Introduction to Marine Biology – Fish dissection practical Name of student: Date:
Exercise #2: Fish Dissection PART A – Dissection of Osteichthyes
1. Open the abdominal cavity by cutting a window in the left side of your specimen. Use scissors to make a cut from the vent along the ventral midline until you cut through the pelvic girdle. Next, go back to the vent and cut dorsally until just before you reach the lateral line. Continue the cut anteriorly and just ventral of the lateral line until you reach the operculum.
NOTE: cut gently and slowly with the scissors to avoid damaging the external organs.
2. Cut the operculum off your specimen, exposing the gills and expose organs of the abdominal cavity as shown in Figure 3.1. Use cotton balls/ surgical towels to clean away the body fluids. 3. Cut away the body wall below the gills to expose the pericardium and heart. NOTE: be gentle with the heart, teleost fish have spongy cardiac ventral that can be punctured 4. Remove an entire gill, including the lamellae, gill arch and gill rakers from your specimen. Use forceps to scrape the mucus off.
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Introduction to Marine Biology – Fish dissection practical Name of student: Date:
Internal anatomy: G, gill lamellae; GA, gill ach; IN, intestine, PA, pancreas, RTS, right testis, S, stomach.
5. Determine the gender of your fish. If your fish has a single large organ that appears to be full of small spherical objects (eggs) and is ventral to the swim bladder in the posterior portion of the abdominal cavity, then your is if female. If it has two large cream coloured organs in the same general position as the ovary then your fish is male. 6. DRAW the anatomy of the abdominal cavity before removing the organs. 7. Remove the left testis or the ovary with a scalpel. Next, carefully cut away the liver and uncoil the intestine. This will allow you to more easily see and identify organs such as the spleen (deep, rich red coloured), kidney, pancreas and liver.
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Introduction to Marine Biology – Fish dissection practical Name of student: Date:
PART B – Cartilaginous fish (Chondrichthyes) e.g. dogfish / skate Sharks, skates and rays have modified form of the same basic body plan and are therefore included in the Elasmobranchii taxon. They are primarily demersal fishes. That is, they live on or near the sea floor where they feed mainly on benthic invertebrates. Their pectoral fins are greatly enlarged while the other fins are reduced in size. In this exercise you will examine at least one representative of non-shark members of the Chondrichthyes.
1. Make an incision along the ventral midline, starting at the cloaca and ending anterior of the pectoral fins. 2. Make lateral incision at the anterior and posterior ends of your longitudinal incision. Fold the body wall back, exposing the organs in the abdominal cavity. You may cut away the body wall if needed. 3. Rinse the body cavity and use paper towels to remove excess fluids. 4. DRAW the internal anatomy before removing the organs. Compare with your previous observations of Osteichythes.
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Introduction to Marine Biology – Fish dissection practical Name of student: Date:
The dashed lines on the ventral view show where you should make incisions to expose the abdominal cavity, heart and branchial region of the skate.
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Introduction to Marine Biology – Fish dissection practical Name of student: Date:
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