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Aquaculture Sample LessonAC104 Functional Anatomy of Fish 
MAIN IDEA: What are the main external and internal anatomical features of fish? An understanding of the anatomy of fish, both the internal and external structures, is essential for success in aquaculture. Anatomy aids in classifying and recognizing types of fish, distinguishing between the sexes, and in spotting and diagnosing disease. EXTERNAL ANATOMY Morphology or structure and form of fish can affect feeding and type of culture facility. For example, fish with small, upturned mouths generally are herbivores (plant-eating) and/or surface feeders like tilapia. Fish with downturned mouths are generally bottom feeders like catfish. Single-lobed or homocercal tail fins suggest that fish are slow swimmers and survive well in water free of much movement. Fish with forked or heterocercal tail fins are fast swimmers and prefer flowing water. The body shape of fish also suggests the type of culture facility to use. Fish like trout, with a body long and tapered towards the ends, are the best swimmers and need water space. Fish that are wide and flat or tend to stay on the bottom require lots of bottom space for growth. Fish that are rounded and thin from side-to-side or laterally compressed tend to hover in the water and are not particularly fast swimmers. Body Regions: Body regions of a fish include: 1) the head which runs from the tip of snout to the posterior edge of the operculum (the covering over the gills); 2) the trunk (from the operculum to the anus); and 3) the tail (from the anus to the end of the caudal fin). Fins: Fins on a fish include the single dorsal fins, the anal fin and the caudal (tail) fin; and the paired pectoral and pelvic (ventral) fins. Other Structures: Other important external structures include teeth in some fish, the nostrils or nares, the eyes, the mouth, the operculum, scales, the lateral line, the anus and the urogenital opening between the anus and the anal fin. Scales: Many fish are covered with bony or horny shaped plates called scales. These occur on the sides of the fish in overlapping rows. Some fish like catfish do not have scales. Surfaces: Any discussion of the structure and function of fish must entail an understanding of surfaces: dorsal, ventral, anterior and posterior.
These surface names can be used to describe the location of external structures, locate sites for injections and describe the movement of fluids. PHYSIOLOGY AND ANATOMY Physiology, or the function of fish, occurs in nine body systems adapted to the water environment. These systems include:
Skeletal System: The skeletal system is the rigid framework giving the body shape and protecting the organs. It is composed of bony or hard material and cartilage. Tissues and organs attach to the skeleton. Fish possess an internal skeleton, also called an endoskeleton. The head is composed of about 40 bones. The skeleton surrounding the body organs forms a compact movable support for the gill mechanism. Pectoral fins join the pectoral girdle that attaches dorsally behind the head. The pelvic fins move on two flat bony plates lying in the ventral trunk muscles. The vertebrae are more delicate, proportionately, than those in most land vertebrates. The vertebral column ends in several stout flat bones supporting rays of the caudal fin. The dorsal and anal fin rays articulate on intramuscular bones that alternate with the long dorsal and ventral spines of the vertebrae. Paired slender rib bones attach to each trunk vertebra. Muscular System: The muscular system provides movement internally and externally. Muscles vary in strength and function. Muscles contract and relax to cause movement. Fish require movement for such functions as obtaining food and oxygen and for eliminating wastes. Muscles on the sides between the anal and caudal fins are divided into muscle segments in what looks like a sideways shaped "W" extending from mid-dorsal to a mid-ventral line. Each segment is separated from those adjacent by connective-tissue partitions. A lengthwise partition beneath the lateral line separates each segment into dorsal and ventral parts. Digestive System: The digestive system converts feed into a form that can be used by the body for maintenance, growth and reproduction. It consists of all of the parts of an organism involved in taking food into the body and preparing it for assimilation, incorporation into the body. Digestive systems vary according to whether the animals are herbivores eating only plants, carnivores eating only animals, or omnivores eating plants and animals. In fish, the digestive system includes the mouth, esophagus, stomach, intestines, anus and other associated organs like the liver and gall bladder. Also, many fish have slender, blind pouches attached to the anterior portion of the intestine where the stomach and intestine meet. These are called pyloric ceca. Enzymes secreted in the pyloric ceca and intestine break down the food for absorption by the fish. Excretory System: Life processes produce waste products. The excretory system eliminates wastes from the body. In fish the excretory system