformis or wheke) and the fist-sized Octopus huttoni can often be found in tidal rock pools. As wheke grow, they venture into subtidal reefs. Reaching over 1 metre in length and 9 kilograms in weight, they are among the largest predators on the reef. They feed on crayfish, crabs and shellfish.

Octopus in proverb

Māori refer to octopus in their proverbs. One draws upon the animal’s tenacious nature when hiding among rocks: ‘Etia me te wheke e pupuru ana’ (holding on like an octopus).

Another is scornful of the way octopus, if caught, give up without a fight: ‘Kia kaua e mate ā-wheke, me mate ururoa’ (do not die like the octopus, rather die fighting like the great white shark).

Ocean dwellers

Paper nautilus (Argonauta nodosa and Argonauta argo) are found in surface waters of the open seas around New Zealand. They are known for their delicate shell, formed by the female as a brood chamber for her eggs. In early summer, females move to coastal waters to release the shells containing their developing young. The empty shells are often washed up on New Zealand’s north-eastern beaches.

Giants

Two of the world’s largest species of octopus have been found around New Zealand:

  • An incomplete specimen of the giant gelatinous octopus (Haliphron atlanticus), which grows to 4 metres in length and weighs 70 kilograms, was trawled from a depth of 920 metres near the Chatham Islands.
  • The giant South Pacific octopus (Enteroctopus zealandicus), which reaches 3 metres and weighs 30 kilograms, has been identified from beaks found in the gut of beached whales.

Māori and octopus

According to legend, the Polynesian navigator Kupe was led to New Zealand by the giant octopus Te Wheke-o-Muturangi. Intent on killing the octopus that was robbing his tribe of fish, Kupe, along with his family and some warriors, set out in a large canoe to hunt it down. The octopus swam south for weeks and eventually took shelter near Cook Strait, where Kupe found it. After a ferocious battle, Kupe tricked the octopus into wrapping its arms around some water containers, and killed it with a blow to the head.

Māori caught octopus by hand. They placed one hand into the water to act as bait and when an octopus wrapped its tentacles around their arm, they seized the body with their other hand and hauled the animal out of the water.


Squid in New Zealand

New Zealand has a rich and diverse assemblage of squid and related groups, with more than 85 species.

Distribution

Most squid are open-sea animals, although a few, like cuttlefish, spend their lives mainly on the sea floor. The vampire squid (Vampyroteuthis infernalis) has been collected throughout the depths of the ocean and close to the seabed. The tiny ram’s horn squid (Spirula spirula) has an internal, coiled shell for buoyancy, allowing it to move up and down in the water with very little effort. Although they live far from shore, their presence in New Zealand waters is evident from the quantities of empty shells that wash ashore following their death after breeding.

Giant squid

Adult giant squid (Architeuthis dux) come to breed in deep waters around New Zealand. Females grow to 13 metres from tail to tentacle tip, and can weigh 300 kilograms. Their huge eyes – about 30 centimetres across – are designed to pick up flashes of light from fish and smaller squid. It was once thought that they were fearsome hunters, but based on their weak musculature, it is likely that they wait in the depths for passing prey.

In 1879, Thomas Kirk vividly described a washed-up giant squid: ‘the beast had eight tentacles, as thick as a man’s leg at the roots; horrid suckers on the inside of them; two horrid goggle eyes; and a powerful beak between the roots of the arms. His head appeared to slip in and out of a sheath. Altogether he was a most repulsive-looking brute. … All the natives turned out to see him … they say that these large “whekes” are very apt to seize a man and tear his inside out.’ 1

Giant squid in Kaikōura canyon

A massive submarine canyon extending out into the ocean, just south of Kaikōura, is the legendary home of a monster squid named Whakatere. This tradition may have some basis in truth, for giant squid larvae have been found in waters off the east coast of the South Island, although live adults remain elusive.

Colossal squid

Larger and more fearsome-looking than giant squid, colossal squid (Mesonychoteuthis hamiltoni) may frequent New Zealand’s southern waters. One juvenile was captured in 2003 off Macquarie Island, 900 kilometres south of New Zealand. This animal is estimated to reach 15 metres in length, but as no adult has yet been caught this figure has still to be confirmed. The colossal squid’s body shape and swivel-hooked suckers suggest that it is a powerful predator.

Further discoveries?

Cephalopods are known around New Zealand to depths of 3,150 metres. However, New Zealand’s waters reach depths of more than 9,000 metres, and have been only poorly sampled. Undoubtedly, many deep-sea species, possibly including squid, await discovery. However, despite the importance of these animals in marine food webs, their diversity, and the fascination they hold for humans, very little is known of their biology. Several recently discovered cephalopods are near to extinction.

Footnotes
  1. T. W. Kirk. ‘On the occurrence of a giant cuttlefish on the New Zealand coast.’ In Transactions of the New Zealand Institute 12 (1879), p. 311. › Back

Squid fishing

Japanese boats began fishing for squid in New Zealand waters in 1969. New Zealand fishermen took up squid fishing a decade or so later, employing, at first, jigging techniques learnt from the Japanese. Jigging happens at night, when squid are lured to surface waters by powerful lights hung from boats, and are caught on spinning multi-barbed hooks attached to long lines. Most squid are now caught by trawling.

Squid fishery

The New Zealand squid fishery is based on two closely related species of arrow squid (Nototodarus gouldi and Nototodarus sloanii). Both live for a year, growing rapidly to about 30 centimetres in length and just over 1 kilogram in weight. The fishery is concentrated around the South Island and the subantarctic Auckland Islands, and runs from February to May. The catch is highly variable, depending upon the survival rate of juvenile squid. Most of the squid is frozen and exported worldwide. Earnings were $86 million in 2002.

Squid on the plate

Few New Zealanders ate squid before the 1980s, and those who did were likely to have come from Italy or Greece, where calamari (squid) are part of a long culinary history. The tentacles, mantle or tube and fins are all edible, and may be cooked in a variety of ways. Whole tubes can be stuffed and baked, or cut into rings, which are then crumbed and fried. Tentacles and fins are suitable for stir fries. Squid flesh takes only a few minutes to cook, changing from translucent ivory to opaque, milky white. It has a delicate shellfish taste, but becomes rubbery and unpalatable if overcooked.


External links and sources

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How to cite this page: Maggy Wassilieff and Steve O’Shea, 'Octopus and squid', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/octopus-and-squid/print (accessed 21 April 2019)

Story by Maggy Wassilieff and Steve O’Shea, published 12 Jun 2006