Octopus (Pinnoctopus
cordiformis)
Octopus
maorum belongs to the Order Octopoda and is one of around 35 species
of octopus found around the coast of New Zealand. The octopus
are actually highly developed molluscs and as such are related
to the less complex shellfish such as mussels and paua.
| They
are however more closely related to the squid, cuttlefish
and nautilus, (as a group they are known as the cephalopods)
which are also found around our coastline. |
 |
Size:
Octopus maorum will generally have an arm span of no more than
1.5 m (even though other species overseas have been recorded
with arm spans of up to 9.6 m!).
Movement:
The octopus is generally a bottom dweller and is more commonly
found crawling around it’s preferred rocky habitat. It
uses its eight arms to pull itself around and the powerful suction
discs found on the underside of its arms help it adhere to any
object (or animal) with ease. When disturbed the octopus can
swim backwards with a blast from its muscular jet propulsion
system.
Nutrition:
Octopus usually live in dens and will either venture out in
search of prey or will wait by the entrance and ambush any unwary
fish, crustacean or other edible invertebrate that passes within
reach. They will leap on their potential prey, enveloping it
within their arms and paralysing it with their salivary toxin.
This may be accompanied by biting and tearing from their parrot-like
beak (the only rigid part of an octopus’ body) in order
to break the animal into digestible pieces.
Reproduction:
The male is easily identified by the third arm on its right
hand side, which has a round spoon-like tip. This arm is used
insert a package of sperm called a spermatophore into the females
body cavity where it fertilises the females eggs. The female
will then lay her eggs in ‘grape-like’ clusters
within rocky recesses, staying to ventilate her eggs by pumping
water over them. She will remain with the eggs until she has
finished brooding them and will then generally die shortly afterwards.
Age:
It is thought that Octopus maorum is fast growing and relatively
short lived, living to about 18 – 24 months.
Did
you know?
The
octopus has three hearts! One to pump blood around its body
and another two help push blood through its two gills.
The octopus has highly developed eyes very similar to those
of fish and can discriminate between objects that are only 0.5
cm in diameter from up to a metre away!
The
octopus can rapidly change its colour to match its background
ie as camouflage, or to display aggression/alarm. They do this
with pigment filled cells called chromatophores. These cells,
which may come in several different colours, can be manipulated
into various shapes through muscle expansion/contraction to
provide a range of different colour concentrations. With help
from reflective cells an amazing array of colours can be shown
within a matter of seconds.
The
octopus can release ink as a defensive mechanism, which it may
squirt in the direction of any potential danger. Rather than
hiding the octopus, this is thought to either confuse any predator
with another ‘octopus shaped’ cloud of ink, or to
discourage the predator with a chemical irritant found within
the ink.
The
large quantity of human refuse found throughout the oceans has
in places been linked with an increase in the numbers of octopus,
as bottles, gumboots etc. can provide them with perfect ‘pre-fabricated’
dens!
The
octopus is an accomplished escape artist, with its body able
to fit through any hole that it can fit its hard beak through!
