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Anatomy Dogfish Dissection PROCEDURES 2017 Objective: The Spiny Dogfish is a small, Do not write on this! cartilaginous fish that has long been a popular specimen for study in the Zoology. Its popularity is due to its large numbers and consequent ease of capture in the sea, convenient storage, and representative anatomy of primitive jawed fish. We are also able to use this in anatomy to discuss the differences in digestive systems of the shark and human. This is an extremely important lab grade. It is approximately 15 percent of your semester grade. You need to do a good job on this! Choose your partners wisely (you will need to work in groups of 4 or 5); if you have an unexcused absent during this time period it will count against you! The due date will be posted on line. I will ACCEPT ANY LATE WORK (only up to one week past the due date) on this assignment, but you will lose half credit. That means the best you can get is a 50 percent on your lab. Even if the lab is handed in the following morning. Procedures: 1) You will work in groups of four or five. This is due to the extreme expense of the specimens. You may discuss your definitions with your partners, but you may NOT COPY the definitions word for word. IF YOU COPY FROM A PARTNER; YOUR WHOLE GROUP WILL RECEIVE A 0. You will need to type up your definitions. You may want to split up the sections to make sure everyone is working and the lab is completed. The terms must be in your own words. I will also be grading you on participation. Your partners will also decide whether you deserve full credit or not. 2) Now it is time to receive a stinky, oily sharky to play with. You will also receive a garbage bag to store your shark. Do NOT throw this away at any point during the lab. You will need this bag for the entire dissection. I do NOT have any extras. 3) The first thing we will do is to compare the anatomical structure of the shark and the human. Place your specimen on a dissecting tray and examine its external features (USE THE HANDOUTS TO FIND THE NAME AND FUNCTION OF THE STRUCTURES). Note that its shape is streamlined, enabling it to glide easily through the water with the least possible resistance. The body is divided into three anatomical regions: the head, which extends from the tip of the snout to the pectoral fins; the trunk, which continues to the origin of the tail; and the tail, which is at the posterior end. 4) Draw, label and tell me the function of the following features: Caudal Dorsal Fin, Cranial Dorsal Fin, Caudal Fin, Dorsal Spine, Endolymphatic Pore, Placoid Scales, External Gill Slits, Eye, Eye Lid, Interbranchial Septum, Lateral Line System, Mouth, Naris, Pectoral Fin, Pelvic Fin, Spiracle, Claspers (on males only) and Spiracular Valve. Answer the questions on sharks on your observation sheet. Make sure these are in your own words and don’t copy from your partner. Remember to answer the question in the observation section in your own words. 5) You will be taking measurements of your shark before you cut the shark. What parts you need to measure are located in the table on your observation sheet; most of you will not have a dorsal spin (if it is not present simply record NA in the box). When I ask you to measure the caudal and dorsal lobe, that is referring to sections of the caudal fin. Make sure all measurements are in centimeters. The actual measurements are recorded on your observation sheet. Reproductive structure 5. Next you will determine the sex of your dogfish (Record this on your observation sheet). Do this by flipping your shark so its ventral side is facing up, and now look between the pelvic fins. Use the diagrams in the shark packet “External Anatomy” to help identify the sex of your shark. You only draw, label and define the sex of shark you are dissecting. You will need to draw, label and give me the function of the following parts: Male: anus, clasper, cloacal aperture, pelvic fin, and urogenital papilla. Female: anus, cloacal aperture, pelvic fin, and urinary papilla. Yes, some of these anatomical parts are repeated from your external anatomy section. Label them, but you do NOT have to define them twice. Muscular structure (CUT #1) 6. Follow the procedure below to skin your shark. You will draw the muscles that you see. You will need to label and give me the function of the following muscles: craniomaxillaris, preorbitalis, epihyoideus, coracohyoideus, branchial muscles, hypobranchial muscles, ventral longitudinal bundle, lateral longitudinal bundle, dorsal longitudinal bundle, intermandibulari, levator palaoquadrati, levator hyoideus, cucullaris, and dorsal constrictors. ONLY SKIN YOUR SHARK ON ONE SIDE!!!! To view them, remove a strip of skin from one side of the dogfish. You will begin on the dorsal midline cutting caudally from the Caudal Dorsal fin toward the Caudal Fin. This may be done by making a shallow incision. You will gently peel away the skin; be careful to not rip off the muscle (the skin is only 1/16 of an inch thick). Remove the skin all the way to the ventral midline of the shark. You will have removed all of the skin from the top of the shark towards the bottom and all the way back towards the tail. BE CAREFUL NOT TO PUNCTURE INTO THE INTERIOR OF THE SHARK! Explain to me how a shark (or any fish) for that matters moves. This is done in the conclusion section. INTERNAL ANATOMY (CUT #2) WARNING: BONES AND TEETH ARE VERY SHARP. BE CAREFUL BECAUSE IT IS EASY TO CUT YOURSELF. 