the octopus, smart and handy by Dr Floor Anthoni www.seafriends.org.nz/indepth/octopus.htm
Inkfishes (cephalopods) are fascinating creatures of the oceans
because they have evolved from a very distant past, into forms that have
many arms, excellent eye sight, an acute sense of smell and well developed
brains. Today they are thought of as molluscs (soft-bodied) even though
they do not resemble any of the typical molluscs of today, such as shells,
clams and nudibranchs. In this article we'll have a close look at the most
common shallow water inkfishes of New Zealand, in particular the brainy
and handy octopus.
An old heritage It is thought that the inkfishes (cephalopods) originated from
early gastropods (slugs and snails) some 500 million years ago in
the Ordovician epoch of the Palaeozoic (see our Geologic
time table). Their ancestor looked a bit like a large limpet, but with
its internal organs in a different arrangement. Its head developed tentacles
and its foot formed the funnel (jet pipe). Its mantle developed into a
bag in which the gills are located and also its anus and sexual organs.
Its external shell first developed into a cone, still worn by belemnites
that became extinct with the dinosaurs.
Separate from this, some 400 million years ago, ammonoids and nautiloids
developed with chambered coiled shells. Some fossil ammonoid shells (ammonites)
were indeed quite big, up to one metre across! Today the only live inkfish
wit an external shell is the Nautilus. All others have internal
remnants of shells. (The ramshorn has a chambered internal shell)
How cephalopods could have evolved from early gastropods.
Early gastropods (stomach-foot) of 600 million years ago had their gills
at the rear of their bodies, rather than in front, as present gastropods
have. Their heads developed tentacles, hence the name cephalopod (head-footed).
The foot became a funnel (pipe). Early cephalopods had horn-shaped shells
that eventually developed gas chambers to counteract their weight. This
development led to the ammonites, belemnites and nautiloids. Squid and
sepia developed streamlined long bodies with an internal shell and suckers
on their arms. They also developed an extra pair of arms for catching prey
with. Gills became larger for sustained swimming. Octopuses lost their
shell and developed massive arms and a squat body.
Today's cephalopods are as varied as all other molluscs combined, even
though they are not represented by as many species (marine molluscs 90,000;
cephalopods 900). All cephalopods occur in the sea only and all are predators.
The drawing below shows how varied they are.
Cephalopods are such weird creatures that their classification
has been in constant revision, and is likely to be revised yet again. One
would have thought that squid can be distinguished from octopus because
they have ten arms instead of eight. However, the way inkfish have been
grouped today, squid are those inkfish with hard hooks or saw-like cups
around their suckers, whereas octopuses have soft stalked suckers. (See
octopus biology There are about 300 species of octopus (Gk: oktapous= eight
feet), among the nearly 900 species of inkfish. As its name suggests, an
octopus has eight highly developed arms with which it can capture prey,
manipulate food and walk around on. Between its arms it has a tough skin
(web) which it can use as a catch bag for catching prey in. An octopus
has no bones and is entirely soft-bodied apart from some cartilage in its
'skull'. Because of this, an octopus can squeeze itself through small holes,
a little larger than its eye.
about ±300 species
Order: Octopoda, the octopuses
with eight arms
An octopus is not streamlined for swimming, like squid, but rather squat
and more suitable for living in small quarters and crawling over rocks.
An octopus has a powerful jet pipe which serves for exhaling, and as jet
propulsion for swimming fast. Some octopus species do not live on the bottom
but swim in the open sea. Like all other cephalopods, octopuses grow fast
and do not live long (1-2 years).
