Fish and Insect Dissection

• Dissections are a vital part of scientific research
• Dissections


  • They allow for the internal structures of organs to be examined so that theories can be made about how they function
• Ethical concerns surrounding dissections

  • People worry about how the animals for dissections are raised and killed
  • It goes against the religious beliefs of some individuals
• Biological specimen


  Should be from a reputable source and should be disposed of in the correct manner
• If multiple specimens are being dissected then they should be taken from individual organisms of the same species and roughly the same age
• Apparatus


  • Scissors
  • Scalpel
  • Tweezers / Forceps
• Method


  • Dissection board
  • Paper towels
  • Biological specimen
  • Pins
• A lab coat, gloves and eye protection should be worn to avoid contamination with biological material (which could cause an allergic reaction)
• Dissection procedure


  1. Place the specimen on the dissecting board

  2. Use the tools to access the desired structure

  3. When using the scalpel cut away from your body and keep your fingers far from the blade to reduce the chance of cutting yourself

  4. Scissors can be used for cutting large sections of tissue (cuts do not need to be precise)

  5. A scalpel enable finer, more precise cutting and needs to be sharp to ensure this

  6. Use pins to move the other sections of the specimen aside to leave the desired structure exposed
• Limitations of dissection


  • It can be hard to see some of the smaller, finer structures within organs
  • The specimens do not reflect how the tissue would look in a living organism
  • If only a single specimen is dissected then anomalies found within that specimen may be ignored or glossed over
• The main structures of the gas exchange systems in mammals and fish can be revealed in dissections
• The much smaller gas exchange systems of organisms such as insects can be more difficult to examine by dissection
• Mammalian lungs


  • Trachea
  • Bronchi
  • Bronchioles
• The smaller structures such as the alveoli can be hard to distinguish in a dissected lung
• Bony fish gills


  • Gill arch
  • Filaments
• The smaller structures such as the lamellae can be hard to distinguish in a dissected fish
• Insect tracheal system


  • Requires specialised equipment and skills
  • Microscopes are also needed to observe the structures
• The gas exchange surfaces of different organisms can be observed using microscopes
• They often appear very different in photomicrographs than they do in the diagrams found in textbooks
• It is important to be able to identify the gas exchange surface and the key structures present
• Mammal gas exchange


  • Alveoli are of different sizes and shapes
  • Nuclei are shown as dark dots
  • Blood vessels can found in between the alveoli
  • Sometimes white blood cells are present in tissue samples
• Fish gas exchange


  • Gill arch resembles a backbone for the gills
  • The different filaments are shown with many of the lamellae visible
• Insect gas exchange


  • Electron microscopes can take clear images of the spiracle structures found on the surface of insects