1. Phylum Chondrichthyes
Shark Dissection
Phylum Chondrichthyes

2. Dog Fish Shark
Scientific Name: Squalus acanthias Common Name: Spiny Dogfish

3. (I.) Background Information
The Spiny Dogfish, or Squalus acanthias, or Pacific Dogfish, belongs to the subclass Elasmobranchii and is abundant from southern California to the Gulf of Alaska. Its habitat includes cool waters near the coast. Dogfish are usually active and pursue smaller fish or even squid and pelagic crustaceans to supplement their diet.

4. (II.) External Anatomy Procedure: Step 1
Run your hand along the shark's body, from head to tail and vice versa. Notice the difference in texture. The abrasiveness that you feel are the sharks scales, called placoid skills (also called the dermal denticles). Use a razor to remove a piece of skin, examine under a microscope. Draw the skin using the second objective.

5. (II.) External Anatomy Procedure: Step 2
Next, identify all the major external parts: snout, nostril, mouth, eye, spiracle, gill slits, anterior dorsal fin, pectoral fin, pelvic fin, second dorsal fin, claspers (male only), posterior dorsal fin, cloaca, caudal fin, and lateral line. Pin each of the above and text a picture to Ms. Brown along with group names (on first text only)
(In nature, there is additionally one more part, called the Fin Spine, but it is slightly poisonous so fittingly it was removed prior to the arrival to our classroom.)

6. (II.) External Anatomy Procedure: Step 3
Carefully using a probe to open the mouth, run your finger along the inner jaw line to feel the teeth.
Describe how they feel, their placement, shape and approximately how many there are.
Describe the placement of the mouth in relation to the head, and eyes.

7. (II.) External Anatomy Procedure: Step 4
Determine the sex of your shark. How do you know?
Record the following measurements of your shark:
Tip of snout to tip of caudal fin
Tip of snout to orbital socket
Tip of snout to front of pectoral fin
Tip of snout to base of caudal fin
Length of pectoral, dorsal and caudal fin base to tip.

8. (II.) External Anatomy Procedure: Step 5
Take a moment to investigate the Sting Ray
Complete the same external investigation that you did on the shark (patch of skin needs to be from the ventral side of the Sting Ray)
Measurements need to be from the snout to the base of the caudal fin, and from tip to tip of the pectoral fins.
Measure from snout to last gill slit.
Complete Step 2, and 3 for the Sting Ray

9. Day 2 Internal Anatomy Procedure: Step 1
Place the shark ventral side up.
Remove the staples on the ventral side of the shark. Be careful to not cut yourself.
Using scissors continue to create an I cut down the center of the shark. Be careful not to cut too far into the shark, make just a shallow cut through the skin. Cut from the pelvic fin to the pectoral fin.
Then, cut across the shark at the pelvic fin and again at the pectoral fin.

10. Day 2 Internal Anatomy Procedure: Step 2
Use the "flap” to open up to the internal organs. Pin the flap back if necessary.
Identify the liver in the shark. How many lobes does it have? Describe its texture, and color. What is it’s function?
How is the liver attached to the body? Using scissors cut the liver attachment so it can be removed from the body.
Remove all the lobes.

11. Day 2 Internal Anatomy Procedure: Step 3
Using the available scales in the room, weigh the shark liver on a paper towel.
Using the available large scale in the room, weigh the whole shark (your weight minus the shark)
Calculate the percent of mass that the liver weighs. How does this compare to humans?
Cut a ½” section off a lobe. Describe the tissue. Describe how form fits function for the liver?

12. Day 2 Internal Anatomy Procedure: Step 4
What would you expect if the piece you cut off was placed in a beaker of water. Hypothesize.
Place the piece(s) in a cup of water. Describe the reaction. Why?
Cut another piece off the liver and see if you can get any oils out of it.
Put the oils in a cup. What happens? How do these oils help sharks who have no swim bladder?

13. Day 2 Internal Anatomy Procedure: Step 5
Locate the following internal organs and pin and identify them.
Take a picture and send it to Ms. Brown
Esophagus, Spleen, Pancreas, Gall bladder (may be with your liver) Pyloric Stomach, and Cardiac Stomach, Duodenum, and Uterus.

14. Day 2 Internal Anatomy Procedure: Step 6
Locate the Uterus of your shark. All sharks should be pregnant.
Using a razor slowly cut through the thin external sac of the uterus to reveal any eggs or developed offspring.
Describe what you see immediately after opening it up (before removing anything).

15. Day 2 Internal Anatomy Procedure: Step 7
Remove any eggs or developed eggs from your uterus.
Describe the development of each.
What are they attached to? What is that analogous with on humans.
When the food supply is almost gone they will be ready to leave the uterus. How far developed are they? (Dogfish Sharks do have live birth).