octopus biology The
diagram shows in simplified form what is inside and octopus. It has a horny
parrot beak with strong muscles, enabling it to slice through its prey
rapidly. In its mouth it has a radula with which it can scrape and chew,
assisted by secretions from its salivary gland (and stomach) which often
contains poisons to stun prey and attackers. Molluscs that live from clams,
can in short time penetrate their shells and paralyse them. Not far from
the mouth an octopus has a crop to store excess food. From there the food
enters the alimentary canal (guts) to the stomach and further to exit from
its anus. The anus is conveniently located before its funnel, such that
its wastes (a long thin string) can be jetted out of the hole where it
lives. There is also its ink sac which can be emptied rapidly as a black
Octopuses have large livers and kidneys to excrete wastes. Its gonads
are located in the back of its body, but males have quite different sexual
organs compared to females. Sperm passes through a spermatophore packing
chamber before being ejected from the penis. Females have similarly a production
chamber for making large eggs. They also have receptacles for the male
The mantle (bag) leaves quite a large space for breathing. By opening
the mantle, water is breathed in and passed over the gills and, by squeezing
the bag, out through the funnel, in a smooth movement. Contrary to most
other water breathers, an octopus reverses the flow of the water, which
is rather energy-inefficient. However, as part of its jet propulsion method,
a squid can swim fast over long distances while aerating its gills faster
as it swims faster.
f960210: the parrot beak of an octopus has been removed and
its radula, a soft 'tongue', pulled out. Through this tongue an octopus
can excrete acids or poisons. The sand octopus drills holes in shells with
its stomach acids that dissolve the limestone. By practice, it learns precisely
to drill the hole where the shell's adductor muscles are. Notice the two
other places where it tried.
f015902: the suckers on the eight arms become smaller and
smaller towards its mouth, shown in the centre. With these fine suckers
an octopus manipulates fine food particles. Females use them for stringing
their eggs together, very precisely. Notice that the 'lips' close over
f039933: a large octopus dominates its environment as a fierce
predator, and the big ones do not show much fear. They can walk straight
up to the photographer to admire all the shiny bits on his camera.
f039934: a large octopus breathing out through its jet pipe.
Notice the body bag on right and the orange flap to seal it against the
jet pipe. (Octopus gibbsi)
sharp eyes Not many inkfishes have well developed eyes. The nautilus for example
has a little pinhole which works much the same as a pinhole camera (not
sharp while not sensitive to light either). Squid have large round eyes,
particularly the deepwater giant squid, which are light sensitive but do
not afford any detail. In general, those inkfish living in shallow well-lit
waters, have developed good eyes, and octopuses indeed have very good eyes.
They even have eye lids that allow them to squint and adjust to available
light. From behavioural experiments, scientists think that octopus cannot
distinguish colours but can distinguish brightness, size, orientation and
form. But how then do they manage to mimic the colours of their environment
f039515: a super closeup of a young octopus shows its skin
structure and the individual colour cells (chromatophores) that enable
it to change colour. An octopus is one of the few lower animals able to
close its eyes (or is it the only one?).
f039516: An octopus has eye lids which it can close. Here
it is squinting in the camera's modelling light. Between its eyes is its
brain. Polynesian skindivers who catch octopus and then quickly need to
kill it, bite it between the eyes to crush its brain.
In our aquariums we had a special tank for an octopus
- a prison really. A new octopus would hide in the farthest corners, but
once it lost its fears, it would always hang around right in front, watching
the goings-on in the other tanks. In other words, with its mind it lived
in the whole tank room, being quite aware of other objects and even prey
moving in far away tanks.
masters of camouflage Inkfishes can change their skin colours rapidly because they have skin
cells with various colours, and can vary the sizes of these. Like a colour
TV set, they have three layers of chromatophores with different base colours:
black-brown, red-orange, orange-yellow. Each chromatophore can widen or
shrink in size, thereby varying the intensity of its colour. Underneath
the chromatophore layer are iridophores in the colours pink, yellow, green,
blue, sliver and behind that is an opaque reflective layer of pure pearly
white. Truly a photographer's dream of the ideal colour printing paper,
except that the base colours do not match our eyes: cyan, magenta, yellow,
Schematic diagram of the skin of an octopus: The epidermis
(top skin) protects the underlying skin and is totally transparent. Directly
underneath are three layers of chromatophores with colours depending on
each octopus species. Each chromatophore is surrounded by a ring of muscles,
of which only eight are shown above. These small muscles open and close
the colour cell under control of the nervous system. The three layers act
independently, much like in a colour TV set. Underneath the colour cells
is a layer of iridophores that produce a metallic sheen in the colours
blue to pink to silver, also depending on species. Underneath is a pearly
white reflecting layer that, by reflecting the light, amplifies the effect
of all layers above it. Then finally there is a layer of muscles that can
change the texture and look of the skin. In all, this is totally amazing
and not found in any other mollusc or any other animal for that matter.
