Perch Dissection Pre-Lab

Dissection Terms • Anterior: situated before or at the front of

• Posterior: situated behind or at the rear of

• Ventral: situated on or toward the lower, abdominal plane of the body; equivalent to the front, or anterior, in humans.

• Dorsal: situated on or toward the upper side of the body, equivalent to the back, or posterior, in humans.

• Caudal: of, at, or near the tail or the posterior end of the body.

External Perch Anatomy

Perch Classification in Domain Eukaryota

• Kingdom: Animalia

– Phylum: Chordata

• Subphylum: Vertebrata

– Infraphylum: Gnathostomata

» Superclass: Osteichthyes – bony fish

• Class: Actinopterygii

• Order: Perciformes

• Family: Percidae

• Genus: Perca

• Species: Perca flavescens

Internal Perch Anatomy

How do Gills work in respiration? • The gill works by providing a

surface where the water (which has dissolved oxygen) comes into contact with the blood of the fish.

• The blood circulation within the

gill is arranged in such a way that it flows in opposite direction to the flow of water (=countercurrent arrangement).

• Because oxygen will tend to flow

(diffuse) from the site of highest concentration to the place of lowest concentration, this arrangement ensures that oxygen will always flow from the water into the blood.

Oxygen is not as abundant in water as it is in the air, so for aquatic animals, oxygen concentration is a major limiting factor.

The best way to ensure that enough water is "scanned" for oxygen at the gills is providing a really large surface area for gas exchange.

Thus, each gill is formed by filaments. Each filament has secondary lamellae that rise perpendicularly to the surface of the filament. The total surface area is extremely large with respect to the volume of the gills.

Gas exchange occurs at the secondary lamellae, and it's here where you can see the countercurrent circulation.

How does the swim bladder help keep the fish buoyant?

• When gas is added to the swim bladder, the fish becomes less dense.

• When gas is removed from the swim bladder, the fish becomes more dense.

• A swim bladder is filled

with air when the fish wants to ascend, and it is deflated when the fish wants to descend.

Dissection • Remove operculum with scissors

– Observe gill anatomy

• Rakers - white, comb-like arches

• Filaments - Red fingerlike projections

• With a scalpel, remove a section of the lateral line

– What function does this organ serve?

– Do you notice a concentration of nerve endings?

• Begin the main incision

– Open the abdomen (below the gill) carefully with a scalpel

– Cut with a scissors: remove a oval-shaped piece of skin (only skin) running from underneath the gills, to the anus, up to the lateral line, along the lateral line, to the gill, down to where you started the incision. Remove flap of skin (see diagram on next slide)

Main Incision

Cut along the blue line...

• Only cut through scales, muscles, and skin

• Take special care not to cut too deep!

Anterior View

1. Gills

2. Heart

3. Liver

4. Pyloric caeca

5. Small intestine

6. Stomach

7. Swim bladder

Posterior View

1. Swim bladder

2. Gonad

3. Large intestine

4. Urinary bladder

5. Anus

Close-up: Body Cavity

Muscle

Swim

Bladder

Liver

Spleen

Gastric

Cecae

Eggs

Stomach

Ovary

Small

Intestine

Can you identify the parts?