Transcript Trout Dissection

Oncorhynchus mykiss
Rainbow Trout Anatomy
A Study and Dissection Guide.
NOTES:
A. You will need a copy of the “Trout Book” with internal organs.
B. On your copy, circle the name of each underlined part that you find in the trout.
TroutDissection.dnr.sc.gov Adapted by Joyce Plyter 2013
1
Name_____________________
Date___________________
2
External Anatomy
Tail
Trunk
Head
The slim shape, and smooth scale covering of fish help them swim
through the water.
1. Examine the scales that cover and protect the fish. They grow as
the fish grows. Each growth spurt will show on the scales as a “ring” or
ridge. There will be several rings each year.
2. Use a microscope to view the growth rings of a scale.
3
Fins
Dorsal Fin
Adipose Fin
Caudal or Tail
Fin
Anal Fin
Pelvic Fins
Pectoral Fins
3. Find each fin. The adipose fin is often clipped in hatchery fish.
The pelvic fins help the fish move up and down.
The caudal fin or tail fin provides the “push” for the trout to start
moving and also acts as a rudder for steering.
The pectoral fins act as brakes and turn left and right.
Anal, adipose and dorsal (top) fins are used for swimming and balance.
4
Sense Organs
Eye
Scales
Lateral Line
Operculum
Mouth
The lateral line runs from the head of the fish to the tail. It detects
Dar
vibrations or waves in the water. This helps keep the trout from
bumping into things and helps sense danger.
The operculum is a hard plate that covers the delicate gills.
Trout use their mouths to grab food, bring in water and to feel things.
The pupil of the eye is slightly triangular in shape which helps the trout
see above, in front and below, but each eye only sees on its side.
5
Eye
Trout can see things both near and far away. The
large pupils let as much light as possible enter the
eye. The eye needs no lid, as it is always in water.
The eyes are placed so they work separately. Our
eyes work together, which give us depth
perception.
4. Make some “Trout Goggles”. Ask for the
pattern or place a “blinder” on your head between
your eyes to force each eye to work separately.
Try walking, writing and talking to someone.
Lens
The lens in
the eye
moves around
and allows
fish to focus
on objects.
6
Mouth
5. Open the mouth. Find and touch the teeth. Check the jaws, roof of the
mouth and even the tongue for teeth. Think about trying to get your finger
out if the trout clamped down. The teeth are for holding, not chewing.
Trout swallow their food whole.
Nostril or Nare
The nare is a
closed sac. It
helps the fish
to smell odors.
Teeth
Teeth are found
along the upper and
lower jaws. They
grasp and hold onto
prey.
Dar
7
Mouth
Food passes
through the
esophagus to
the stomach.
Gill rakers strain particles
out of the water to keep
the gills from getting
clogged and injured.
Dar
8
Gills
Operculum
6. Pull back the operculum to show the gills. Find 4 layers.
9
Gills
Gill filaments
Gill arch
Dar
Water is taken in through the mouth and passes over the gills.
The blood in the gills take oxygen (O2) from the water and
release carbon dioxide (CO2). Body cells need O2 to burn food.
10
Internal Anatomy: The Dissection
Dar
7. Read all of this page before you start. Using the line above for a
guide, use dissecting scissors to cut a flap of skin and muscle so you can
see the internal organs.
Start at the vent opening. Cut through skin and muscle, checking as you
go. You need to get into the body cavity, but not so deep as to cut
organs. Pull the flap down, but leave it attached.
Trout Book: A Paper Trout
Dar
8. Match the “Trout Book” “paper organs” with each actual organ of
your trout as you work. Color each paper organ to match the actual
organ.
9. As you find an organ, use a flap of tape at the top of the colored
paper organ to attach it to your “Trout Book”. Match the trout.
Using a flap of tape lets you lift each organ to see what is under it.
