Name: 18 18 Date: Phylum Arthropoda: Shrimp Dissection Purpose: To examine and become familiar with the defining characteristics of Arthropods and be able to relate Arthropod structures to their functions. Procedure: This lab has two components that can be done in any order. It is recommended that students complete the Prawn Dissection first to ensure that they do not run out of time. Part A: Arthropods on Display 1. Examine the various Arthropods on display around the classroom. Provide at least 4 characteristics common to all of them. (2 Marks) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ 2. In the chart below provide the common name, Arthropoda class (use your text) and one adaptation of a common Arthropod characteristic for three of the Arthropods on display. An example has been provided. (0.5 Marks Per Box) Common Name Mantis Shrimp Biology 11: Phylum Arthropoda Class Name Crustacea Adaptation Thickening of forelimb exoskeleton used to break through mollusk shells Page 1 Part B: Shrimp Biology, Useful and Interesting Facts -Shrimp are crustaceans belonging to the Order Decapoda. They are typically found in warm, tropical waters, although some species do live in cold water (even in the Arctic!). Shrimp are omnivorous and are themselves important prey species for other animals (such as humans). -The shrimp body is divided into two main parts: a) Cephalothorax, a segment including the head and thorax. This area is covered by one continuous section of exoskeleton that ends as a rostrum at the anterior end of the shrimp; b) Abdomen, lower portion of the shrimp containing the pleopods (swimmerets) and tail. -Shrimp have separate sexes and fertilization is external. Fertilization occurs as up to 4,000 eggs leave the female’s body, which then attach to the hairs of her pleopods and are carried for up to four months. Part C: Shrimp External Anatomy Directions: Follow the instructions below and complete the questions provided using your observations, class notes and textbook. 1. The rostrum shape is unique to each species of shrimp. Draw the shape of your shrimp’s rostrum in the space below. (1 Mark) Notes: __________________________________________ __________________________________________ _________________________________________ __________________________________________ __________________________________________ 2. a) Shrimp have stalked eyes. Why would this be considered an advantage? (1 Mark) _____________________________________________________________________________________ _____________________________________________________________________________________ b) Carefully remove one of your shrimp’s eyes and examine it under a dissecting microscope. -Is the eye a single structure (like the squid’s) or is it made up of units? (1Mark) ____________________ c) Using your scissors, cut off a small portion of the eye. Place it in a drop of water on a glass slide and observe it under low power using a light microscope. Biology 11: Phylum Arthropoda Page 2 -What is the shape of the units? (1 Mark) ___________________________________________________ -Each of these units are called an ommatidium and they collectively make up the compound eye of Arthropods. 3. Examine the appendages found on the Cephalothorax. In Arthropods, appendages have been specialized to perform different tasks. Name at least three tasks performed by the legs on the Cephalothorax. (3 Marks) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ 4. Examine the appendages found on the Abdomen called the pleopods or “swimmerets”. What are two of their functions? (2 Marks) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ 5. Check out Shrimp feeding at http://www.arkive.org/common-prawn/palaemon-serratus/video-08b.html Biology 11: Phylum Arthropoda Page 3 Part D: Shrimp Internal Anatomy Biology 11: Phylum Arthropoda Page 4 Directions: Follow the instructions below to the best of your ability, ticking off which components you were able to complete in the right-hand boxes. Use the illustrations of the Shrimp and Crayfish internal anatomy at the back of the package to assist in you in this. 1. Place the specimen in the dissecting tray dorsal side up. 2. Carefully insert the point of the scissors under the top of the carapace (shell) at the back of the cephalothorax and cut up the middle to the rostrum. 3. Cut across the carapace just back behind the eyes and remove the two pieces of the carapace. 4. Note the exposed gills. (Feathery like structures just under the carapace you just remove) 5. Remove the exposed gills and legs attached to the thorax. Carefully separate the dorsal layer of muscles in the thorax and note the light colored heart just underneath. 6. Remove the heart. The two light colored masses extending on each side of the body into the head are the digestive glands. (The heart is located just posterior to these.) 7. Between the digestive glands, you will find the small pair of white reproductive organs in the male animal. If your specimen is female, you will probably see a large mass of dark colored eggs. 8. To locate the intestine, insert the point of the scissors under the dorsal side of the shell of the abdomen and cut back to the telson. Spread the shell, and the intestine will be found as a tube on the tops side of the muscles of the abdomen. 9. Trace it forward to the point where the intestine joins the large, thin walled stomach in the front part of the cephalothorax. 10. Now, remove all the organs in the thorax by cutting the short esophagus below the stomach and the bands of muscle holding the stomach just back of the eyes. You should be able to lift out most of the internal organs in one piece. 11. Clean out the remaining tissue in the head so that the green glands (kidneys) are exposed. 12. In the front part of the head cavity, between the eyes, not the small mass of white tissue, the brain. 13. Trace the nerves that go from the brain to the antennae and eyes. 14. Cut the hard tissue on the floor of the thorax with your scalpel so that you can follow the ventral nerve cord back from the brain to the abdomen. 15. Spread the shell of the abdomen apart and pull out the large muscle. (This is the part of the body eaten in shrimp and lobsters) 16. Note the nerve cord that is now exposed on the floor of the abdomen. The enlargements of the nerve cord in each segment of the abdomen are the ganglia. Biology 11: Phylum Arthropoda Page 5 Conclusion 1. Research the ecology of shrimp. What roles do they play in their environments? (2 Marks) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ Biology 11: Phylum Arthropoda Page 6