Of all cephalopods, the sepia (the Mediterranean sepia is Sepia officinalis)
is the most amazing skin painter. Alas it does not occur in New Zealand.
A sepia can change its colours so rapidly that it can mimic the rolling
patterns of waves. When mating, it sports gaudy zebra patterns. A young
sepia can literally disappear before one's eyes, no matter where.
f009133: octopus are experts in camouflage, able to change
their skin colour and texture to match the environment. Can you spot this
f040308: in the centre of the picture sits an octopus. Can
you see it? Where are its eyes?
regenerating arms Up to a point, an octopus can regenerate lost arms. Quite often the
tips of its arms are bitten off by fish with sharp teeth or by the odd
crab defending itself, reason why it is often seen defensively curling
up the tips of its arms. But when fishermen cut some legs off an octopus
for use as bait, then discarding its body, the stumps cannot regrow. Male
octopuses have one arm that is more important than all others, its mating
arm (see octopus sex below). This arm is not used as often as the others,
and it is kept hidden much of the time. It does not take part in exploring
its surroundings either.
Every arm has fine taste buds with which the animal tastes its environment
while crawling along. One of its arms does the scouting and when prey is
detected, the octopus suddenly jumps forward, spreading its web wide to
catch any escapees. It is a method that guarantees success. Think of an
octopus as a walking catchbag.
f015904: an octopus can regrow the tips of its arms in case
these are lost in a fight or bitten off by predatory fish.
f960205: when dead and preserved, octopus species become
difficult to distinguish but males have a special mating arm (the third
on their right sides) which has a groove running along its entire length
and a special tip to collect and deposit sperm packages (hectocotyl). This
photo shows the tips of the reef octopus and that of the sand octopus.
f010737: an octopus has lost four of its most important frontal
arms but can still survive.
arms or legs? The name of the octopus says it all: eight feet. But
these feet did not originate from the foot of the original limpet it evolved
from. That foot developed into the octopus' funnel or jet pipe, whereas
the eight feet of the octopus developed from mouth flaps, reason why they
are attached to the head rather than the belly, and that they surround
the mouth without leaving a gap. We have no word for such tentacles.
When one observes a living octopus, one sees immediately that its feet
are not made for walking on, because they are floppy. In fact, these feet
are enormously flexible and even more than hands, suitable for holding
objects, which is precisely what octopuses use them for. So there is no
doubt that the octopus' feet work more like arms and hands than legs and
feet. We're thus quite happy to call them arms, however, they are
they are strong and robust towards the middle, tapering towards both ends.
towards the mouth the tentacles become thinner and thinner, as also their
suckers become smaller. Yet the arms' muscles remain strong in this area,
and united. Thus an octopus can exert strong forces close to its mouth.
the arms become gradually thinner towards their tips, with ever finer suckers,
eminently suitable for sensing objects and for moving objects around and
food towards the mouth.
towards their tips, the arms become more and more sensitive to smells and
tastes, such that an octopus does not only feel the shapes of objects,
but also what they taste like. However, it appears to have its strongest
sense of smell somewhere inside its body bag, as can be seen from its behaviour.
Whenever it touches a strange object, like one's hand, it afterwards enters
the tip of that tentacle into its body cavity where it apparently can taste
whatever molecules were passed to that tentacle.
the suckers on its slippery tentacles have tremendous holding power, which
gives it an enormous advantage as anyone trying to confine it, will experience.
Whereas an attacker has practically no hold on its slippery skin, an octopus
has a firm grip with dozens of suckers of several arms, whenever it chooses.
even though the arms are entirely floppy, an octopus can still reach out
by stiffening their internal cores with internal fluid pressure and muscle
because an octopus has neither an internal nor an external skeleton, it
makes use of the hard objects around it. Rather than pushing itself along
on its arms, it pulls itself forward by its scouting arms. It also uses
hard objects as an external armour.
when an octopus 'walks' around, one can see that its small brains are overwhelmed
by the many signals it receives: from its sharp eyes, from its scouting
tentacles, shapes, smells and so on. In addition it controls the colour
and texture of its skin as it goes. All truly amazing and incomprehensible.