Internal Anatomy
Stomach
Pyloric caeca
Swim bladder
Dar
Heart
Liver
Gall bladder
Spleen
Kidney
A female has ovaries that produce eggs along the kidney. It may or may
not have eggs. A male will have a testes that produces male sperm cells.
13
Kidney
Kidney
Dar
The kidney filters waste from the blood stream and also makes
blood. Two canals carry waste from the kidneys to the bladder, an
almost clear storage bag.
From the bladder, the liquid waste passes to the outside through a
hole called the vent.
14
Swim Bladder
This is an inflated
swim bladder.
The swim bladder is like an
adjustable balloon or life
jacket. It allows the trout to
float and move up and down in
the water. To fill the swim
bladder, fish gulp and swallow
air. Fish “burp” to get air out
of the swim bladder.
Dar
10. If the swim bladder is
empty, use a clean straw to
fill the swim bladder with air.
You may need to remove it
from the fish.
15
Digestion
Dar
Stomachs:
Fat
Intestine
11. Use your straw to trace the pathway of food from the mouth
through the esophagus to the stomach.
16
Mouth
Path of Digestion
Cardiac stomach
Vent
Pyloric stomach
When a trout eats, both food and water enter the mouth.
Water is directed to the gills, and food goes to the esophagus which
leads to the stomach. Food moves through the stomachs into the
intestines as it is digested. Most of the digested food is picked up by
the blood (absorption) at the pyloric stomach (caeca). The intestine
does some digestion and absorption and then undigested substances
move out the vent (anus).
17
First or Cardiac Stomach
Dar
Dar
Digestion of food starts in the cardiac stomach or first stomach.
Food is swallowed whole. Acid and enzymes are added to digest
protein. Muscles squeeze and mix. If your trout just ate, there
may be food in the stomach. It is a carnivore, so eats other
animals.
12. Cut the stomach, starting at the lower end. Cut toward the
mouth and then look inside to see if and/or what it ate.
18
Second Stomach: Pyloric Caeca
The pyloric caeca
(see-ka) act like our
small intestine. They
release digestive juices
that break down food
to liquid. Liquid food
(nutrients) go into the
blood stream here
(absorption) and at the
intestine .
Our small intestine is
long and curled around
in our abdomen. The
long trip gives the food
time to digest and go to
our blood stream.
Pyloric caeca
19
Liver and Gall Bladder
Gall
Bladder
Dar
The liver filters the blood and produces bile which is stored in
the gall bladder. Bile breaks down (digests) fat.
The gall bladder is connected to the liver and stores bile made by
the liver. It is a thin storage bag and may be greenish in color.
20
Spleen
Dar
The spleen makes and stores blood cells.
21
Heart
Dar
Bulbus arteriosus
Atrium
Ventricle
22
The heart consists of two
chambers, the soft atrium that
receives the blood and the muscular
ventricle that pumps the blood to
the body.
Heart
The blood first passes through
bulbus arteriosus to the gills where
it picks up oxygen, then circulates
through the body to the organs
where nutrients, gases and wastes
are exchanged.
Valves keep the blood from going
backwards. A valve is a one-way
gate. When the ventricle squeezes
(pumps), the blood has to go toward
the gills because the “gate” to the
body (where the blood came into
the heart) is closed.
Dar
Atrium
Bulbus arteriosus
Ventricle
23
Brain
Cerebellum
To spinal cord
Optic lobes
The brain is the control center of the
fish. All sensory information is
processed by the brain. Automatic
functions (such as breathing) and higher
behaviors ("Should I eat that critter ?")
happen in the brain.
The olfactory lobes, for smell and taste,
are located inside the nostrils of the
fish and are connected to the brain by
olfactory nerves.
Dar
The large optic lobe is used for sight
and the cerebellum in the rear
coordinates and regulates muscle
activity. The spinal cord exits the rear
of the brain and passes through the
vertebrae, which gives it protection.
Signals from the lateral line go to the
brain along the spinal cord.
24
www.classroomaquarium.org.
25
Trout Anatomy Poster by Ed Huff
26