Tilapia Dissection and Guide PDF

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Name: MANALO, NHEANNE GEENE B. Course, Year & Section: BS Biology 1 (B)

Score: ____________________ Date: 12/14/2021

TILAPIA DISSECTION The Nile tilapia (Oreochromis niloticus) is an African cichlid native to Burkina Faso, Cameroon, Chad, Cote d’Ivoire, Egypt, Gambia, Ghana, Guinea, Liberia, Mali, Niger, Nigeria, Senegal, Sierra Leone, Sudan, Togo and Uganda. Nile tilapia is an important food fish that has been introduced to many different parts of the world by man and through aquaponics. It can today be found on all continents except Antarctica. In several countries, Nile tilapia has become a problematic invasive species after its introduction.

Nile tilapia inhabits a lot of different waters, from lakes and rivers to irrigation channels and sewage canals. It is considered a freshwater species but will tolerate brackish conditions as well. In the wild, it is typically found in waters where the temperature stays in the 13.5-33 °C (56-91 °F) range. The extended temperature range for this species is however 8-42 °C (47-108 °F). Nile tilapia is principally a day active fish that feeds chiefly on phytoplankton and benthic algae. It can also eat plants and have been introduced to ponds to reduce the amount of aquatic weed. Just like many other African cichlids, the Nile tilapia is a mouthbrooding species where the female fish will keep egg, larvae and fry protected inside her mouth until the fry is large enough to be released.

Lab Questions #1: 1. Tilapia belong to what class of bony fish?  Class Osteichthyes, Subclass Actinopterygii 2. Are Tilapia ray-finned or lobe-finned fish? Explain.  They are ray-finned fish because they have a rigid skeleton. 3. Name the fins found on the Tilapia. What function(s) do the fins serve?  Aside from the tail or caudal fin, fish fins have no direct connection with the spine and are supported only by muscles. Their principal function is to help the fish swim. Fins located in different places such as the pelvic fin, anal fin, and dorsal fin serve different purposes such as moving forward, turning, keeping an upright position or stopping. 4. Give the function for the swim bladder.  The swim bladder is a gas-filled organ in the dorsal coelomic cavity of fish. Its primary function is maintaining buoyancy, but it is also involved in respiration, sound production, and possibly perception of pressure fluctuations. 5. Describe the external appearance of the Tilapia.  The external features of the tilapia includes the scales, slimy, dorsal fins, pelvic fins, anal fin, and the caudal fin. It also has the head and the lateral line. 6. What is the scientific name for this species of fish?  Oreochromis niloticus 7. Describe spawning of Tilapia.  The ripe female spawns in the nest, and immediately after fertilization by the male, collects the eggs into her mouth and moves off. The female incubates the eggs in her mouth and broods the fry after hatching until the yolk sac is absorbed. 8. Name several organs that belong to the digestive system of the Tilapia.  Mouth, esophagus, stomach, intestine, anus 9. Describe the heart of a Tilapia and explain blood flow through this region.  The heart is located a little behind and below the gills. The typical fish heart has four chambers, however unlike mammals, blood moves through all four in sequence. Venous blood enters the sinus venous (a thin walled sac) then flows into the atrium, followed by the ventricle (a thick walled pump). 10. Where the lateral line found and what is is its job?  The lateral line is a sensory system that allows fishes to detect weak water motions and pressure gradients. Materials List:

       

Tilapia Dissecting pan Scalpel Scissors Forceps Gloves Eye cover Ruler/string

Procedure: External Anatomy 1. Place the fish in your dissecting pan. 2. Label the anterior, posterior, dorsal and ventral sides of the fish. 3. Measure the length and the girth of the fish, including fork length.

Table 1: Fish Measurement (inches) Total Length Fork Length Girth

8. 4 inches 7. 9 inches 5.6 inches

5. Locate the 3 body regions of the Tilapia- head, trunk, and tail. Label these on figure 1. 6. Open the mouth and observe its bony jaws. Locate and label the upper jaw or maxilla and the lower jaw or mandible. 7. Fell the inside of the mouth for teeth. Locate and label the tongue and teeth on figure 1. 8. Open the mouth wider and use a probe to reach back to the gill chamber. 9. Locate the nostrils and label on figure 1. 10. Locate and note the location of the eyes. Label on figure 1. 11. Find the bony covering on each side of the fish’s head called the operculum. The opercula cover and protect the gills. Label on figure 1. Figure 1- External Tilapia Anatomy Soft Dorsal Fin

Spiny Dorsal Fin

Caudal Fin

Nares Operculum Eye

Peduncle

Mouth Pectoral fins Pelvic fins

Vent

Lateral line

Scales Anal Fin

12. Use a probe to lift the operculum and observe the gills. Note their color.

13. Use scissors to cut away one operculum to view the gills. Find the gill slits or spaces between the gills. 14. Use your scalpel to carefully cut out one gill. Find the cartilage support called the gill arch and soft gill filaments that make up each gill. Label the parts of the gill in Figure 2. Figure 2- Gill Structure

