The purpose of this dissection was to acquaint ourselves with the anatomy of a squid and to compare it with other mollusks. We noticed how the tentacles and arms were really just a modified version of a standard foot and how the squid had an internal shell in comparison to clams and oysters who have external shells. Squids also possess radulas which are common to all mollusks except for bivalves. One glaring difference between squids and other mollusks was their well-developed compound eyes. I dissected one of the eyes and learned that the lens of the squid was actually quite large compared to its body (picture below).
While squids are colour blind, they have highly developed sight and can somehow control their cromatophores to blend in with their environment. Unlike many sessile mollusks, squids are motile and agile. They use their funnels and jet propulsion to move themselves. This adaptation allows them to hunt effectively.
During the dissection, we were also able to find the ink sac. Many cephalopods squirt out a cloud of ink when they are threatened. This allows them to make a quick getaway. They squirt out ink from the funnel.
It was very interesting to try to write with squid ink. Unlike normal ink in our pens, it is not as fluid but quite dotty.
The squid we got had 8 arms and 2 tentacles. All of them have suckers to aid the squid catch prey.
The shorter arms grab and hold prey. They also bring it to the squid's mouth. The longer tentacles are for capturing prey that are further away.
The squid moves by releasing water from its funnel (blue arrow) which propels itself in the opposite direction of where the funnel is facing.
The squid uses its arms and tentacles which are lined with suckers to capture and immobilize its prey.
Another adaptation that helps the squid's predatory life are pigment cells called chromatophores. Chromatophores expand or contract to display or hide different colours which helps the squid surprise its prey or hide from predators.
Squids, like many other mollusks, are bilaterally symmetrical and are coelomate.
Another trait that squids have in common with other mollusks is the basic body structure. They all have a foot, a mantle that covers the body, and the visceral mass containing most of the organs.
Squids have one pair of feathery gills for respiration (outlined in yellow).
The ink sac empties into the funnel. When the squid is agitated or feels threatened, the squid will shoot ink out of its sac and funnel, into the water to create a smokescreen of sorts to escape.
The pen is the squid's internal shell. It supports the mantle, keeping the squid upright, allowing it to float in water. If the squid did not have a pen, squid's body would have no support and would just flop around.
Solid waste exits the squid through the anus out of the siphon. Waste produced from cellular metabolism is removed from the blood by tube-like organs called nephridia.
While it was difficult to distinguish the inner organs from one another at the beginning, everything became clear after we identified the ink sac. I had a very interesting time comparing the different structures of the squid to other mollusks. Its quite amazing to see how a basic body part could adapt into so many different forms depending on the purpose. The only thing that disappointed me in this dissection was the fact that we could not eat the squid afterwards. We threw out all the squid which could have been a delicious lunch.
On an end note, I think the squid would win: dinosaurs are extinct because they were unable to adapt to changes in the environment while squids are still around today. And the whale is too apathetic to get involved. Or maybe I'm just rooting for the squid because it is the cutest.