Download Dogfish Dissectionproc17

Anatomy Dogfish
Dissection
PROCEDURES 2017
Objective: The Spiny
Dogfish is a small,
Do
not
write
on
this!
cartilaginous fish that has
long been a popular
specimen for study in the
Zoology. Its
popularity is due to its large numbers and consequent ease of capture in the sea,
convenient storage, and representative anatomy of primitive jawed fish. We are
also able to use this in anatomy to discuss the differences in digestive systems of
the shark and human. This is an extremely important lab grade. It is
approximately 15 percent of your semester grade. You need to do a good job on
this! Choose your partners wisely (you will need to work in groups of 4 or 5); if
you have an unexcused absent during this time period it will count against you!
The due date will be posted on line. I will ACCEPT ANY LATE WORK (only up
to one week past the due date) on this assignment, but you will lose half credit.
That means the best you can get is a 50 percent on your lab. Even if the lab is
handed in the following morning.
Procedures:
1) You will work in groups of four or five. This is due to the extreme expense
of the specimens. You may discuss your definitions with your partners, but
you may NOT COPY the definitions word for word. IF YOU COPY
FROM A PARTNER; YOUR WHOLE GROUP WILL RECEIVE A 0.
You will need to type up your definitions. You may want to split up the
sections to make sure everyone is working and the lab is completed. The
terms must be in your own words. I will also be grading you on
participation. Your partners will also decide whether you deserve full credit
or not.
2) Now it is time to receive a stinky, oily sharky to play with. You will also
receive a garbage bag to store your shark. Do NOT throw this away at any
point during the lab. You will need this bag for the entire dissection. I do
NOT have any extras.
3) The first thing we will do is to compare the anatomical structure of the shark
and the human. Place your specimen on a dissecting tray and examine its
external features (USE THE HANDOUTS TO FIND THE NAME AND
FUNCTION OF THE STRUCTURES). Note that its shape is streamlined,
enabling it to glide easily through the water with the least possible
resistance. The body is divided into three anatomical regions: the head,
which extends from the tip of the snout to the pectoral fins; the trunk, which
continues to the origin of the tail; and the tail, which is at the posterior end.
4) Draw, label and tell me the function of the following features: Caudal
Dorsal Fin, Cranial Dorsal Fin, Caudal Fin, Dorsal Spine,
Endolymphatic Pore, Placoid Scales, External Gill Slits, Eye, Eye Lid,
Interbranchial Septum, Lateral Line System, Mouth, Naris, Pectoral Fin,
Pelvic Fin, Spiracle, Claspers (on males only) and Spiracular Valve.
Answer the questions on sharks on your observation sheet. Make sure
these are in your own words and don’t copy from your partner. Remember to
answer the question in the observation section in your own words.
5) You will be taking measurements of your shark before you cut the shark.
What parts you need to measure are located in the table on your observation
sheet; most of you will not have a dorsal spin (if it is not present simply record
NA in the box). When I ask you to measure the caudal and dorsal lobe, that is
referring to sections of the caudal fin. Make sure all measurements are in
centimeters. The actual measurements are recorded on your observation sheet.
Reproductive structure
5. Next you will determine the sex of your dogfish (Record this on your
observation sheet). Do this by flipping your shark so its ventral side is facing
up, and now look between the pelvic fins. Use the diagrams in the shark packet
“External Anatomy” to help identify the sex of your shark. You only draw,
label and define the sex of shark you are dissecting. You will need to draw,
label and give me the function of the following parts:
Male: anus, clasper, cloacal aperture, pelvic fin, and urogenital papilla.
Female: anus, cloacal aperture, pelvic fin, and urinary papilla.
Yes, some of these anatomical parts are repeated from your external anatomy
section. Label them, but you do NOT have to define them twice.
Muscular structure (CUT #1)
6. Follow the procedure below to skin your shark. You will draw the muscles
that you see. You will need to label and give me the function of the following
muscles: craniomaxillaris, preorbitalis, epihyoideus, coracohyoideus,
branchial muscles, hypobranchial muscles, ventral longitudinal bundle,
lateral longitudinal bundle, dorsal longitudinal bundle, intermandibulari,
levator palaoquadrati, levator hyoideus, cucullaris, and dorsal constrictors.
ONLY SKIN YOUR SHARK ON ONE SIDE!!!! To view them, remove a strip
of skin from one side of the dogfish. You will begin on the dorsal midline
cutting caudally from the Caudal Dorsal fin toward the Caudal Fin. This may be
done by making a shallow incision. You will gently peel away the skin; be
careful to not rip off the muscle (the skin is only 1/16 of an inch thick). Remove
the skin all the way to the ventral midline of the shark. You will have removed
all of the skin from the top of the shark towards the bottom and all the way back
towards the tail. BE CAREFUL NOT TO PUNCTURE INTO THE
INTERIOR OF THE SHARK!
Explain to me how a shark (or any fish) for that matters moves. This is done
in the conclusion section.