How to lose an arm While we were filming octopus and how they move, we caught
a large octopus by enticing it out from underneath the rock where it lives.
At the time we were also surrounded by inquisitive fish, snapper and blue
cod. As soon as we held the octopus, a blue cod attacked and within two
seconds bit off an arm. It did this by biting it high up where the arm
begins, and then spinning around at a rate of about 4 times per second.
To remove such an arm with a diver's knife would certainly have taken a
lot longer. While scurrying away, the blue cod was persecuted by snapper
and a fight ensued for the severed arm, resulting in everyone getting a
bit. Then another blue cod attacked. We now had an octopus with only six
arms and not much would be left had we not returned it to its safe lair
under the stone.
The ninth hand The jet pipe of an octopus is more than just for swimming
and breathing. It uses it for all kinds of purposes. It is an excellent
digging tool for removing sand and it can puff at animals that come too
close for comfort. Female octopuses use it to spout their eggs towards
their finest suckers by their mouths, and later to aerate the eggs and
to keep them clean from sediment. But it can also be used to feel around,
while not exposing its arms. It works like this:
Imagine yourself in your garden with a garden water hose.
Adjust it to a firm spout while standing in front of an object like a tree.
Now close your eyes while moving the spout around. Every time it hits the
tree, you feel the nozzle in your hands recoil because the water's recoil
at the tree is passed up through the water spout. With your eyes closed,
you are now able to get a fair idea of the objects around. This is how
an octopus uses its water spout to feel around.
It also uses the spout to flush out crabs from their
Killing the lights Our octopus tank is very well secured, but in its ceiling
of overlapping glass panes, tiny gaps of no more than 1cm squared can be
found. One octopus found this by squirting its water spout around and finding
no resistance. With the spout it could now explore what was hanging above
its tanks - a fluorescent light. At one end of this light it found a very
unusual sensation, an electric shock! Now one would think that this electrocution
would have put him off for good, but this was not so. Instead it was fascinated
by it, trying again and again, and getting shocked many times. In the end
the light shorted out and its terminal pins gave way. The octopus had destroyed
the whole armament, and it needed to be replaced. Of course the 1 cm gap
was taped over afterwards. Now get a mental picture of this, as all the
while the octopus hung down from the ceiling panes above the water, its
body dipping sufficiently low into the water for it to be able to breathe
Liquefying the sand The sand octopus is found in good numbers inside a sheltered
harbour where also good numbers of shellfish are found, and where the tide
does not go out. One such place is Whangamumu Harbour, just south of Cape
Brett and the Bay of Islands. It is a favourite shelter for yachts and
runabouts staying the night. Because of its shelter, the sand there is
fine, not a problem for clams, the biggest ones burrowing deepest. For
an octopus to catch a meal, it has to dig down to the level of the clam,
and even deeper as the clam tries to escape. In the meantime the fine sand
keeps caving in, rendering the exercise futile. I've tried to do this myself,
but the crater I create becomes wider and wider rather than deeper.
Then I happened upon a small crater of no more than 20cm
across (the size of a hand). It had caved in by about 2cm (a finger's width),
showing a perfectly horizontal plane of fine sand, rather than a cone.
I touched the sand inside the crater, and it was completely liquid, allowing
me to reach all the way down to the bottom, some 25cm down (to my wrists).
What was going on here? Why had the crater not collapsed?
I then realised that octopuses have a trick up their
sleeves, being able to liquefy fine sand by pumping some of their ink (a
protein mix) into it. Once the sand is liquefied, the octopus just needs
to reach down and pull its victim up. That day I found several liquefied
Coveting shiny objects Octopuses appear to like shiny objects. Underwater photographer
Kim Westerskov recalls an encounter with a large octopus that had no fear
at all. It walked right up to him and grabbed his underwater camera, subjecting
it to a thorough inspection. What's more, it wanted to take off with it.
So a fight followed, and the octopus backed off. However, the camera's
lens had been bent and could not be used again.
