SQUID DISSECTION LAB INTRODUCTION OBJECTIVES MATERIALS

Transcription

1 SQUID DISSECTION LAB INTRODUCTION The cephalopods include squid, octopus, cuttlefish, and nautilus. The class name, Cephalopoda means head-foot.the foot in this group has adapted into arms, which are attached directly to the head. Most cephalopods do not have external shells. The squid has an internal remnant of a shell called a pen. Most cephalopods are relatively small. The giant squid, the largest of invertebrates, reaches lengths of 15m. It is the favorite prey of sperm whales and the basis for many mythes about sea monsters. OBJECTIVES - Examine members of the Phylum Mollusca describing structural characteristics that unify them. - Locate and identify major external and internal features and organs of a squid - Understand and use basic dissection techniques and terms - Critically examine the functions of several squid features and organs - Demonstrate proper techniques and respect for handling and disposing lab materials involving preserved specimens - Demonstrate safe and correct dissection techniques - Demonstrate ethical, responsible, co-operative behavior MATERIALS - Squid - Dissection Tray - Scissors - Pins - Probe - Forceps - Paper Towels - Water Bottle - Gloves

2 PROCEDURE Part I: External Anatomy 1. Place the squid with the dorsal (back) side up down the dissecting pan. Make sure the tentacles and arms are towards you. Spread out the arms, tentacles, and fins. 2. Locate and label the anterior/posterior, ventral/dorsal, head, eyes, arms (8), two longer feeding tentacles, fins, mantle, and siphon on the diagram in OBSERVATIONS. 3. Examine the suckers on the tentacles and arms as well as the spots on the skin, which are chromatophores. These freckles allow the squid to change colours. These spots change size to change the squid s colour for camouflage. Try rubbing them to see if you can see a change. Part II: Feeding 1. Locate the beak in the centre of the mouth. Open and close the beaks, noting how the ventral (front/ bottom) beak overlaps the dorsal (back/top) beak. 2. Use forceps, remove the beaks and place beaks together with dark pointed parts opposite one another. 3. Remove the radula (a ribbon with rows of teeth on a tongue-like muscle) from inside the mouth. In order to do so, make small incisions in the edge of the mouth. With forceps, locate the small, folded, plastic-like radula between beaks and remove it. Part III: Internal Anatomy 1. Keep the squid on its back. Using forceps, lift up the opening to the mantle and separate the mantle from the internal organs. 2. Cut along the ventral midline of the mantle, from its opening all the way to the tail. Be careful to keep the scissors lifted away from the internal organs as they are damaged. 3. Lay the flaps of mantle to the sides. 4. Draw and label the internal anatomy of the squid in your OBSERVATIONS. Part III: Systems 1. Find and label the gills (long, feather-shaped organs that are attached to the sides of the mantle). 2. Identify/label the gill hearts, one on the posterior end of each gill (small, flat and white).

3 3. Locate and label the squid s third heart (systemic heart), which pumps blood to the rest of the body. 4. Locate the stomach and cecum. If you see a long, silvery dark tube, do not break it because it is the ink sac. The stomach and cecum lie together as one white, silky digestive ducts for the squid. 5. Look for the creamy white brain between the eyeballs. Additionally determine the gender of your specimen. OPTIONAL - Open up the stomach and examine its contents. Many squid will have bits of partially digested crustaceans (pink and white pieces), or tiny fish scales and bones. Part IV: Ink Challenge 1. Locate the pen (gladius) of the squid, the long feather-shaped structure used to support the mantle and for organ attachment. 2. It and the cranium (brain case) make up the skeleton of the squid. It feels like plastic and is made of tissue similar to a shrimp shell. 3. The pen is revealed, lying along the dorsal midline of the mantle To remove the pen from inside the open mantle, grasp the head and organs firmly, and rotate them to the side with your left hand while holding on to one side of the mantle with your right hand and pulling away gently. 5. Pulling the pen out is similar to removing a splinter from your skin. You may need to cut away some connective tissue Locate the ink sac that lies connected to the intestines. 7. Use forceps to pierce/cut open the ink sac. 8. Dip the pointed tip of the pen in the squid ink, filling the tip with the dark fluid. 9. Using dipped pen, write your name to your diagram below. If the ink is dry and pasty, add 1 drop of water to create fluidity. (Though this may seem like a n unusual way to write, squid ink was used to write and draw in ancient times. Unfortunately, it tends to fade over time, except from your clothes!!!! BE CAREFUL!)

4 OBSERVATION Draw and/or label the external and internal anatomy of the squid. Squid External Anatomy Squid Internal Anatomy

5 DISCUSSION QUESTIONS 1. Kingdom: Phylum: Class: 2. What is the latin meaning of the phylum and class? 3. What happens when you rub the chromatophores? What advantages do cephalopods get from their chromatophores? 4. Identify the differences between the tentacles and the arms. Why are they different? 5. How does the squid obtain oxygen from the water? 6. What is the gender of your specimen? What structure of your squid specimen indicates its gender? 7. Why are the gill hearts white and our hearts are red or purple? The squid has a third heart (the systemic heart) that pumps blood to the rest of the body. 8. Describe 2 methods of escape (defence mechanisms) used by cephalopods. Give detailed answers.

6 9. What role does the squid play in the ocean ecosystem? 10. What adaptations does the squid have that allow it to play that role? 11. Describe the function of each of the following parts: STRUCTURE FUNCTION Fin Chromatophores Eye Arms and Tentacles Suction cups Pen Mantle Heart Gills Ink Sac Siphon