consists of the kidneys, urinary ducts, urinary bladder and urinary opening. Kidneys filter the wastes from the blood. The urinary bladder holds the wastes until they are excreted through the urinary opening. Respiratory System: The respiratory system takes in oxygen from the water and delivers it to the tissues and cells of the body. The respiratory system also picks up carbon dioxide from the tissues and cells, delivering that carbon dioxide back to the water. Gills are the respiratory organs of fish. Water taken in is forced over the gills where oxygen is removed by diffusion into the blood. Gills are in a common cavity at either side of the pharynx (just behind the mouth). Gills are covered by a structure called the operculum. They are arranged in double rows of gill filaments, and a bony arch supports each gill. Gill rakers on the inner surface of each arch protect the delicate gills from food passing through the pharynx. Circulatory System: The circulatory system distributes blood throughout the body. In fish this system consists of a heart, veins and arteries. Pumping action of the heart causes blood to flow through the arteries to the gills where the blood picks up oxygen and carries it to the rest of the body. Oxygen is necessary for all cells of the body. As the blood delivers oxygen to the cells of the body, it picks up carbon dioxide which is carried in the blood back through the veins to the heart and gills. The gills release the carbon dioxide back into the environment and pick up more oxygen. The blood also carries nutrients and waste products. In fish, the heart is located in the pericardial sac, beneath the gill region. Nervous System: The nervous system supplies the body with information about its internal and external environment. This system conveys sensation impulses -- electrical-chemical changes -- between the brain or spinal cord and other parts of the body. The nervous system consists of the brain, spinal cord, many nerve fibers and sensory receptors. It is a complex system. The sense organs or receptors receive stimuli and convey these by the nerve fibers to the brain or spinal cord where they are interpreted. The brain or spinal cord may send responses to the stimuli back through the nerve fibers. Sensory System: The sensory system includes the five senses -- sight, touch, taste, smell and sound. The sensory system relays information through the nervous system. Fish use eyes to find food and identify predators. Ear bones in the skull pick up water vibrations as sound. Some species have an enhanced sense of touch through organs like the barbels around the mouth of catfish. Lateral lines on the external surface of fish contain nerves that detect water vibrations and motion. Reproductive System: Sexual reproduction is the process of creating new organisms of the same species through the union of the male and female sex cells -- sperm and eggs. Testes in the males produce sperm. Ovaries in the females produce eggs or ova. Fertilization occurs when the sperm unites with the egg to form a zygote. After a period of incubation, the zygote develops into a new organism. Sperm and eggs in fish are discharged through ducts to the urogenital opening at the time of mating. SWIM BLADDER The swim bladder is a long, thin-walled sac, located dorsal in the body cavity (near the backbone) and attached to the pharynx. This organ controls the buoyancy of a fish, and in some species it is important for hearing. Not all fish have a swim bladder. EXERCISES:
1. Use Internet or other resources to label a diagram or make a labeled diagram of all the external features of a "typical" fish including the following: 2. Use Internet or other resources to draw and label a diagram of a "typical" digestive tract of a fish including the following: A. Esophagus B. Stomach C. Liver D. Pyloric ceca E. Intestine 3. Develop a report or presentation on the function of the lateral line or the swim bladder. 4. Practice identifying and using the terms dorsal, ventral, anterior and posterior on humans, pigs, dogs and horses. INTERNET RESOURCES:
** Australian Museum Fish site - Dissection
** Florida Fish and Wildlife Conservation Commission - Fish Anatomy
** Hubbard's Fish Anatomy
** Nebraska Scientific
** Ohio State University - Fish and Their Diseases - Anatomy and Physiology
** Sea World - Anatomy and Physiology
** Texas Parks and Wildlife - Fishes Found in Texas Fresh Waters
** USDA Forest Service - Fish and Life Cycles
** Virginia Cooperative Extension - 4-H Virtual Farm - Fish Anatomy TEST: 1. The shape of a fish tail suggests whether they are fast or slow swimmers. TRUE or FALSE?
2. Name the three body regions of the fish. 3. Identify the paired fins.
4. List the names that describe the four surfaces of a fish. 5. Fish possess an internal skeleton or __________ . 6. Where are the pyloric ceca found? 7. __________ are the respiratory organs of fish. 8. Lateral lines are a part of the circulatory system. TRUE or FALSE? 9. At the time of mating, sperm from the male and eggs from the female are discharged through ducts to the __________ opening. 10. Urinary bladders in fish control the buoyancy of the fish in water. TRUE or FALSE?