I had a similar experience at Great Barrier Island when
a large octopus made a beeline for my movie camera. It pulled at the camera
and could have done damage to it, but recalling Kim Westerskov's experience,
I went along with it. Instead I used my movie lights to distract it, and
the animal let go. But it stayed around, watching my every move as I was
While diving at Island Bay in Wellington, my camera suddenly
was jerked sideways, as an octopus was intent on keeping it. After I managed
to pry the animal from the rock, I also managed to hand my second camera
to my son, who then filmed the affair. It ended all happily, giving both
the octopus and us an unforgettable experience!
octopus sex The male octopus has one special arm (third right) which is slightly
modified for mating. Along its side runs a shallow groove through which
its spermatophores can travel towards its tip. Inside the male's body,
the sperm is packaged into larger packets (spermatophores= sperm
bearers) that can swim, and that have a trigger mechanism to open it. The
male inserts its inadequately short penis into the base of the groove,
and sperm collects at the very end, which is called a hectocotyl
(Gk: hectos= hundred; cotyle= cup). Hence an octopus is the
only animal with an extension penis!
Females have a special receptor inside the bag, for the male's sperm which
can lay dormant for weeks inside the body of the female. When laying her
eggs, the female fertilises them while the male is long gone. Like all
cephalopods, octopuses lay large eggs with lots of yolk, and encapsulated
by a tough membrane. After several weeks the young hatch as complete miniature
adults, without going through a larval stage which is common in other molluscs.
Once freed, they swim with their small jet pipes, changing colour and spouting
ink! The baby octopuses are very good at hiding and are seldom seen.
The sand octopus (O. gibbsi) assembles her eggs into strings,
hanging down from the ceiling of her lair. This is very similar to the
Mediterranean octopus (O. vulgaris). But the reef octopus (Pinnoctopus
cordiformis) pastes her eggs flat against the top and sides of her
den. Because this octopus lives inside rock cavities with narrow openings,
its eggs cannot be seen by divers and underwater photographers.
f021733: when mating, the female hides in her den while the
male remains at arm's length. With his mating arm he visits the body bag
of the female as shown here. (Octopus gibbsi)
f021732: closeup of the female and the male mating arm entering
her body cavity where packets of sperm (spermatophores) are deposited.
When laying her eggs, the female breaks these sperm packets to fertilise
her eggs herself.
f002706: a female sand octopus lays her eggs through
her jet pipe which she funnels really small onto her mouth. Each egg has
a sticky thread. With the finest suckers around her mouth and using her
finest tentacles, she gathers the eggs into strings and attaches these
to the wall.
f022604: a female octopus guarding her strings of eggs inside
her safe den. This sand octopus cements her eggs to the ceiling of her
den and then ventilates these with her jet pipe. She stops eating and will
die shortly after her eggs hatch. Notice the absence of large suckers on
her arms. This is a very large female, compared with the little slender
roughy fish in middle right.
house with a view Octopuses are quite ingenious in the ways they seek out a suitable
spot, and in the ways they adapt such a spot by dragging stones towards
f010715: even though an octopus is well camouflaged, its
presence can often be seen from a distance. Notice how a number of stones
have been dragged together and some turned, showing their white bottom
sides. The octopus sits behind the small dark hole, in this case a large
female sand octopus guarding her nest of eggs.
personality Because octopuses do not live long lives, we return our animals to
the sea before winter, in order to allow them to mate before dying. This
also implies that in spring a new, young one needs to be caught. To our
surprise, each octopus had a different personality which showed in their
behaviour and preference for certain games. It also showed in the manner
they reacted and played with people, and in the way they entertained themselves.
f950626: a young girl has befriended a male octopus. By visiting
it regularly and touching it, she established a relationship that remained
unique. Here she is touching a male octopus who appears to like it. Notice
the few large suckers on this reef octopus (Pinnoctopus cordiformis).
Only males have such large sucker cups.
f217309: the octopus crawls out of its tank to shake hands
with children who quickly discover that an octopus is not a horrible animal
but can be quite affectionate. Several children have wet hairs from the
octopus' playful water spouts, which can be very accurate. Notice the fluorescent
lights above the octopus tank.
Shaking hands with children In the Seafriends' marine aquariums we have a tank dedicated
to a single octopus. It is almost hermetically sealed, for octopuses are
escape artists and can squeeze themselves through very small holes. We
catch a baby octopus by placing a peanut butter jar under water, hidden
in between some rocks. Soon enough a small octopus will make this its home.
