Annelid Dissection!

On Friday, in conjunction with our lessons on the anatomy of annelids, the entire class was was involved in a worm dissection lab. This was all done for the sake of observation, to understand the works of digestion, and more interestingly, sexual reproduction. Differentiating between the dorsal side of a worm and the ventral side are important when we consider worms, as is the relationship between the external and internal parts of the worm. While the worm may appear primitive, it's very surprising to see how many functions it contained! It was very exciting to handle the organism like a surgeon, trying to be as neat and quick as possible--even incisions are an art, I suppose. The setae we studied in the textbook appeared even smaller and sparser under the microscope, little silver hairs on a mound of pink flesh. The food digesting inside the dead worms appeared as watery dirt. Even the Clitellum was much more subtle as a real specimen than in a diagram. Compared to scientific diagrams, our worms were raw but red in flesh, but I was very proud of the work I did-- the pinning which was enjoyable as well, like I was creating an undead diorama. However, beyond my interest, I learned that annelids had very definite organs and many adaptions: how externally, sperm grooves and setae, like grips on the rungs of ladders, will help with transferring sperm and also traction for movement, but also how internally, a cut on the dorsal blood vessel would be so fatal to the worm because it is so important and one large part of the circulatory system. Worms also have a digestive system kind of similar to our's, where food goes through an esophagus and intestine, though we lack gizzards.
Unfortunately, my partner and I could not upload the phone photos onto the computer, however I made due with Nathan's, thank you Nathan. Earthworms are oligochaetes and this makes me curious about what it might be like to dissect a polychaete. This lab was  very hands-on and there is nothing I'd rather do for a period than look at things under a microscope or taking photos, so I was lucky to do both. I would recommend all courageous Biology classes to step up to the B.C. standards and do this lab. Here's an idea of what it looks like: http://www.youtube.com/watch?v=u9HHS1uPFSo

1. What is the name of the pumping organs of an earthworm?
They are called the aortic arches, which are hearts, although
they do not contain valves and chambers.

2. Trace the parts of the digestive tract?
The food passes through the pharynx and
passes through the esophagus, then the crop
and the gizzard and finally through the
intestines.

3. Which parts of the earthworm serve as its brain
The brain is above the pharynx and connected
to the ventral nerves; it is firmly attached 

4. Which parts of the worm/excretory system?
The excretory system goes hand in hand with the
digestive system above. However, a pair of nephridia
in literally each body segment helps remove waste

5. How can you find out whether an earthworm eats soil?
Put it in soil and examine its excrement in a glass jar. Try
adding different things in soil (rotting vegetables, dead
animal corpses, fertilizer). Since earthworms live in the
earth, its also logical to assume that everything
they eat exists in the soil. 

6. What are Setae? Well, they aren't as grey and silver
as I thought. They are like little black stubbles.
Setae are the small bristles that are good
for brushing against the soil, basically, providing
traction in the soil.

7. Highlighted in green are the special organs that
help take in small amounts of soil from large amounts of
food. The gizzard mashes the food while
the churned-up products are moved to the intestines,
so it's a continuous process. Also, their mouths
don't shove in a continuous amount of dirt, I assume
they can close.

8. Why didn't we go past segment 32? As you can see
fromt he worm already, tons of digesting food and faeces
in the making are visible. The lower we go, the more
dirty gooky stuff we'd see, perhaps dangerous things
that could be breathed in by our noses.

9. These worms are having the time of their lives. I'm
not sure if I was supposed to keep the paper or just post
all my findings on a paragraph online, but I'll do both, in
the honour of vertebrates everywhere.
It's important to remember that worms are hermaphrodites
so they have both MALE GENITAL PORES and
FEMALE GENITAL PORES. Sperm is produced from these pores
and it transfers to the female pores., which also produce pheromones.
Both these pores are located within one segment of each other.
According to cronodom.com, the sperm are transferred
along SPERM GROOVES through the muscle spasms during
worm sex. After going inside the female genital pore of another worm, the
sperm goes the OVARIES, where the eggs are stored. Again, the
ovaries are only within one segment away from the female
genital pore. In conclusion, the multiple sperm pores
on a worm compared to the single female genital pore makes it
easier for one worm to transfer genetics, taking three times
shorter, I suppose. Due to the close proximity of these pores
and grooves, this sexual reproduction can also be
done more conveniently.