Download Dissection Lab I (week 2)

Insect Physiology (Ento 306) Name:______________________ Insect Dissection Labs Part 1 Introduction This lab is designed to allow you the student to become comfortable with dissection and internal anatomy of the dominant life form on earth…insects. These skills will be necessary for completing future labs and are vital if you will be working as a biologist. This lab handout provides you with the basic instructions for dissection and an outline of the tissues, organs, and structures that you will need to be familiar with and in some cases draw. All questions you need to ask or things you need to draw are underlined. You will make all your drawings, which must include a short description and magnification used, in the drawing handout. Make use of the appendix, which is a collection of diagrams from textbooks, websites, and literature that will be helpful in finding the correct structures and organs. Please feel free to ‘explore’. If you would like to dissect any additional parts and observe them under the stereoscope or compound microscope go ahead! Supplies Saline Solution (0.9 NaCl w/v which is 9g NaCl per 1000mL H2O) Dissection probes (produce your own using a wood dowel and insect pin) Forceps Scissors Razor blade Insect/dissection pins Dissection tray Freshly sacrificed American bird grasshopper (Schistocerca americana) Microscope slides and cover slips Eye dropper Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) Metabolic/Excretory systems Grasshopper alimentary canal Using the scissors or razorblade carefully cut the last segment of the abdomen. Next, gently pull the head off so that the attached gut is withdrawn. You should have an intact whole gut now. Place the gut in your dissecting tray, and wash it with some saline solution. Identify the following structures: Foregut Esophagus Crop Midgut Gastric caeca Midgut Hindgut Malphigian tubules Ileum Colon Rectum Remove the head by cutting through the esophagus (don’t toss the head, you will need it later). Now using your scissors cut lengthwise down one side of the gut. 1) Identify and draw the proventriculus. Observe what the lining of the foregut, midgut, and hindgut look like under the stereoscope. Cut out a small section of gastric caeca and 2) draw the surface as seen under the compound microscope. Mouthparts On the head, identify and pull out the following mouthparts using your forceps: Labrum Mandible Maxilla Maxillary palp Hypopharynx Labium Labial palp 3) Draw the chewing edge of the mandible as viewed under a stereoscope. Nervous systems Mechanoreceptors/chemoreceptors Remove the distal (tip) segments of an antenna, a maxillary or labial palp, and the front tarsus (the foot of the grasshopper). Place them on a microscope slide with a cover slip (this is called a dry mount). Place the tarsus with the plantar surface (underside) visible. Observe these body parts under the compound microscope. The long narrow hairs or trichoid sensillum are mechanoreceptors and allow insects to sense whether or not they are in contact with something such as a leaf, mate, or the mouth of a predator! Shorter stubbier hairs are chemoreceptors and allow the insect to smell and taste. 4) and 5) Draw two of these three body parts (antenna, palp, or tarsus) and label the sensillum visible. Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) Compound eyes and ocelli Identify the compound eyes and simple ocelli using the stereoscope. Slice off the surface of one of the compound eyes with a razor blade and view a section of the compound eye under the compound microscope. 6) Draw it and label the ommatidia. Tympanum Hold back or cut off the wings on one side of the grasshopper and locate the tympanum. This organ is used by the grasshopper for hearing. Not all insects have them and their location is highly variable. Respiratory systems Spiracles Identify a spiracle using the stereoscope. Insects breathe in oxygen using these structures which lead to an intricate internal system of tubes called trachea. Locomotor systems Remove one of the hind legs and identify the following: Tarsus (Pretarsus, tarsal claws, tarsomeres) Tibia Femur Trochanter Coxa (likely still attached to the grasshopper) Observe the leg joint between the femur and tibia under the stereoscope. Note the membrane connecting these leg segments. Using the razorblade carefully cut sagitally through the side of the hind femur as shown by your TA. 7) Draw the internal structure of the joint between the tibia and femur. Remove a small piece of muscle tissue and observe it under the compound microscope as a wet mount. Note the striated muscle tissue and the vein-­‐like trachea and tracheoles. These tubes deliver oxygen to the tissue. 8) Draw what you see. Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) Appendix Lateral view of an adult male lubber grasshopper Illustrations by Richard Fox (http://webs.lander.edu/rsfox/invertebrates/romalea.html) Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) Internal anatomy of the grasshopper (lateral view)
http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb6pg17.htm Internal anatomy of the grasshopper (lateral view)
Florida Center for Instructional Technology Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) Dorsal dissection of a male Romalea showing the digestive system.
The dorsal diaphragm and heart have been removed; most of the Malpighian tubules and most
of the epiproct have been removed. The few Malpighian tubules in the drawing are shown much
shorter and much less numerous than in life. The testis has been removed but its position is
indicated by a dashed line. The ovary occupies a similar position in females. Illustrations by Richard Fox (http://webs.lander.edu/rsfox/invertebrates/romalea.html) Diagrammatic cross section of a generalized insect abdominal segment
Redrawn from Snodgrass (1935) Illustrations by Richard Fox (http://webs.lander.edu/rsfox/invertebrates/romalea.html) En face view of Romalea Illustrations by Richard Fox (http://webs.lander.edu/rsfox/invertebrates/romalea.html) Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) External anatomy of the grasshopper head (lateral view)
http://basicentomology.ifas.ufl.edu Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) Disarticulated mouthparts of a chewing insect
http://basicentomology.ifas.ufl.edu/lab5.doc Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) Structure of the insect compound eye in cross-section
http://www.biology-­‐resources.com/insects-­‐02.html cuticle
ommatidium
nerve fibres
Structure of the ommatidia in expanded lateral view http://www.biology-­‐resources.com/insects-­‐02.html cuticular
lens
crystalline
cone (lens)
matrix cell
(secretes
crystalline cone)
rhabdom
(transparent rod)
light-sensitive
cell
nerve fibre
Adapted from Paul A. Lenhart 2011 Insect Physiology (Ento 306) The insect leg
http://basicentomology.ifas.ufl.edu Muscles of the hind leg of a snow fly, Chionea alexandriana, drawn by Dr. George Byers.
Each numbered muscle has a base, or "origin," and an "insertion" point where it is
attached and moves when the muscle shortens. Adapted from Paul A. Lenhart 2011