Catching it then becomes simply placing one's hand over the jar and quickly
screwing the lid back on. In the aquarium the octopus soon finds its way
out of the opened jar, but then our 'training' begins. Every day we spend
half an hour 'playing' with the octopus, which in the very beginning consists
of merely putting one's arm in the tank, and then day by day closing in
on it. Finally it will reach out to our hand, and eventually the pulling
and pushing becomes play. By about three weeks, an octopus is 'tamed' and
has no fear. It can then also be fed by hand.
When schools visit Seafriends for an unforgettable day
out, the tank is opened to allow children to interact. Soon the octopus
hangs over the glass, extending its arms to say hello, while children scream
from excitement, and from their suppressed fears. Only the very daring
allow their hands to be held by the octopus.
Because octopuses grow so fast, we have to return them
to the sea before winter, and catch a new one in spring. Unfortunately,
after many years, the octopus had to make room for the creation of a complete
ecosystem where the aquarium's sea water is no longer replaced but only
recirculated. In such a system, an octopus becomes an unbearable burden,
as it is rather voracious while growing fast. Perhaps later when our ecosystem
has proved itself, can we have another tame octopus.
other inkfish In New Zealand only few of the many described cephalopods can be found
in shallow water, and these we'll parade here.
Midget octopus, Octopus huttoni Often on scallop beds a miniature octopus is found, small enough to
live inside a scallop shell. Being so small, it is very hard to find, but
scallop fishermen often encounter it amongst their catch.
f012303: the midget octopus is a very small species of octopus,
no larger than one's thumb when mature. Here it has made a tiger shell
its home. (Robsonella australis, Octopus huttoni)
f012313: midget octopuses are often found on scallop beds.
Don't be mistaken. They can be very assertive and aggressive!
Sepiola (Sepioloidea pacifica) The
sepiola is only the size of one's thumb nail, a tubby squid with two little
wings on the sides. It lives in sheltered places such as the entrances
to deep harbours, and hides in fine sand. At night it rises not far above
the sand, where it swims around, catching prey. When confronted with the
diver's light, it dives back to the bottom where it disappears completely,
partly by camouflage and partly by burrowing. Photos of the New Zealand
sepiola are understandably rare.
The NZ sepiola is nocturnal and rather rare, so we do not
have a photo of it. But here are two tropical sepiolas photographed while
mating. Truly amazing!
Photo courtesy Cal Mero, Australia.
f038535: a diver finds two spent paper nautilus shells.
These are very fragile and disintegrate within a few months.
Paper nautilus (Argonauta nodosa) The paper nautilus lives in deep water but in spring (October-November)
females seek shallow water to deposit their egg cases. It is a hazardous
task because the animals have no defence against predatory fish and diving
sea birds (petrels and shags), so they do this at night. The egg capsules
wash up on beaches of remote islands like Great Barrier Island, and they
fall in between rocks where divers find them. The paper nautilus shell
is extremely fragile and dissolves back into seawater within a few months.
It is not known whether females return to the deep and whether they
return year after year until they die. Most likely they will make the trip
only once and die soon after. However, their egg capsules are found in
various sizes, from as little as 5cm across to as large as 25cm, suggesting
that some do not grow well during their short lives.
The female has two flattened arms that secrete the shell, as they also
hold it. The male paper nautilus is very small indeed but with an extended
mating arm which can be detached and left inside the female's mantle cavity.
Paper nautilus (Argonauta argo). The paper nautilus
shown here is not precisely the one found in New Zealand
nodosa) but looks very much like it. Notice the flattened arms for
moulding the egg capsule. The egg mass shown here outside the capsule,
is normally located inside. On the right the tiny male with his long hectocotylus.
Ramshorn squid (Spirula spirula) The
tiny ramshorn squid lives in deep water, never far from the bottom. It
has an internal coiled and chambered shell for buoyancy (about 3-4cm across),
and tiny fins at one end, allowing it to go up and down in the water column
without the hassle of the air expanding. When they die after breeding,
and become decomposed by other creatures, their intact shells float up
to the surface where winds may blow them ashore in large numbers. The spiral
shells easily break apart.