INTERNAL ANATOMY (CUT #2)
WARNING: BONES AND TEETH ARE VERY SHARP. BE CAREFUL
BECAUSE IT IS EASY TO CUT YOURSELF.
7. In order to expose the coelom (internal body cavity), the body wall must first be
dissected. To do this, follow the procedure below(use the place mat as a guideline,
blue dotted line):
- Place your specimen on a tray on its back to expose the ventral side.
Using sharp scissors make a shallow incision through the skin layer from
a point immediately cranial to the cloaca. Now cut cranially to the
pectoral girdle slightly to the left of the midventral line (use Fig. 4.1 in
your “Internal Anatomy” handout as a reference). It is important to avoid
cutting along the midline near the pectoral girdle in order to prevent
damage to underlying structures. Now cut through the muscle layer by
making a deeper incision along the same path as the first incision through
the skin.
- Carefully extend the incision made above from the coracoid bar of the
pectoral girdle to the level of the second gill slit. Cut through the body
wall, but do not cut deeply.
- Make a transverse incision through the body wall about midway between
the pectoral girdle and the pelvic girdle. Extend the cut on both sides to
the lateral line.
- This WILL BE MESSY because of the oils found in the shark’s liver.
Do not remove the flaps of skin so you can store your shark. When you
are done with this cut, you may want to wrap the shark with paper towels.
8. Draw, label and define the following: Cloaca, Duodenum, Gall bladder,
Heart, Liver, Pancreas, Pericardial Cavity, Spleen, Stomach, Transverse
Septum, Uterus (only in females), anterior intestinal vein, anterior intestinal
artery and Valvular Intestine. If any of these terms are repeated you will not
need to define them twice.
ORAL CAVITY: (CUT #3) The mouth or oral cavity is the space between the
external ridge of the teeth and the internal opening of the spiracles. To view the
oral cavity, follow the procedures below:
-Begin the incision by cutting through the left corner of the mouth. BE
CAREFUL YOU WILL BE VERY NEAR THE EXTREMELY SHARP NASTY
TEETH OF AN OVERLY AGGRESSIVE SHARK!!! IT HAS MUSCULAR
REFLEXES, WHICH MAY CAUSE THE JAW TO SHUT
UNEXPECTEDLY!!!
9. (USE SCISSORS NOT A SCALPEL) Continue this cut through the Meckel’s
cartilage, cartilages of the branchial arches and the hyoid arch. Look at figures
5.1(In the Digestive and Respiratory Handout) for a reference. Draw what you see
on the observation page. You will need to label the following features and give
their functions: tongue, teeth, , esophagus, Meckel’s cartilage, gill raker, gill
filaments, interbranchial septum, branchial vessels, papillae, coelom and the
pharynx.
10. Examine the digestive tract of the shark. Most of the structures you have
already seen, but I would like you to draw and label only the digestive tract. Use
figure 5.5 as a reference. It is on the last page of the “Digestive and Respiratory
Systems”. Explain to me how the digestive system of a shark works (5 to 8
sentences answered in your conclusion section. Also, explain to me how a
dogfish feeds, what it feeds on and how it replaces teeth. You will have to
google the second part of this section. You may cut into the stomach and
intestines to see if the shark has eaten anything.
11. You will now view the internal structure of the heart. The heart must be
removed in order for it to be viewed. Cut the attachments of the sinus venosus to
the transverse to the transverse septum. Now cut through the ventral aorta near its
union of the fourth and fifth artery. Once the heart is removed you will draw a
picture of the interior of the heart. You will need to label all the parts, but you
only need to tell me the function of the following: atrium, ventricle,
atrioventricular valve and the conus arteriosus.
Explain to me how a shark circulatory works in five to eight sentences. There is
room to do this on your dissection sheet.
12. Now you will look at the brain from the dorsal aspect. Remove the skin and
other tissues from the dorsal surface of the head and around the eye. Carefully cut
away the dorsal portion of the chondrocranium to expose the cranial cavity. You
do not need bone cutters, scissors and scalpel should be fine. Continue to expose
the brain by removing the supraorbital crest. Draw and label what you see. Give
me the function of the following parts of the brain: Cerebral hemisphere,
olfactory bulb, optic nerve, hypophysis, epiphysis, telencephalon,
prosencephalon, mesenscephalon, rhombencephalon, myelecencephaln,
metencephaln, tectum, medulla oblongata, and diencephalon. Some regions and
functions will overlap, this section can get tricky I can help you with it.
I would like for you to describe the senses of a shark; how it finds it food and
detects it surroundings.
13. Finish your dissection by examining the ear of the shark. First locate the two
endolymphatic ducts near the dorsal midline between the spiracles. Scrape the skin
away from this region. Next slice the cartilage away in the thing sections until you
can see the inner ear through its transparency. Label and give me the function of
the following: utriculus, anterior semicircular duct, crista, ampulla, external
spiracular pore, sacculus, horizontal semicircular duct, and posterior
semicircular duct.
14. Make sure everything is clean, tray as well as your dissection kit.