Dogfish Shark Dissection Notes
We had the students put a glove on one hand only, so that they
could use one hand to touch the shark and use the other hand to write.
We told the students they were welcome to touch the shark, but were not
required to touch it if they did not wish to do so.
We first explained that the school had obtained one shark for each
class to inspect. The sharks were not living, and had been preserved for
shipment to us. Each shark was separately wrapped, and has been slit
open so that we could review its internal organs. The “ coloring” they
notice is dye that was inserted in the shark so we could see its different
organs. The packaging of the shark will indicate if it is a male or female.
(The male shark will have “ clasper” pelvic fins.)
External Observation:
1. The students rub their finger along the skin of the shark. How
does it feel to them? We talked about the sharp scales that
make up the shark’ s skin. It is often compared to sandpaper.
2. Fins: We found it most helpful to use the resource sheet that
has a “ side view” of the shark, and clearly designates the fins.
When talking about how the fins help with the shark’ s
movement, one student compared the fins to wings on a plane.
We also talked about the rudder of a boat.
3. The lateral line can be seen clearly along both sides of the
shark. We talked about how this lateral line helps the shark find
prey in the ocean. We talked about what the word “ prey”
means. Although the shark can see with his eyes, the water can
be deep and dark and this lateral line helps him locate objects
such as prey.
4. When examining the gills slits, the parent would hold the shark,
and the group would count the slits on each side of the shark.
5. When examining the teeth, the parent held the shark and pried
open the mouth of the shark so the students could see the rows
of the teeth, the shape of the teeth, and the tongue. The tongue
might be difficult to see, but there does appear to be a flap of
flesh which can be seen on the bottom of his mouth. We pointed
out that the shark has multiple rows of teeth. We also talked
about how the teeth are very sharp and are used to “ shred”
food. The shark does not chew its food like we do. The shark
will also swallow its food whole. This may be seen in the
contents of its stomach!
6. We examined the shark’ s face, pointing out the eyes, nostrils
and spiracles. We discussed how the spiracles were a special
type of “ gills.”
7. We held up the shark and asked the students to tell us about the
shark’ s shape. We heard words such as oval, submarine,
torpedo, airplane - - and then we talked about how this type of
shape helped the shark move quickly in the water.
8. We talked about the nostrils (nares) and how the shark’ s sense
of smell helps him recognize chemicals in the water such as
blood. If there is an injured fish nearby, it will locate it quickly.
Internal Observation:
The shark arrived already slit open (ties needed to be cut) but
it was necessary to make the slit larger in order to see the heart
near the head of the shark, and the rectal gland at the end of the
intestine.
When opening the shark, it is necessary to “ pull out” the
large liver lobes, so that all the organs can be seen. What seemed
to work best was to have the students examine all the organs before
answering the individual questions on their lab sheet.
1. Heart: This organ is located near the head of the shark. It is
small and does not perform as many functions as a human heart.
2. Liver: This organ is large and consists of three lobes. It
produces bile --- a substance that aids in digestion. It also
stores fat and oil, and thereby provides buoyancy for the shark.
3. Gall Bladder: This organ is located on the upper left side of the
shark under the liver. It stores bile from the liver.
4. Stomach: This organ appears in the mid-section of the shark.
It may be large and protruding or narrow and flat. (We found
entire fish remains in the larger stomach organs!) We opened
the stomach at the end of the lab and gave the entire class the
opportunity to see what was found inside.
5. Spleen: This organ has sort of a triangular shape and is located
at the tip of the stomach organ. The spleen is a site of blood
formation for the shark.
6. Pancreas: This organ was located on the underside of the
stomach near the top of the intestines. The pancreas produces
digestive enzymes.
7.
8.
9.
Intestines: This organ extends from the stomach to the pelvic
area of the shark and is tube shaped. This organ is used in
digestion and nutrient absorption.
Rectal gland: This is a small gland located in the lower left area
of the shark, near the end of the intestines and the pelvic fins.
This gland is used for the production of waste.
Cartilage: The shark does not have bones, only cartilage. You
can particularly see this at the caudal fin area where the fin has
been partially severed from the shark’ s body. We talked about
where you can find cartilage on a human body.