Broad squid (Sepioteuthis australis) The broad squid hunts over the continental shelves, never far from
the bottom. It hunts in small packs of a few to 20-40 individuals. In spring
it comes to the shallows where females lay their eggs and attach these
to stick-like objects like the stalked kelp or finger sponges. Each egg
capsule comes with a sticky thread that is carefully wound around the stick.
After a few weeks to one month, the young hatch as miniature individuals,
changing colour, swimming with their jet pipes and squirting ink - instant
f041707: This ink fish is a young broad squid (Sepioteuthis
australis). Squid and cuttlefish have ten arms, two of which much longer
than the others. Hidden inside skin folds, they can shoot these tentacles
out to catch unsuspecting prey, and they are very good at it.
f049334: a young broad squid (Sepioteuthis australis).
Notice its wings spanning its entire body. With these wings they can move
forward as easily as backward, and they can maneuver in all directions.
But when fleeing, they use their jet propulsion. Within 6 months they mature,
and they die before the end of the year, weighing over 1kg.
f049328: a marauding band of young broad squid. By changing
colour, they can camouflage themselves while sneaking up to an unsuspecting
triplefin or other small fish. Once the long catch tentacles shoot out,
there is no escaping.
f025811: a cluster of broad squid eggs attached to a stalked
kelp. Each egg capsule has 4-6 embryos and a long string which the female
attaches securely to a stick-like object. Capsules feel rubbery and stretch
likewise. This cluster is the work of perhaps 5 females working together
or in succession.
f039815: details of squid egg capsules. First the capsules
are opaque white, but by the time the little squids hatch, they become
transparent, clearly showing the baby squids inside, with their large eyes.
The brown 'paint' is probably a benthic dinoflagellate (Ostreopsis).
f039812: under water one can 'pop' a squid egg, which releases
the little squid inside. Here is a 10mm small baby broad squid, still with
its egg sac. Amazingly, they can change colour rapidly and also spout ink!
Notice the chromatophores (colour cells) and very small fins that will
Night dive with squid While swimming back from a night dive in Leigh harbour,
I happened on a school of large broad squid that were attracted by the
permanent lights on the wharf. Having seen how fast a broad squid can demolish
its prey with its parrot beak, I was rather intrepidated, being surrounded
by fifty of these devouring beasts. But they were just interested in the
movie lights. The most courageous one shot forward, grasping the light
and holding on to it. That gave me a chance to stroke its almost luminescent
green-white belly, something it appeared to enjoy as it was flashing wave
patterns over its back, which immediately drew the other squid nearby.
Then they had turns clasping the light while being stroked, and their skin
patterns became weirder and flashier! They were crowding around me, keen
not to miss a moment. Then the battery ran out.
squid (Nototodarus sp.) New Zealand has two species of arrow squid, the smaller Nototodarus
gouldi (26cm) around the North Island, and the larger Nototodarus
sloanii, (30cm, 1kg) around the South Island where it thrives profusely
in the upwellings of the Subantarctic Front. The map shows their respective
distributions. The Subantarctic Front is an upwelling area between the
cold subantarctic water and the warmer temperate water that engulfs New
Zealand. Sea life is very rich there, with large predating sea mammals
like fur seals, dolphins and sperm whales surrounded by untold many sea
birds, including yellow-eyed penguins.
These arrow squids are fast swimmers, growing from a 4mm egg to maturity
in a mere 200 days, when they mate and die. Females blow a mysterious egg
capsule, a kind of balloon, measuring over one metre across. It is not
known how they do this, but it may begin with a much smaller egg capsule
which grows by itself by drawing water from the outside through the process
of osmosis (water going through a membrane from a lower to a higher concentration).
See photograph below.
In 1982/83 and 1983/84 the NZ squid catches were 63,700 and 87,000
tonnes of which 71-94% was N. sloanii.
An arrow squid (Loligo opalescens) from California
is laying a complicated egg capsule in an egg-laying frenzy. Afterwards,
one finds these egg capsules tied together in large masses, lying on the
sandy bottom, while the parents die.
