Transcript Squid dissection - IGCSE Biology Wikispace

Procedure for Squid Dissection
1. Label external anatomy.
Place the squid with the dorsal
(back) side up in the dissecting
pan (fin side up).
Use the hand lens to examine the
suckers on the tentacles and
arms. Pop out one of the
supporting rings in a sucker using
your fingers.
Spots or chromatophores on the
skin are cells containing pigment
surrounded by a muscle that can
make them swell in size.
The squid can change colour
rapidly to camouflage
themselves, attract mates, and to
communicate with each other.
1. (b) Label the funnel
Turn the body over, ventral
side up, and locate the
funnel (a deflated fleshy
tube located at the base of
the head).
A squid swims by squirting
water from the mantle
through the funnel. The
direction it swims depends
on which way the funnel is
aimed.
Move the funnel and note
its flexibility.
2. Remove beak and
radula
Open and close the beak.
Pull out the beak.
Manipulate them (open
and close) as if the squid
were eating.
When you remove the
beak you may see a long
tube attached to it. This is
the oesophagus, the food
passes down the
oesophagus to the
stomach at the other end.
Radula for scraping
tearing and
gripping prey.
3. Open the mantle
Keep the squid on its back
(the side opposite the funnel
and dorsal fin).
Using forceps, lift up the
opening to the mantle behind
the funnel (near the head)
and separate the mantle from
the internal organs.
Cut along the ventral midline
of the mantle, from its
opening all the way to the tail.
Be careful to keep the scissors
lifted away from the internal
organs so they are not
damaged.
4. Reproductive Organs
Female glands lay on top of
the other internal organs.
These glands create the
gelatinous matrix that
envelops the eggs.
The male genital duct is a
white, fluid-filled sac in the
posterior end (back end) of
the mantle. The sperm are
stored in thin tubes in an
elongated sac behind and
along one gill.
5. Locate the gills.
These are the long, feathershaped organs that are
attached to the sides of the
mantle and extend along the
anterior (front) half of the
mantle.
Identify the gill hearts, one
on the posterior end of each
gill (these are small, flat and
white).
Questions: Why are they
white and our hearts are red
or purple?
The squid has a third heart
(the systemic heart) that
pumps blood to the rest of
the body.
6. Digestive Tract (light
brown)
The long, silvery dark tube on top of
the liver is the ink sac. Leave it for
now.
Locate the stomach and caecum.
These lie together as one white,
silky-looking tube, like a deflated
bladder and a coiled sack.
If you are curious about the liver,
wait to cut it open until the end of
the dissection. It contains a lot of
brown, oily liquid which may obscure
other organs.
If possible, open the stomach and
examine its contents. Many squid
will have bits of partially digested
crustaceans (pink and white pieces),
or tiny fish scales and bones.
7. Observe the Ink Sac
The silvery-black ink sac lies
connected to the intestine.
Be careful not to puncture it yet.
Squid ink stains clothing and
skin.
8. Remove the Gladius (Pen)
The gladius is a long, clear
feather-shaped structure used
to support the mantle and for
organ attachment. It and the
cranium, or brain case, make
up the "skeleton" of the squid.
It feels like plastic and is made
of tissue similar to a shrimp
shell.
Pry out the tail end of the
gladius and pull straight back,
away from the body.
8. (b) Write with ink and gladius
Gently pierce the ink sac with the
pen.
Then, using only the ink-filled tip of
the gladius, write your name on
your squid illustration or paper.
If the ink seems dry and pasty, add
one drop of water at a time to
create fluid ink.
Squid ink was actually used to write
and draw in ancient times.
9. Remove the eye lens
If you carefully snip open
the eye you can remove
the hard lens with your
fingers. It is round- human
lenses are oval.
Squid can tell the
difference between light
and dark, blue and yellow
and forms a complete
image of whatever it is
looking at.
10. Remove the brain
Go through the mouth
with your tweezers and
grasp the brain and the
long nerve attached to it.
Carefully remove and
examine it.
Tentacle hooks and barbs of the Giant
and Colossal Squid
Barbs on a tentacle
Hooks that can swivel 360°
This sperm whale was gouged by
one or more colossal squid during
its life time. This is judging by the
deep scars on its head and the squid
beaks found in its stomach.
Computer
animation
Squid Suckers
(have rings with teeth)
• Suckers on a squid.
Octopus Suckers (no hooks or
hard rings)
The Colossal Squid
New Zealand fishermen
have caught what is
expected to be a worldrecord-breaking
colossal squid.
Fisheries Minister Jim
Anderton said the squid,
weighing an estimated
450kg,took two hours to
land in Antarctic waters.
Local news said the squid
(Mesonychoteuthis
hamiltoni) was about 10m
long, and was the first
adult colossal squid
landed intact.
One expert said calamari
rings made from it would
be like tractor tyres.
Colossal Squid Mouth and Beak
Size comparisons of squid