Download Squid Dissection

Squid Dissection Lab
Purpose
This dissection of a small squid is presented in the format of a written document including
photographs which serve to demonstrate the required dissection and identification of major
components.
Part A – Observing the External
Anatomy of the Squid
Picture 1 – Squid presented
Dorsal side up (dark side)
Picture 2 – Squid presented
Ventral side up (lighter side)
Picture 3 – Chromatophores
(freckles)
Picture 4 – Fins
Picture 5 – Mantle
Picture 6 – Siphon (the
propulsion unit)
Picture 7 – Eyes
Picture 8 – Tentacles (two of
these)
Picture 9 – Arms(eight of
these)
Picture 10 – Suction Cups
Picture 11 – Mouth. The beak
is inside the mouth and hard
to see but can be felt as a hard
structure
Picture 12 – Gills
(attached)
Picture 13 – Gills
(detached in
bowl of water)
Picture 15 – Ink Sac
(removed) Picture 14 – Ink
Sac (on top of the liver)
Picture 16 – Heart (2
branchial for the gills)
Picture 17 – Heart (1
systemic for the rest of
the body)
Picture 18 Buccal Bulb
Picture 19 Gonads (this
specimen is …..male or female)
Picture 20 – Pen
Picture 21 – Pen and
Ink utilized
Picture 22 –Eye
Picture 23 Cornea
Picture 24 Lens
Discussion Questions
Identify the following;
1. Kingdon; Squid belong to the kingdom Animalia, multi cellular, eukaryotic organism.
Animalia includes organisms such as Sponges, Worms, Insects, Fish, Birds and Mammals.
2. Phylum; Mollusca, one of the most diverse groups of animals with at least 50,000
species
3. Class; Cephalopoda, among the most intelligent, most mobile and among the largest of
all molluscs
Living things are classified in a hierarchical taxonomy. There are Seven basic levels to this
Hierachy
a) Kingdom - there are 5 categories (Monera, Protista, Fungi, Plantae, Animalia)
b) Phylum – there are 16 categories of Phyla (Annelida, Arthropoda, Brachiopoda, Bryozoa,
Chordata, Coelenterata, Ctenophora, Echinodermata,Mollusca, Nematoda,
Nemertea, Onychophora, Platyhelminthes, Phoronida, Porifera, Rotifera)
c) Class – now we are getting into larger numbers and some debate between scientists but
broadly speaking there are around thirty five different Classes (Amphibians, Arachnids,
Barnacles and more, but including our own Mollusca)
d) Order – a way to categorise related organisms; a smaller group than a Class but bigger
than a Family or Genus.
e) Family – a way to group closely related organisms; each family may have many
members or just a few
f) Genus – a way to show that species are closely related to each other; for our Squid the
Genus is Architeuthis
g) Species – a group of organisms that can interbreed and produce healthy offspring
Define the meaning of the Phylum Name;
Phylum is a taxonomic rank. It is below Kingdom but above Class. So with respect to our Squid it
is within the Kingdom Animalia and then within the Kingdom Animalia the Squid is part of a sub
group (Phylum) called Molusca.
Within the sub classification Phylum animals are grouped together based on similarities in body
plans or organization. So, in this case we are interested in the classification of Mollusca; there
are some 33 different classification of Phylum (humans are members of the Phylum Chordata).
Meaning of the Class Name;
So we have our Squid being a member of the Kingdom Animalia, and then within the Animalia
Kingdom, the Squid is a member of the Phylum Mollusca. Now, within this classification
(Mollusca) we have the Class Cephalopods which is the class for our Squid.
Additional information is that our Squid (a Cephalopod) is a member of the Order (next level
down from Class) Teuthida.
Gender of the Squid dissected in this lab; Male
Identification of 3 evolutionary adaptations that the Squid possesses giving it a
selective advantage as a predator – expand on the selective advantages.
Squids have some very distinctive and even unique adaptations for their chosen environment.
There are around 375 different species of Squid and all have 10 arms (2 of which are called
tentacles and are slightly longer than the other eight).
1. Very large eyes in relation to its body size and when compared to other organisms
within its environment. These eyes are very well developed exhibiting extremely good
eye sight enabling them to see upwards of 120M meaning that they are able (just) to
see one of their primary predators (Whales) before it is too late.
2. A distinctive method of catching its prey (it is a carnivore) – the squid uses its two arms
(tentacles) to actually catch its prey and then retains or manipulates the catch using its
eight arms.
3. Having successfully caught its prey (hard or soft shelled/skinned) the Squid will use its
very hard beak to break into its prey.
4. Squid can change colour in order to blend in or hide from their predators (or maybe
even just to momentarily confuse predators).
5. They can eject a large plume of dark ink which renders a predator blind or at least
confuses a predator for long enough to enable the Squid to make good its escape. The
Ink Sac empties directly into the water jet.
6. And on the subject of escape; a built in jet pack with a 360 degree directional nozzle
that allows the squid to travel at speeds up to 30mph.
7. Maybe not unique but tried and tested; Squid travel in groups meaning that those on
the periphery or the weakest are most vulnerable to predators (survival of the fittest)