Squid Dissection

A very interesting way to finish our school week, our biology classes squid dissection was very exciting, and definitely a lot cleaner than the messy insides of the earthworm we cut into last week. It was also much more hard hitting, as this was something that a lot of people eat (unlike earthworms), and actually finding out what was inside what we eat was a unique experience on its own. Once again we got ourselves ready, arming ourselves with the scalpels, pins, forceps, etc. and dove right into the dissection. Sadly, before we could get into the squid, we had to examine its external anatomy, counting its arms and tentacles, which confused our entire class as tried to find out which ones were the tentacles and which ones were the arms. After the examination, we were ready to find out what the squid, quite literally, was made of. Opening it's collar straight down the middle we found a cornucopia of organs and body parts. The most surprising was the jelly- like mantle, which felt like incredibly fragile jello that could easily break. We were also able to find the ink sac, a silvery, long body part that housed the squid's most flamboyant defense system. Although we didn't open it up, we saw many other groups which were able to get the ink, and even use it to write their names! Definitely the best part was opening the head and finding the beak of the squid. This body part of the cephalopod was incredible, I myself was truly surprised to find a mouth part that closely resembled a bird, even though the two classes of animal were very different. Now with a much better knowledge of the inside of a squid, we were able to fill out our pre-labs which had detailed diagrams that we had to fill out. This dissection was a great experience that showed us how intricate and special all animals are, even the ones that we take for granted, like sea food in this case, and giving us a hands on look at the actual organisms that we were learning about in class. This lab was definitely one of my favorites in the year.

EXTERNAL ANATOMY                                                                                                                              


1. The squid that we were dissecting had eight arms and two long tentacles.












2. The differences between the squid's arms and tentacles are their length and their function. The squid's tentacles are long and only have suckers at the end, whereas the squid's arms are much shorter in comparison yet have suckers all along the inside on them. This would mean that the arms are meant to grasp and keep a hold of prey as well as contribute to locomotion and traction when climbing, and that the much longer tentacles are meant to feel and touch things in the surrounding environment.

3. The flow of water throughout the squid is controlled by the funnel and water jet. The water come in through the funnel, and is then expelled like a jet, in the direction of the tentacles. This causes the squid to propel itself in the opposite direction.





4. Suckers- found on both their tentacles and arms, these numerous, tiny suction cups are made to stick onto surfaces, as well as other creatures. They grasp the prey and the suckers make it impossible to escape.
    Beak- the squids have very powerful beak, that resembles a bird, and is made to tear apart it's prey.   Some species can even secrete a poison from here, paralyzing them.

Tentacles: RED Arms: BLUE

5. The squids have a developed foot, called the tentacles. This is what it has specialized into, like snails and their flat feet they are suited to their environment. The squids also a share a soft body that all mollusks are known by. Although most cephalopods have evolved to not need hard shells for protection, they still resemble all other mollusks in this way. Another similarity between cephalopods and other mollusks are the bilateral symmetry that they exhibit.




INTERNAL ANATOMY                                                                                                                            

1. The Squid has a single pair of gills, each located on one side of the body. This feathery structure is the main source of gas exchange in the squid, exchanging oxygen in the water that it needs to survive.













2. The Squid's ink sac is it's most unique defense and escape mechanism. It empties ink into the squids funnel when it's threatened by a predator. This sudden jet of ink in the water acts as a smoke screen and disorientates the attacker and allows the squid enough time to escape. Some species even shoot out a poison with the ink, paralyzing the intruder for a time.

3. The pin provides structural support for the squid. It is located along the inside of the mantle, and is attached to the muscles. It supports the mantle and is technically a vestigial structure as it used to be a shell until evolution saw fit to remove it. If it was gone, the squid might suffer from a less structured body, but since it is a vestigial organ, it probably won't suffer much from its removal.

4. The squid's excretory system consists of the anus, which is the main way through which waste is released. Another way the squid is able to rid itself of waste is through the water jet, where it can release water, as well as any waste that it may have.







Probably the most interesting part of the lab was finding and opening out the beak to make it more visible. It was fascinating to see how it resembled the beaks of birds even though the two classes of species are very different from one another.