16. Day 2 Internal Anatomy Procedure: Step 8
Using a razor make a slit in the Cardiac stomach down to the Pyloric Stomach.
Open it up and describe what you see. Any food?
Describe the lining of the stomach? How does form fit function?

17. Day 2 Internal Anatomy Procedure: Step 9
Follow the digestive tract down to the spiral intestines.
The intestinal style is unique to the animal kingdom. Use the sharp point of a razor to carefully cut into the spiral intestines. Scissors may also be helpful.
Describe what you see? How does the food get through? What is beneficial for this type of intestine? How does form fit function? How does it compare to human intestines?

18. Day 3 Internal Anatomy Procedure: Step 1
Locate the gills of the shark. Run your fingers through the gill slits. Describe what it feels like? How many are there?
Using a knife cut a square out of the gills. What do you notice while cutting this area?
Be able to describe or sketch the inside of the gills. (done as part of the shark questions)
Where is the water coming in, and where does it leave from? (draw arrows on your diagram)

19. Day 3 Internal Anatomy Procedure: Step 2
Using scissors continue the previous I cut up to just below the jaw. Be sure to create the top of the I and cut side to side under the jawline.
Pin back the tissue and locate the inner side of the gills. Describe their connection with the mouth.
Locate the spiracle on the external side. What connection to the gills does it have?
How does the esophagus transverse through the pharynx area?

20. Day 3 Internal Anatomy Procedure: Step 3
Locate the heart and using scissors cut any connections it may have holding it in the body, and remove it.
Use a razor blade and make a single cut straight through the heart, into two halves to reveal the chambers.
Describe the similarities and differences between a shark and a human heart? Ventricles? Aorta? Atrium? Heart valves?

21. Day 3 Internal Anatomy Procedure: Step 4
With the shark dorsal side up, locate the area on top of, and at the tip of the snout.
Use a magnifying glass to look for the very small pores called the Ampullae of Lorenzini.
Describe the pores, size, spacing, and location.
Gently squeeze the area and describe what happens.
What is the function of this area, and how does it help them become a formidable predator?

22. Day 3 Internal Anatomy Procedure: Step 5
With the shark dorsal side up, locate the area on top of the head where the brain would be located.
Use a razor to ‘score’ a medium sized square on top of the head between the eyes.
Use a knife to cut through the skull on the lines you scored with the razor.
Remove the skull in that area. Describe the brain. What shape is it? Texture?
How does it compare to humans? 2 hemispheres? Gyri and sulci?

23. Day 3 Internal Anatomy Procedure: Step 6
Using scissors carefully remove the tissue around the eye.
Describe the muscles surrounding the eye. Try to locate the white 3rd eyelid (nictitating membrane) Describe its location, and its texture. How does form fit function?
Remove the eye from the socket. Describe the eye itself. What does the pupil look like?
Using a razor, cut straight down the eye, seperating it into a 1/3 section in the front, and 2/3 section in the back.

24. Day 3 Internal Anatomy Procedure: Step 7
Using a razor, cut straight down the eye, separating it into a 1/3 section in the front, and 2/3 section in the back.
Explain how the fluid in th eye could help the shark’s eye.
Cut through the front section with scissors or razors and locate the lens. Describe its shape, and structure, and how it’s function fits its form.
Show myomere in front slides (ignore this)

25. (IV.) Functions External Parts and Functions
Caudal Fin: Allows shark to change direction and aids in movement.
Claspers: Found only on male sharks, they enable the transfer of sperm to the female during mating.
Eye: Shark is able to see its surroundings.
First Dorsal Fin: Allows shark to change direction and aids in movement.
Gill Slits: Water passes throught the slits effectively allowing the shark to breathe.

26. External Parts and Functions
Lateral Line System: Actually in the interior of the shark but visible from the outside, it helps the shark detect electromagnetic energy, aiding in pursuit of prey.
Mouth: Food and water pass through to the body.
Nostril: Allows shark to smell.
Pectoral Fin: Allows shark to change direction and aids in movement

27. External Parts and Functions
Pelvic Fin: Allows shark to change direction and aids in movement.
Second Dorsal Fin: Allows shark to change direction and aids in movement. Snout: Front of sharks head.
Spiracle(s): These are two openings behind the eyes. They allow water to pass through, allowing the shark to stop moving.

28. Internal Organs and Functions
Gall Bladder: used in urination process.
Heart: pumps blood to other areas of body.
Kidney: removes wastes from blood.
Liver: Large organ which cleanse blood and stores bile.
Pancreas: Produces digestive enzymes for transport to the spiral intestine.

29. Internal Organs and Functions
Rectal Gland: Stores solid wastes for excretion out of the body.
Spiral Intestines: Absorbs food for the shark to utilize as energy.
Spleen: Associated with the digestive system, the spleen is actually part of the circulatory system. Stomach: J-shaped organ which digests (breaks down) food.
Vas Deferens: Duct which transports sperm from testes to claspers.