15. Observe the different fins on the Tilapia. Locate the pectoral, dorsal, pelvic, anal, and caudal fins. Note whether the fin has spines. Label these on Figure 1 and complete table 2 on fins. Table 2- Fins Name of Fin Caudal Fin

Spines (yes or no) No

Number of Fins 1

Pectoral Fin

Yes

2

Anal Fin

Yes

1

Pelvic fin

Yes

2

Dorsal fin

Yes

2

Location Tail

Function

Provides the power to move a fish forward. It also acts like a rudder to help a fish steer. Near the Do everything that pelvic operculum fins do, and also help steer and control depth. Near the anal Provides stability, (below functioning like a keel on the bottom of a boat. Below the help balance the fish, keep pectoral fins it level, and prevent it from rolling from side to side Above the increase the lateral surface fish of the body during

swimming, and thereby provide stability but at the expense of increasing drag

15. Locate the anus on the perch anterior to the anal fin. In the female, the anus is in front of the genital pore, and the urinary pore is located behind the genital pore. The male has only one pore (urogenital pore) behind the anus. Determine the sex of your Tilapia. 16. Find the lateral line on the side of your perch. Label this line on Figure 1. 17. Use forceps to remove a few scales from your fish. Observe the scales under the magnifying glass. Sketch a scale on Figure 3. Figure 3 - Structure of a Scale

18. Count the growth rings on your scale to tell the age of your fish. (Hint: each ring represents one year's growth.) *Can’t determine clearly but I believed it is lesser than a year old since I only saw one growth ring but the fish doesn’t like a year old fish. Procedure (Internal Anatomy): 1. Use dissecting pins to secure the fish to the dissecting pan. Use scissors to make the cuts through skin and muscle shown in Figure 4. Figure 4 - Cut Lines for Internal dissection

2. After making the cuts, carefully lift off the flap of skin and muscle to expose the internal organs in the body cavity. 3. Locate the cream colored liver in the front of the body cavity. Also locate the gall bladder between the lobes of the liver. Label these on Figure 5. 4. Remove the gall bladder & liver to observe the short esophagus attached to the stomach. Label the stomach on Figure 5 5. At the posterior end of the stomach are the coiled intestines. Locate and then label these on Figure 5. 6. Find the small reddish brown spleen near the stomach and label this on Figure 5. 7. Below the operculum, are the bony gill rakers. Locate these & then label them on Figure 5. 8. In front of the liver & behind the gill rakers is the pericardial cavity containing the heart. The heart of a fish only has 2 chambers --- an atrium & and a ventricle. Locate the heart & label it on Figure 5. 9. In the upper part of the body below the lateral line is the swim bladder. This sac has a thin wall and gives the fish buoyancy. Label the swim bladder on Figure 5. 10. Below the swim bladder are the gonads, testes or ovaries. In a female, these may be filled with eggs. Label the gonads on Figure 5. 11. Find the 2 long, dark kidneys in the posterior end of the Tilapia. These filter wastes from the blood. Label the kidneys in Figure 5. 12. Wastes exit the body through the vent located on the ventral side of the Tilapia. Label this structure on figure 5.

Figure 5 - Internal Tilapia Anatomy

Swim Bladder Stomach

Gill rakers Liver Heart

Gonad

Kidney Vent

Spleen Intestines

Questions & Observations: 1. Are both jaws of the fish equally movable? Explain your answer. 

The upper jaw is fixed and will not move. The mandible is the moveable part of its jaw.

2. Does the Tilapia have eyelids? 

Fish don’t have eyelids.

3. How many gills are located on each side of the Tilapia? What covering protects them?  It has 4 pair of gills and the operculum covers it.

4. What is the function of the gill rakers?  Involved with suspension feeding tiny prey and stops clogging. 5. Explain how gas exchange occurs at the gills.  Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place and separates saltwater with pure oxygen. 6. Which fin was the largest? What other difference do you notice in this fin when it was compared to the others?  The largest fin is the dorsal fin. It has more jobs and stabilizer or balance the fish. 7. What was the sex of your fish?  Female 8. What is the function of the lateral line?  Allows the detection of movement, vibration, and pressure gradients in the water surrounding an animal, providing spatial awareness and the ability to navigate in the environment. 9. Describe how the scales are arranged on the trunk & tail of your fish.  The scales are arranged facing the tail. 10. Explain how the swim bladder controls buoyancy. 

When the swim bladder expands it will increase in volume and therefore displace more water. This increases the fish's buoyancy and it will float upward...