Squid Anatomy


Watch the video below and read the background information.

(Channel, 2010)

Background information:

Squid are a part of the Phylum Mollusca, which means “soft-bodied” in Latin and includes animals such as clams, oysters, snails, etc. It has two main sections – the mantle (which is a modified ‘foot’) and the head (with the arms attached). It is therefore part of the Class Cephalopoda, which literally means “head-foot”. Octopus, cuttlefish and the ancient nautilus are also Cephalopods. Cephalopods  are unique invertebrates because most do not possess a hard outer shell (except the nautilus). All cephalopods are marine carnivores.

Squid are one of the most highly developed invertebrates, and are very intelligent. They also have some extremely diverse and interesting anatomical features.

Squid can be as small as a thumbnail, or as large as a house. The giant squid, Architeuthis, can measure 60 feet in length and weigh three tons! Squid are an important part of the ocean food web; they are a major food source for many fish, birds and marine mammals. Squid are gaining popularity as a food source for humans around the world (calamari). However, over-fishing is a growing concern because there are no regulations on squid harvesting. About 6,000 metric tons of wild squid are taken yearly for human food and bait.

Some of the animal’s structures explored in this lesson illustrate the ways in which the squid has adapted to life in the ocean. Its streamlined body and jet propulsion make the squid a fast, active predator. This animal also has a very good defence mechanism. Cephalopods are masters of colour change and camouflage. They have specialised pigment structures called chromatophores in their skin, which allows them to change their skin colour swiftly and at will.

'Digital Disection'

This lesson will focus on the external and internal anatomy of a squid.

You are to 'digitally disect' a squid in order to learn about their anatomy and physiology.

At the end of the digital dissection label the picture of a squid on the printed pages to demonstrate your knowledge.

By the end of this lesson,

You will be able to:

-       Appropriately label a basic scientific diagram.

You will know:

-       Basic structure and function of a cephalopod’s anatomy.

Virtual Dissection

Click on the link below or copy and paste the URL into a web browser:

http://squid.tepapa.govt.nz/anatomy/interactive  (Museum of New Zealand, 2004)

Follow the instructions below and take note when you find each of the body parts.

External Anatomy:

Find each of the parts.


1. Locate the water jet. The water jet is found on the ventral side of the squid.

2. The tentacles (long) and arms (short) are attached to the head of the squid. 

3. Find the two large eyes on the side of the head. 

4. Locate the body, which is covered by the mantle, and locate the two fins. 

5. Each arm has sucker disks, count the number of sucker discs on one arm.













Internal Anatomy

1. Find the ink sac, this is a small dark sac near the water jet. 

2. Find the esophagus, this is best found by looking into the mouth and seeing where it leads. The muscular mass that surrounded the beak can be pulled up (and out) to show the tube that is the esophagus. 

3. To find the stomach, follow the esophagus toward the posterior. 

4. The anus empties into the water jet. Find the anus. 

5. Locate the gills, these are feathery structures that may be hidden under other things, there are two of them. 

6. Follow the gills toward the interior to find an enlarged structure at their base: this is the gill heart. 

7. All the way toward the fin is a whitish or yellowish structure: this is the gonad. The male gonad is generally white, the female gonad is usually more yellow to clear. Is your squid male or female? 

8. The hard shell-like structure that lies along the backside of the squid is the pen. The pen serves to stabilize the squid while it swims (like our backbone).

Complete the sheets!

Complete the printed sheets given to you by your teacher by labeling the diagrams and answering the questions.

If you are unsure of any answers, use the squid anatomy website as mentioned on the last page.

Well Done!

Squid have an important place in the marine ecosystem. Unfortunately, due to their open mantle, they are particularly sucesptible to pollution as their internal organs are not protected.

In the next part of our unit we will be looking at how anthropogenic (caused by humans) pollution is impacting on squids.

Channel, P. (2010). YouTube. Swimming Squid at Sharks Cove on North Shore Oahu, HI July 4, 2010. Retrieved 2015, from https://www.youtube.com/watch?x-yt-ts=1421914688&x-yt-cl=84503534&v=Nf2iRRWH5OI

Museum of New Zealand. (2004a). Museum of New Zealand Te Papa Tongarewa. The Colossal Squid. Retrieved January 20, 2015, from http://squid.tepapa.govt.nz

Teachers please print these pages to assess student learning.

Squid Anatomy Worksheet


1. How many arms does the squid have? _____   How many tentacles? ______

2. What is the function of the arms and tentacles? ______________________

3. What is the function of the water jet? ____________________________

4. Name two features that are adaptations for the squid's predatory life. ____________________________________________________

5. Name two traits that the squid shares with other mollusks. ______________________________________________

Word bank:




Water Jet






Use the descriptions above to help you label the squid


Observations and Analysis

1. How many gills does the squid have? _______________________________

2. Where does the ink sac empty into? ___________________________________
What is its function? ___________________________________________________

3. What is the function of the pen? ________________________________________

4. Where do wastes exit the squid? (be specific) ___________________________

Word Bank



Ink sac






Use the descriptions above to help you label the squid