Dissection 101: Perch Reasons to Use the Dissection Video and Accompanying PowerPoint Presentation Reduce the number of specimens used by a class Increase the quality of the dissection for the students Review opportunity, increasing the learning experience for the students Student unable to dissect due to pregnancy or hypersensitivity to the preservatives Student chooses not to dissect due to ethical/moral reasons Click

Dissection 101: Perch Click Safety Considerations Age appropriate activity for the children in your care Material Safety Data Sheet (MSDS) available for accident reference Poison control number/phone readily available Latex free gloves, eye protection and apron/lab coat Eyewash station, shower and sink Sharp instruments (cut away from self and others) Sharps and specimen(s) disposal Encourage students to report all accidents Basic science laboratory rules (strictly enforced) As an educator you are responsible for the implementation of the dissection activity described in the video and PowerPoint. You must have safety procedures and rules established for your classroom and make sure all of the students follow the rules to ensure a safe environment. South Dakota Public Broadcasting and Dakota State University cannot in any way be responsible or liable for any injury as a result of performing the described dissection. Complete the dissection if you feel it is appropriate and safe for your individual class. Have fun and stay safe! Click

Perch Dissection 101: Click Perch are vertebrates in a group called the “ray finned fishes” because they have rays/spines in their fins. They are the largest group of vertebrates; there's more than 20,000 species of these, which is nearly three times the next largest group of vertebrates. Click

Dissection 101: Perch Click Perch (fish) characteristics: Fins – Provide movement forward (propulsion), maneuverability (directional movement), and stabilization Vertebrate – has backbone (spinal column) Uses gills for respiration Lives entire life in water Click

Exterior of the Perch Click Dorsal fin (cranial and caudal sections) - Stabilize Caudal fin - Movement forward Graphic: SD Game Fish & Parks Pectoral fins (paired) - maneuverability Anal fin - Stabilize Pelvic fins (paired) - maneuverability Click

Exterior of the Perch Preserved Yellow Perch Click Closeup: Anal fin Closeup: Caudal fin Closeup: Paired pectoral & pelvic fins Your specimen will look similar to the photo above, not the graphic on the preceding page. (notice the rays/spines) Closeup: Dorsal fin Click

Eyes – Paired; does not have eyelids Exterior of the Perch Nostrils – Paired; used to sense chemicals in the water; not connected to the throat Close up: Extended mouth Mouth – Specially adapted mouth that extends to form large gape (wide opening); the mouth is then quickly retracted resulting in a suction drawing prey into the mouth Eyes – Paired; does not have eyelids Click

Exterior of the Perch Click Lateral Line – Specialized sensory structure for detecting pressure changes/movement (Ex. vibration (waves) from movement of prey) Close up: Operculum and Gills Operculum - Bony flap that covers and protects the gills; opens and closes to help move (pump) water from the throat, across the gills, and then out the operculum Click

Exterior of the Perch Click Close up: Cloaca Close up: Scale on probe Scales - Very thin protective layer, almost transparent; made of bone like material and lie underneath a layer of skin (epidermis) Cloaca – Common opening for both the urogenital and digestion systems Click

Dissection 101: Perch Getting Started Use water to rinse the excess preservative from your specimen Click

Dissection 101: Perch 3 4 2 1 Click Lateral Line Operculum 3 4 2 1 Always cut away from yourself Place the scissors in the cloaca and press upward with lower part of the scissors against the muscle/skin to prevent cutting too deep; 1. cut toward the lateral line until you feel resistance from the upper cavity; 2. cut toward the head until you reach the operculum; 3. cut toward the head until you reach the operculum; 4. cut upward toward the lateral line; carefully remove the flap of muscle/skin to expose the body cavity (example next slide) Click

Dissection 101: Perch Click Swim bladder – Large adjustable air-filled sac-like structure that changes the density of bony fish (Osteichthyes) resulting in increased buoyancy (not found in sharks) The large structure shown above is the female gonad (ovary); depending on the season, the male and female gonads may be very large occupying most of the cavity, compressing other structures Click

Gonads – Reproductive structures Dissection 101: Perch Female or Male Things to look for: Single gonad in female (ovary); paired gonads in male (testes) The testes have a smooth, glandular appearance The ovary has a granular appearance (many developing eggs) Female Ovary Gonads – Reproductive structures Ovaries Developing eggs Ovary Female External Fertilization: Female lays eggs externally; male spreads gametes (sperm) over them; poor survival rate so many eggs and sperm released Testes Male Testis It is very difficult to distinguish female/male from the exterior of the perch; depending on the reproductive age/season, it may also be difficult to identify male or female internally. Click

scientifically smaller Dissection 101: Perch Slowly remove the gonad(s) with a probe; single female ovary shown in this example is very large, compressing other structures in the cavity; depending on the age of your specimen and season the gonad(s) could be scientifically smaller Click

Dissection 101: Perch Click The next two cuts (above) will help expose the structures compressed cranial by the large ovary; also the gills and heart will be visible; be careful not to damage the gills or heart. Click

Dissection 101: Perch Structure identification: Your specimen is unique; many of the structures will not look exactly like the photos or drawings in your book; the following slides will identify structures using multiple views and specimens Click

Color of a typical liver in a preserved perch Dissection 101: Perch Color of a typical liver in a preserved perch Liver (green in this specimen) – The liver is large, has a waxy appearance, and is usually white/tan; detoxifies blood and produces bile for fat digestion Click

Dissection 101: Perch Click Atrium (thin walled) – Receives deoxidated blood from the body and pumps it into the ventricle Spleen – Immune (white blood cell production); filters and stores blood Heart Ventricle – Muscular structure that pumps blood to the gills for oxygen exchange and then to the rest of the body Intestine – Digestion of food and absorption of nutrients (small section); movement of undigested waste to the anus (large section) Pyloric caeca – food storage and digestion Stomach – Muscular structure that mixes and stores food; food broken down by digestive juices Click

Dissection 101: Perch Click Liver Gills: Feather-like structures (increased surface area); used to remove oxygen from water for respiration Heart Click

Dissection 101: Perch Click Different Specimen Swim bladder Spleen Testis Liver Gills Heart Ruptured Intestine Intestine Click

Dissection 101: Perch Click Different Specimen Swim bladder Stomach Spleen Ovary Liver Intestine Click

Dissection 101: Perch Click Different Specimen Swim bladder Intestine Liver Heart Pancreas – Enzyme producing structure for digestion; insulin production Testis Click

Dissection 101: Perch Produced by Dakota State University and South Dakota Public Broadcasting Science Steve Sponsors