7. In order to expose the coelom (internal body cavity), the body wall must first be dissected. To do this, follow the procedure below(use the place mat as a guideline, blue dotted line): - Place your specimen on a tray on its back to expose the ventral side. Using sharp scissors make a shallow incision through the skin layer from a point immediately cranial to the cloaca. Now cut cranially to the pectoral girdle slightly to the left of the midventral line (use Fig. 4.1 in your “Internal Anatomy” handout as a reference). It is important to avoid cutting along the midline near the pectoral girdle in order to prevent damage to underlying structures. Now cut through the muscle layer by making a deeper incision along the same path as the first incision through the skin. - Carefully extend the incision made above from the coracoid bar of the pectoral girdle to the level of the second gill slit. Cut through the body wall, but do not cut deeply. - Make a transverse incision through the body wall about midway between the pectoral girdle and the pelvic girdle. Extend the cut on both sides to the lateral line. - This WILL BE MESSY because of the oils found in the shark’s liver. Do not remove the flaps of skin so you can store your shark. When you are done with this cut, you may want to wrap the shark with paper towels. 8. Draw, label and define the following: Cloaca, Duodenum, Gall bladder, Heart, Liver, Pancreas, Pericardial Cavity, Spleen, Stomach, Transverse Septum, Uterus (only in females), anterior intestinal vein, anterior intestinal artery and Valvular Intestine. If any of these terms are repeated you will not need to define them twice. ORAL CAVITY: (CUT #3) The mouth or oral cavity is the space between the external ridge of the teeth and the internal opening of the spiracles. To view the oral cavity, follow the procedures below: -Begin the incision by cutting through the left corner of the mouth. BE CAREFUL YOU WILL BE VERY NEAR THE EXTREMELY SHARP NASTY TEETH OF AN OVERLY AGGRESSIVE SHARK!!! IT HAS MUSCULAR REFLEXES, WHICH MAY CAUSE THE JAW TO SHUT UNEXPECTEDLY!!! 9. (USE SCISSORS NOT A SCALPEL) Continue this cut through the Meckel’s cartilage, cartilages of the branchial arches and the hyoid arch. Look at figures 5.1(In the Digestive and Respiratory Handout) for a reference. Draw what you see on the observation page. You will need to label the following features and give their functions: tongue, teeth, , esophagus, Meckel’s cartilage, gill raker, gill filaments, interbranchial septum, branchial vessels, papillae, coelom and the pharynx. 10. Examine the digestive tract of the shark. Most of the structures you have already seen, but I would like you to draw and label only the digestive tract. Use figure 5.5 as a reference. It is on the last page of the “Digestive and Respiratory Systems”. Explain to me how the digestive system of a shark works (5 to 8 sentences answered in your conclusion section. Also, explain to me how a dogfish feeds, what it feeds on and how it replaces teeth. You will have to google the second part of this section. You may cut into the stomach and intestines to see if the shark has eaten anything. 11. You will now view the internal structure of the heart. The heart must be removed in order for it to be viewed. Cut the attachments of the sinus venosus to the transverse to the transverse septum. Now cut through the ventral aorta near its union of the fourth and fifth artery. Once the heart is removed you will draw a picture of the interior of the heart. You will need to label all the parts, but you only need to tell me the function of the following: atrium, ventricle, atrioventricular valve and the conus arteriosus. Explain to me how a shark circulatory works in five to eight sentences. There is room to do this on your dissection sheet. 12. Now you will look at the brain from the dorsal aspect. Remove the skin and other tissues from the dorsal surface of the head and around the eye. Carefully cut away the dorsal portion of the chondrocranium to expose the cranial cavity. You do not need bone cutters, scissors and scalpel should be fine. Continue to expose the brain by removing the supraorbital crest. Draw and label what you see. Give me the function of the following parts of the brain: Cerebral hemisphere, olfactory bulb, optic nerve, hypophysis, epiphysis, telencephalon, prosencephalon, mesenscephalon, rhombencephalon, myelecencephaln, metencephaln, tectum, medulla oblongata, and diencephalon. Some regions and functions will overlap, this section can get tricky I can help you with it. I would like for you to describe the senses of a shark; how it finds it food and detects it surroundings. 13. Finish your dissection by examining the ear of the shark. First locate the two endolymphatic ducts near the dorsal midline between the spiracles. Scrape the skin away from this region. Next slice the cartilage away in the thing sections until you can see the inner ear through its transparency. Label and give me the function of the following: utriculus, anterior semicircular duct, crista, ampulla, external spiracular pore, sacculus, horizontal semicircular duct, and posterior semicircular duct. 14. Make sure everything is clean, tray as well as your dissection kit.