Safety: This activity uses sharp tools. Younger scientists must get an adult to assist with cutting.
You will need
Squid (available from most good fishmongers)
Baking tray
Sharp scissors
Bowl or sink filled with water
Plastic bag
Rubber gloves (optional)
Lemon (optional)
What to do
Give your squid a gentle rinse in the sink to clean it.
Lay it out on the baking tray. Have a good look at its external anatomy (outside body). How many tentacles does it have? Where is its mouth? Where are its eyes?
Find its two longest tentacles. If they look exactly the same, you have a female. If one looks rougher at the end than the other (like short bristles), it’s a male squid.
The mouth is a sharp beak in the centre of the tentacles. Take care not to scratch yourself on it. Use your scissors to carefully cut through the mantle (the tube-like body). It’s this tube which we make calamari from.
Open the body and have a look at the organs. One should be darker than the rest – it contains a dark liquid called ink.
Look at this diagram below to identify the other organs. Can you find the gills? What function do you think they might have?
Place your squid into a plastic bag for disposal when you’ve done. If you didn’t use gloves, you can use a lemon to remove the fishy-smell from your hands when you wash.
What’s happening?
Squid are a type of mollusc, belonging to the same phylum as clams, octopus and snails. They possess a number of features to help them survive in their aquatic environment. They are streamlined to reduce drag when they swim, have large eyes to see in dim conditions, and have a rather complicated (if still relatively small) brain. While squid lack a skeleton, they do have a simple internal structure called a gladius made from a similar material to bug-shells, which supports its mantle and gives something for its muscles to hold onto.
The parts of a squid.
Their tentacles are covered with small suckers which help them grab onto slippery fish for food. Two of these tentacles are longer than the rest – some species use these as grappling hooks to shoot out and snatch prey, reeling them in to be torn up by the squid’s sharp beak.
Males often have special bristles on one of these longer tentacles, used for transferring sex cells into the females.
The ink sac is used mostly when the squid is agitated or upset, releasing a cloud of dark liquid in an effort to confuse or startle a potential predator. Believe it or not, a number of cooking recipes actually use squid ink for colour and flavour!
Applications
In times past there have been stories of massive squid living in the oceans. The evidence for these monsters was easy to find – the whales which preyed on them bore the scars of their suckers on their skin and carried their undigested beaks in their guts. However it has only been in recent years have we managed to find entire, intact specimens to study.
There are a number of squid species living in the depths of our oceans which are capable of growing to immense sizes of up to 14 metres or more. The colossal squid, for example, has the largest eyes of any living thing, each with a diameter of about 30 centimetres. Dissections of deceased squid can tell us a lot about how they live, what they eat and how they reproduce. One female dissected in New Zealand was found to have ovaries packed with thousands of eggs.
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