Oceans 11 –Gaspereau Fish Dissection

Introduction:In this lab each student will work with a lab group in order to learn from the dissection of a fish. Before beginning the lab each student must read the background information and read through the procedures. Pictures and diagrams will aid in the completion of this lab dissection. Be thorough and do not rush through the lab. Read all directions carefully and make all drawings as accurate and neat as possible.

Background:

Gaspereau are members of the class Osteichthyes, or “bony fishes”. Thealewife(Alosa pseudoharengus) is a species ofherring. It is one of the "typical" North Americanshads.Alewife populations have exhibited drastic declines throughout much of theirrange. There are several threats that have most likely contributed to their decline, such as loss ofhabitatdue to decreased access to spawning areas from the construction of dams and other impediments to migration; habitat degradation; fishing; and increased predation.

Gaspereau spawn from mid-April to early May by depositing their eggs over vegetation or the water bottom, with no care given. The eggs are laid in large gelatinous adhesive masses. They usually swim up the Gaspereau river in schools, often numbering in the hundreds, and are often caught by using weirs or dip nets.The Gaspereau also has a streamlined body shape that makes it well adapted for movement in the water. Gaspereau have powerful jaws and strong teeth for catching and eating prey. They are primarily bottom feeders with a slow deliberate bite. They eat almost anything, but prefer minnows, insect larvae, plankton, and worms.

Physiology:

Food enters the fish's mouth and passes through the stomach and into the intestine. Digestion is aided by bile produced by the liver, which is attached to the intestine. Solid waste passes out through the anus.

Wastes from metabolism are processed by kidneys and pass out through the urogential opening. Oxygen is obtained from the water as it passes over the gills. The protective plate on each side of a fish's head that protects the gillsis the operculum. Waste carbon dioxide is passed into the water at the same time.

Movement is achieved by the action of muscles attached to the bony skeleton of the fish and is guided by the action of several types of fins(dorsal, caudal, pelvic, anal, and pectoral… which serve functions of protecting against rolling,propulsion, helping with sudden turns & stops, stabilization, and serving as “paddles” for changing direction). The fish uses an air bladder in its body to help itself stay afloat. The amount of gas in the bladder is adjusted by gas exchange across the capillaries in the air bladder wall. The lateral line, found on the outside of the body, allows the fish to sense differences in pressure and to sense low frequency sounds.

Materials:

  • Gaspereaufish (preferably fresh )
  • hand lens
  • dissecting tray
  • dissecting probe and scissors
  • pre-lab pictures & diagrams

The Dissection of a Fish – Oceans 11

Name: ______(partners) ______

External Anatomy:

1. Place the fishon a dissecting tray. Locate the head region. Examine the eyes.Are there any eyelids present? ______.Draw the eye in the space below. Label the eye on the external view (figure 1) of the fish.

2. Examine the two flaps located on either side of the head.

(A) What is the name of these flaps? ______
(B) What is their function? ______

(C) Label the flaps on the external view (figure 1) of the fish.

3. Examine the 5 types of fins. In each box below, draw one of the fish's five types of fins.

Dorsal
/ Caudal
/ Anal
Pelvic
/ Pectoral

4. Label each fin on the external view (figure 1)of the fish.
(A) How many fins? Caudal ____ Dorsal _____ Anal _____ Pelvic _____ Pectoral _____
(B) Summarize the function of these fins:

caudal fin______

anal fin______

dorsal fin______

pelvic fin______

pectoral fin ______

5. Locate the lateral line. Using the hand lens and look at the line and the surrounding area.

Label the lateral line on the external view (figure 1) of the fish.

B. Internal Anatomy: Gill

Using your thumb, lift up the edge of the operculum and raise it up as far as you can. Using your scissors, cut the operculum off as close to the eye as possible. You have exposed the gills. The gillsare layered one on top of another. Using your probe, carefully lift each of these layers.

1. How many layers do you find? ______Using your scissors, remove one of these layers. Examine the feathery structure.Draw the gill structure below.

To expose the internal organs you will cut away part of its muscular wall. Grasp your fish, holding it with your thumb on one side and fingers on the other. Turn your hand upward to expose the ventralsurface. Using your scissors, insert the point into the skin just in front of the anus. Cut forward to the gills. Be careful not to destroy any of the internal organs, since they are mostly found in this area.
Place your thumb into the open cut area and lift up, separating the bottom from the top. Using your scissors, cut upward near the anus and the operculum,so it forms a flap of skin and muscle. Finish cutting along the lateral line and remove the flap of tissue.

2. The fish contains a 2 chambered heart. Locate this organ found just behind and below the gills. Label the two main parts of the heart below.

(A)Part 1 ______Function: ______

(B)Part 2 ______Function: ______

(C)Label the heart on figure 3.

3. Locate the tube-like digestive system. Begin just behind the mouth in the area called the pharynx. This area leads into the gullet or the opening of the esophagus. This area is very elastic and can stretchwhen the fish is alive.

(A) How could this help the fish? ______
(B) Label the mouth, the pharynx, and the esophagus on figure 3.
(C) The esophagus leads to the stomach - Label the stomach on figure 3.

4. Locate the liver located just in front of the stomach. Label the liveron figure 3.

5. Followthe intestine to the anus.Label the intestine and anus on figure 3.

6. Locate the kidneys, found just below the spinal column. Their main function is to rid the body of nitrogenous waste. Label the kidneys on figure 3.

7. The swim bladder is the last remaining organ to be identified. It is located between the kidneys and gonads.Label the swim bladder on figure 3.

(A)What is the function of the swim bladder? Describe.