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.

Our Worm Lab

1. The pumping organs of the Worm are its hearts, or enlarged blood vessels

2. It first enters through the mouth, then the pharynx. It travels through the esophagus and into the crop and gizzard, and then through the intestine until the waste is excreted through the anus

3. The worms brain is made up of several ganglia, which is attaches to a long nerve that runs along the ventral side of its body, which connects it to the rest of the body. 

4. The parts of the worms body that are involved with the excretion of waste are the anus, and the nephridia, (which we could not find our lab sadly)

5. You can find out the worm's diet by looking at what can be found in it's digestive system. Soil for example will be found travelling through the digestive system, and if dissected, you can actually see what the worm ingests

6. The earthworm's setae are tiny bristle-like structures found on it's skin. These are very helpful in the movement of the worm, and they protect it by spiking out in soil to prevent any predators from grabbing it away from its habitat ( since my camera couldn't take a nice picture of the setae, i was able to find a species of worm with very visible setae)

7. The earthworm's crop stores the worm's food as it comes in through the esophagus, and the gizzard grinds it down until it is ready to be digested. This process of storing and grinding food makes the worm very well adapted to its environment ans explains why it can extract its food from the soil.

8. Past the 32nd segment of the worm,I would see the continuation of the digestive system, as well as more nephridia. I would also see the worm's food, mostly made up of detritus and soil.

9. Once earthworms begin to reproduce, they begin to attach themselves to one another and exchange their sperm, Since all earthworms are hermaphrodites, they collect the sperm and contain it in special sacs to be used once the eggs are mature. Once this happens, the clitellum begins to secrete a sticky substance in the form of a ring which is released with the eggs and sperm. This in turn creates a cocoon, which contains the now fertilized eggs.(The picture shows the seminal vesicles, which create the sperm needed for reproduction)

For our classes first major dissection, we were assigned to dissect an earthworm from the phylum Annelid. It was definitely one of the more exciting things we've done in our biology class, and one of the best dissections I've had yet, as odd as that sounds. Being a fairly visual learner, I found the dissection to be really informative, and quite the experience. We began with the pinning of the worm to the dissecting table, which brought more than a couple of squeals from my classmates, but it was easily done. The real work came when we had to make the major incisions. We cut down the length of the worm's dorsal skin, exposing all the organs and body parts that the earthworm had. Pinning the skin to the side, we started to view the various organs under the microscope, like the intestine and the worm's multiple hearts. Definitely the most disgusting part was when we viewed the bottom  half of the worm, which for us, contained the intestine, typhosole, and  the earthworm's diet of soil and decaying matter. The brown-black mess was eventually moved away as we wanted to view the worm's intestines in it's entirety. Once we were done, we spent a good amount of time cleaning up the various scalpels, pins, tweezers etc. and getting pieces of worm off of every surface that was visible. In the end, the dissection was a truly interesting experience, and i definitely helped us actually see what was inside of what we were learning about, not just be looking up diagrams of it in out textbooks and on the internet. This hands on experience makes what we're learning about that much more interesting and special.

Flatworms from around the ocean

Genus	Eurylepta
Species	sp.
Family	Euryleptidae
Order	Polycladida
Location	Shimoda, Izu Peninsula, Sagami Bay, Japan
Length	about 6 mm
Depth	intertidal
Date	August 24, 2002

Genus	Pseudoceros
Species	sp. 2
Authority	Newman & Cannon, 1998
Family	Pseudocerotidae
Order	Polycladida
Location	Solitary Island, Coffs Harbour Region, New South Wales, Australia

Genus	Pseudoceros
Species	dimidiatus
Authority	von Graff, 1893
Family	Pseudocerotidae
Order	Polycladida
Location	Kailua-Kona, Hawaii