Moore, Timothy
Moore, Timothy
Instructor: Mrs. Tammy Moore
Class: VHSG Online Biology
15 July, 2008
PERCH DISSECTION
Examination of a representative organism from class Osteichthyes and subphylum Vertebrata.
Abstract
Perch are representative organisms of the class Osteichthyes. Through careful observation, I analyzed
perch body structures to learn more about vertebrate anatomy. I found that perch exhibit certain
characteristics that are common to all vertebrates and some characteristics specific to the class
Osteichthyes.
Introduction
According to Dr. Jay Wile (2002) [1], the perch is a representative organism for the class
Osteichthyes (bony fish). The members of class Osteichthyes have an interesting internal structure that
is ideal as an introductory lesson in anatomy. Their internal structure is complex enough to point out
some features common to all of the other members of subphylum Vertebrata which I will study this
year. At the same time, however, their internal structure is not so complex that it becomes
overwhelming, as is the case with many vertebrates.
In this lab, I gained a better understanding not only of perch anatomy but also vertebrate
anatomy in general. I observed features that are obviously unique to perch or class Osteichhyes and
hypothesized why did this class or species develop these features? I also recorded, through annotated
digital images taken during the dissection, structures for later reference for comparative anatomy with
other vertebrates in future dissections. Observations and images were gathered directly as well as via a
hand lens and microscope. I took the time to think about how the structures I observed contributed to
the organism's survival. By observing, recording, and thinking about the structures of the perch, I
learned about this interesting organism's anatomy.
Moore, Timothy
Since this lab is designed as an introductory dissection to the vertebrate subphylum, it will be
interesting to compare and contrast the perch to other organisms in this subphylum that will be
dissected later. How do perch gills compare to lungs? How similar in structure are organs common
between the perch and other vertebrates such as the liver, brain, and gall bladder?
Methods and Observations
External Anatomy Observation:
Typical to the standard procedure for dissecting an organism, the perch external anatomy was
observed first. A diagram of perch anatomy was used to aid in labeling the various observable
structures. Below is an annotated image of my dissection specimen that includes the addition of these
labels.
[insert annotated perch external anatomy picture here]
Next, I closely examined the structures of the perch mouth. The structure of the mouth was
[insert observations here].
The teeth were observed. Their structure was [insert observations of the perch teeth]
[insert annotated mouth images here]
Next, I examined the tongue. The tongue is attached [insert observations here]
[insert annotated tongue imge here]
Next, I examined the fins of the perch. Fins can be supported by one of two structures: rays or
spines. If the structure bends it is a ray. If it does not bend, it is a spine.
Moore, Timothy
[insert images of fins with identification of whether they contain spines or rays]
Next, I began examining the scales of the perch. I noted that the attached scales had the
following characteristics: [insert characteristics]. I then detached a scale for closer inspection under a
hand lens and microscope. [insert observations and images].
According to Dr. Wile [2], in the live fish, the body would be covered by mucus. The mucus
waterproofs the scales, protects the fish from parasites, and makes the fish more mobile in the water.
Studies indicate that this slimy mucus reduces water drag by more than 2/3.
Next, I began observing the operculum. The operculum is a structure on the sides of the perch
face that help it to move oxygenated water across the gills. Acording to Dr. Wile, the process of oxygen
extraction is more than 80% effiecient in absobing oxygen from the water in just one pass through the
gills. They are a prominent feature in bony fish because they are often in motion in the live fish. I
counted the number of gills on each side. I found that there were {insert observation] gills on the left
side and [insert observation] gills on the right side.
Using scissors, I next cut the left operculum away and removed one set of gills. I placed the
gills into a bowl of water. I observed that there was a strong arch in each gill. This arch had a comb-like
structure (the raker) on one side and feathery extensions (the filaments) on the other.
[insert annotated photographs of the gill structures]
Internal Anatomy Observations:
Next, it was time to turn my attention to the perch internal anatomy. I held the specimen ventral
side up with the head pointing away from me. With the scalpel I made a cut from the anterior of the
anus all the way up to the operculum. Basically, a cut right up the belly. The next cuts create a flap by
cuting from the operculum up to a level just a bit higher that that of the eye and then up from the anus
up to about the same level as the anterior cut. The last cut will connect the top two points making a
'window'.
Moore, Timothy
[insert image of window cuts]
I removed the body wall and identified the visible internal organs.
[Insert annotated internal organ image here]
I carefully removed and observed the digestive organs previously identified. When the fish
feeds, , the food travels through the mouth and across the taste bud covered tongue. It then travels
through the muscular pharynx (throat0 and into the esophogus, which leads to the stomach. The
stomach was further dissected to see if the last meal could be identified.
[image of dissected perch stomach and other digestive organs]
The fish has two main organs that aid the intestine in digestion. The pyloric ceca secretes digetive
enzymes into the intestine and stomach. The liver, which is connected to the small intestine, secretes
bile. Bile is a mixture of salts and phospholipids that aid in the breakdown of fat. When food is not
flowing through the intestine, a valve shuts the liver off from the intestine, and the bile is concentrated
in the gall bladder.
Next, I focused on locating and identifying reproductive organs. Female ovaries are orange if
they contain eggs. If were a female that was not ready to lay eggs it would be beige and drumstick
shaped. For the male, the testes would be small and cream-colored. I had a [insert perch gender here].
[insert photo of reproductive organs]
Next, I focused my attention on the kidney. [insert observations of the kidney].
[insert image of the kidney here]
The air bladder is used by the perch to control buoyancy. Fish are denser than water. Without
Moore, Timothy
the air bladder, most of them would sink to the bottom. The fish, however, is able to direct gases from
its blood and digestive system to diffuse into the air bladder. If it wants to sink, it releases the gases
from the bladder. [insert observations of the air bladder]
[insert image of the air bladder here]
The perch has a two chamber heart, unlike an amphibian with three or a human which has a four
chamber heart. The upper one is the atrium and the lower one is the ventricle.
[insert image of the heart]
The system of arteries and veins, gave hints of the complex circulatory system in the perch. The
blood leaves the heart through a large blood vessel called the ventral aorta, which branches into a series
of smaller vessels called afferent brachial arteries. These supply blood to the gills, where the blood
releases carbon diaoxide and picks up oxygen. Now the blood leaves the gills through the efferent
barchial arteries which takes the blood into the dorsal aorta which bracnches to feed out into two
directions. One branch leads to the brain and head. The blood goes back to the heart via the anterior
cardial vein. If the blood takes the other path, it is sent to various organs and along the intestines to pick
up nutrients. The blood is directed to the kidney where the waste products that the blood has been
absorbing all along the way can be released and removed from the body. The blood is eventually
carried back to the heart via the posterior cardinal vein. Though the human circulatory system is more
complex than the perch, it is similar.
[insert vein and artery images]
I next turned my attention to the perch brain. I first cut the skin away from the skull. The skull
was carefully scraped to thin it until I could safely remove the skull without doing harm to the brain
underneath. I observed the structure and used the diagram provided in the text to identify the structures
that I saw. [summarize the differences that seem to be apparent between the human brain studied in this
module and the brain from the perch]
Moore, Timothy
[Insert annotated brain image here]
Conclusion
Observations unique to class Ostreichthyes were [insert summary].
Structures common to vertebrates that were observed were [insert summary].
References
[1] Wile, Jay and Marylyn F. Durnell. 2002. Exploring Creation with Biology, ed 1. 425, 426.
[2] Wile, Jay and Marylyn F. Durnell. 2002. Exploring Creation with Biology, ed 1. 425.
[2] Burman, William. 1984. How to Dissect: Exploring with Proble and Scalpel. 133