Photo courtesy Scott
f052307: the NZ arrow squid (Nototodarus sloanii)
lays capsules as shown left, but does not attach these. Instead they float
around, gradually growing (by osmosis?) to transparent balloons of over
one metre across. Inside these tough membranes, their offspring is well
octopus encounters Meeting an octopus underwater always brings a sense of excitement because
each has its own personality. One can learn from octopuses in books and
even on film, but it can never replace an encounter with a live octopus
under water. Here are some examples.
f035330: a young reef octopus (Pinnoctopus cordiformis)
hunting in the night. Octopi can feel and taste with their many arms, and
do not need their excellent eyes for hunting prey. The reef octopus feeds
mainly on crabs and crayfish. It is not an engineer and lives in a narrow
hole in the rocky reef. (Pinnoctopus cordiformis, previously Maori Octopus,
f028305: a sand octopus (Octopus gibbsi) has crawled
out of its protective den which it carefully built underneath large rocks.
The sand octopus is an engineer who changes his environment to suit. Around
its den one finds the remains of its meal, in this case various burrowing
House with a view Because octopuses have such excellent eyesight, they
like to live inside a house with a view, rather than in an alley. Particularly
the sand octopus has this preference. Being also a predator, eventually
exhausting its food supply, it also needs to move frequently. It is not
uncommon for an octopus to have various work huts in addition to the mansion
with a view, where it returns. One can often find an octopus just sitting
on a perch, enjoying the goings-on around it.
f033529: octopuses like to see what is going on around them,
like this large sand octopus resting well camouflaged outside its den.
Around its entrance one finds shells from previous meals. The author often
finds rare shells here.
f039936: this sand octopus is tending and guarding a large
trumpet whelk (Charonia rubicunda) for its next meal. (Octopus
f022819: a large sand octopus has but little time for the
diver because inside its web it has caught a smaller octopus, which is
to be cannibalised. In a fleeting moment it shakes hands with the diver.
f022826: the octopus swims to its den inside a disused and
decaying lobster pot to eat the large meal (another octopus) held inside
its web. Notice the other empty shells around. (Octopus gibbsi)
f009125: octopus are not only predators but also scavengers
with a keen sense of smell. That is why they are so easily caught in crayfish
pots and lobster traps. Here a sand octopus is feasting on a dead conger
eel, thrown overboard in a fishing harbour.
Digging through gravel Leigh Harbour attracts octopuses for an easy meal from
bait and fish innards thrown overboard. One day I saw a fine small octopus,
just the right size for our aquariums. It sat in the open on a large mound
of gravel, heaped up by the propellers of fishing boats. It would be an
easy catch as it had nowhere to go, and I could easily outswim a little
one like this. So I quickly grabbed it and that would have been the end
of it. However, constraining a live octopus, even a small one, is a tall
order because it has a slippery skin and is very strong for such a little
fellow. To my embarrassment, it escaped and began digging into the heap
No problem here because a grown man can dig much faster.
But then my disadvantage began to show. As the octopus was digging deeper,
it placed the spoils behind it, whereas I had to displace the spoils in
order to keep the hole from caving in. It didn't take long for the little
fellow not only to disappear from sight, but also nowhere to be found!
It had literally vanished into the heap of gravel.
f017723: most of the time an octopus moves around slowly
on all of its eight legs, crawling while testing every bit of its surroundings
with the tips of its many legs. (Pinnoctopus cordiformis)
f040311: an octopus can swim quite fast by blowing water
out of its jet pipe. It sucks water in by opening its body bag and it squirts
water out by sealing this bag against the jet pipe. The jet pipe is an
octopus' ninth hand.
f022809: a skin diver finds a baby octopus well hidden underneath
a protective rock. Octopus are very hard to find because they camouflage
themselves so well. However, because they turn stones nearby, they can
at times be spotted from a distance.
f003708: being soft all over, an octopus loves hard things.
Here it is using hard shells as an impregnable armour. A little fellow
like this should have been scared by the much bigger diver, but its inquisitiveness
Cousteau 1975: Octopus
Hanlon, Robert T & John B Messenger
(1998): Cephalopod behaviour. Cambridge University Press.
Lane, Frank W 1957: Kingdom
of the Octopus.
O'Shea, Steve 1999: Octopoda
(Mollusca: Cephalopoda). Biodiv mem 112, NIWA
Powell, AWB 1979: New Zealand
mollusca: marine, land and freshwater shells. Collins.