Perch Dissection Lab by Z9GNF2Q

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									Perch Dissection Lab
Life Science
Name _____________________________________

INTRODUCTION:

In this dissection lab, you will be using the perch in order to study the class
Osteichthyes. The yellow perch, Perca flavescens, is a common fish found in
freshwater lakes and streams and is oftentimes foraged upon by game species, such as
northern pike, bass, and walleye. It serves as an excellent representative of the bony
fishes, as it possesses all characteristics common to the group. Amongst the
adaptations allowing for great diversity and success amongst Osteichthyes, you will
note a bony endoskeleton, four pairs of gills, a lateral line system, a swim (or gas)
bladder, and a variety of fins, each with specific functions. As 95% of all fish
species are classified as ray-finned fishes in the class Osteichthyes, this group
represents the most diverse class of vertebrates in our taxonomic system.

CLASSIFICATION:

    Kingdom:   Animalia
    Phylum:    Chordata
    Class:     Osteichthyes
    Genus:     Perca
    Species:   flavescens

EXTERNAL DISSECTION:

Examine the external anatomy of the perch and identify the major subdivisions (head,
trunk, and tail) and parts of the body. Before proceeding with the next activity,
complete a drawing of the external anatomy of your perch, including the following
structures in your drawing:

_____   Anterior dorsal fin          _____   Maxilla
_____   Posterior dorsal fin         _____   Mandible
_____   Caudal fin                   _____   Operculum
_____   Anal fin                     _____   Eyes
_____   Pelvic fin                   _____   Scales (note the annuli, or growth rings)
_____   Pectoral fin                 _____   Anus
_____   Nostrils (nares - 4)         _____   Urogenital opening (eggs, sperm & urine
_____   Lateral line                         exit through this opening)
_____   Tongue (not a taste organ)




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After finishing your drawing, complete the following activities prior to proceeding with
the internal dissection of your specimen:

** Remove the eight fins. As each one of them is removed, note the function below:

       a.   Anterior dorsal fin: _____________________________________
       b.   Posterior dorsal fin: _____________________________________
       c.   Caudal fin: ____________________________________________
       d.   Pectoral fins (one pair): _________________________________
       e.   Pelvic fins (one pair): ___________________________________
       f.   Anal fin: _____________________________________________

** Scales -- The scales are made of the same material as the fingernails of man.
Remove a few scales and observe them with a dissecting scope. Using the dark rings,
or annuli, estimate the age of your perch. _____________________

** Gills – Cut away the operculum from the left side and examine the gills. Cut away
one gill arch, place it in water, and examine it with a dissecting scope. The spaces
between the gills are called gill slits, or gill clefts. Sketch the gill that you observed in
the space below:




               Be sure to label the gill filaments and gill slits!


INTERNAL ANATOMY:

Hold the fish with the ventral side up and the head pointing away from you. Insert
the point of your scissors through the body wall in front of the anus and cut up the
midline of the body to the space between the opercula. Now, lay the fish on its right
side (with the head on your left) in the dissecting pan. Continue to cut up around the
back edge of the gill chamber to the top of the body cavity. Make another incision
from the starting point of the ventral incision close to the anus and cut upward to the
top of the body cavity. Be careful not to disturb the internal organs. With a scalpel,
remove the whole lateral body wall by cutting along the top of the body cavity. This
procedure will expose the body organs in their normal position.




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Once you have successfully opened your specimen, locate the following structures.
Complete a drawing of the internal anatomy, making sure to label each of the
structures on your sketch. YOU WILL NEED TO PROCEED IN THE ORDER IN
WHICH THE STRUCTURES ARE LISTED BELOW. This is very important in order for
you to locate all internal organs!!

_____   Trunk muscles
_____   Vertebrae
_____   Ribs
_____   Liver
_____   Gallbladder (stores bile used in digesting fat)
_____   Stomach (cut it open and see what’s inside!!)
_____   Spleen (attached to mesentery of stomach; destroys worn out red blood cells)
_____   Pyloric caeca (attached to intestine)
_____   Intestine (Note the fat surrounding this structure)
_____   Esophagus

Once the above structures have been identified, remove the entire alimentary canal
(esophagus, stomach, intestine). This will allow you to examine the remaining internal
organs:
_____ Ovaries (between intestine and swim bladder) or testes (below air bladder)
_____ Swim (air) bladder: REMOVE BEFORE PROCEEDING!
_____ Kidneys
_____ Urinary bladder

To finish the required portion of the internal section, make a horizontal cut through
the anterior wall of the body cavity in front of the liver. This will expose the two-
chambered heart. The heart consists of a light-colored ventricle and a larger thin-
walled atrium.

_____ Two-chambered heart

OPTIONAL DISSECTION:

Hold the fish with the dorsal side up and the head pointing away from you. Using your
scalpel, cut the skin from the skull and scrape the skull carefully to wear away the
bone. When the bone is very thin, pick out the pieces with your forceps to expose the
brain. Locate the olfactory lobes in front, the larger lobes of the cerebrum behind
these, and the very thin optic lobes posterior to the cerebrum. The cerebellum is
posterior to the optic lobes, and the medulla is the enlargement where the spinal cord
joins the brain.

                  (Five points extra credit for a successful removal!!)




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NOW, FOR THE QUESTIONS….

1. List at least three adaptations of the bony fishes that allow them to survive
   successfully in an aquatic environment.
   ___________________________________
   ___________________________________
   ___________________________________

2. How does the anterior dorsal fin of the perch differ from the posterior dorsal fin?
   _________________________________________________________________
   _________________________________________________________________

3. What is the name of the structure that covers and protects the gills?
   ______________________________

4. What is the name of the pigmented cells that give the fish its color pattern?
   ________________________________

5. What is the lateral line system AND how does it work?
   _________________________________________________________________
   _________________________________________________________________

6. The mucus-producing epidermis of the fish serves what TWO functions?
   _____________________________________________
   _____________________________________________

7. The three pyloric caeca serve what function? ____________________________
   _________________________________________________________________

8.   What three gases are found in the swim bladder? ________________________

9.   What does the swim bladder allow the fish to do? ________________________

10. Does the perch have an open or closed circulatory system? _________________

11. How many chambers does the heart of the fish have? ______ What are they
    called? __________________________________________________________

12. Describe the role of the gills and gill filaments in the respiratory system of the
    fish. ___________________________________________________________
    ________________________________________________________________
    ________________________________________________________________
    ________________________________________________________________




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13. The brain of the perch has five paired lobes. List them below and provide the
    general function of each lobe:
    _____________________________________
    _____________________________________
    _____________________________________
    _____________________________________
    _____________________________________

14. Are bony fishes monoecious or dioecious? ___________________________

15. Do perch employ internal or external fertilization? __________________

16. To what class do the sharks, skates, and rays belong?
   _____________________

17. To what class do the lampreys and hagfish belong?
   ________________________




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