----------------------------------------------------------------------------- END STUDENT SECTION AC104 Functional Anatomy of Fish TEACHER'S GUIDEOBJECTIVE: Students will recognize the important external and internal structures of fish.
PREPARATION: Take the following steps to prepare for this lesson: REFERENCE: Parker, Rick. "Aquaculture Science." Clifton Park, New York: Delmar Publishers, 2002. INTERNET RESOURCES:
** Australian Museum Fish site - Dissection
** Florida Fish and Wildlife Conservation Commission - Freshwater Fish Anatomy
** Hubbard's Fish Anatomy
** Nebraska Scientific
** Ohio State University - Fish and Their Diseases - Anatomy and Physiology
** Sea World - Anatomy and Physiology
** Texas Parks and Wildlife - Fishes Found in Texas Fresh Waters
** USDA Forest Service - Fish and Life Cycles
** Virginia Cooperative Extension - 4-H Virtual Farm - Fish Anatomy IMPORTANT TERMS: morphology, homocercal, heterocercal, operculum, trunk, caudal, dorsal, pectoral, pelvic, nares, urogenital, anterior, posterior, caudal, endoskeleton, lateral line, pyloric ceca, urinary, diffusion, gill rakers, gill filaments, pharynx, pericardial sac, barbels, urogenital, swim bladder. EXTENSION IDEAS: 1. Obtain fresh or preserved samples of fish for students to dissect. Preserved fish can be obtained from Nebraska Scientific, listed under Internet Resources below. Have students identify all of the major external and internal structures. Also have them examine the muscles of the fish. If actual dissections are not possible, several companies sell computer programs that lead students through a virtual dissection. Information about Insight-clopedia Fish is listed under Internet Resources. Another possibility is the dissection shown at the Australian Museum Fish site listed under Internet Resources. 2. Examine fish scales under low magnification on a compound microscope. 3. Develop a bulletin board presentation showing some of the differences in the external features of fish. For example, you might show the differences in tails, dorsal fins, scales, mouth, barbels and body shape. 4. Visit an aquarium so student can observe the different external features of live fish and their habitat, or maintain an aquarium in the classroom with some different species of freshwater fish. EXERCISE ANSWERS: 1. Students can find many Internet sites and books that describe the external features of fish. Perhaps the most difficult will be the labels on the fins, since some variations occur. 2. Fish have a very short esophagus leading to a small stomach. The pyloric ceca are located on the intestine next to the stomach. Then the intestine coils some and continues on to the anus. 3. Lateral lines on the sides of fish represent sense organs or receptors that receive stimuli and convey these by the nerve fibers to the brain or spinal cord where they are interpreted. The brain or spinal cord may send responses to the stimuli back through the nerve fibers. Lateral lines detect water vibrations and motion. The swim bladder controls the buoyancy of a fish. Neutral buoyancy, the ability of a fish to use little or no energy to stay at a particular level of water, is achieved through the expanding and shrinking of the swim bladder due to varying gas pressures. Without a swim bladder, fish would sink. 4. Any anatomy book will identify these surfaces in the various species. TEST KEY: 1. The shape of a fish tail suggests whether they are fast or slow swimmers. TRUE or FALSE? TRUE.
2. Name the three body regions of the fish. 3. Identify the paired fins. Pectoral and pelvic (ventral) fins
4. List the names that describe the four surfaces of a fish. 5. Fish possess an internal skeleton or endoskeleton. 6. Where are the pyloric ceca found? In the anterior portion of the intestine 7. Gills are the respiratory organs of fish. 8. Lateral lines are a part of the circulatory system. TRUE or FALSE? FALSE. Lateral lines are part of the sensory system. 9. At the time of mating, sperm from the male and eggs from the female are discharged through ducts to the urogenital opening. 10. Urinary bladders in fish control the buoyancy of the fish in water. TRUE or FALSE? FALSE. The swim bladders control the buoyancy of the fish in water. CROSSWORD PUZZLE ANSWERS:
Across: 2. Trunk, 5. Herbivore, 7. Nares, 8. Heterocercal, 9. Caudal, 11. Ventral, 12. Head, 13. Anterior. END TEACHER'S GUIDE
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