Crawdad Dissection Instructions

Use this site to guide you in your identifying organs in your crayfish today.

1. Put on safety goggles. You may use gloves if you want.

2. Using one hand to hold the crayfish dorsal side up in the dissecting tray, use scissors to carefully cut through the back of the carapace along dissection cut line 1, as shown in the diagram below. Cut along the indentations that separate the thoracic portion of the carapace into three regions. Start the cut at the posterior edges of the carapace, and extend it along both sides in the cephalic region.

CrayfishTopView.jpg3. Use forceps to carefully lift away the carapace. Be careful not to pull the carapace away too quickly. Such action would disturb or tear the underlying structures.
4. Place the specimen on its side, with the head facing left, as shown in the diagram below. Using scissors, start cutting at the base of cut line 1. Cut along the side of the crayfish, as illustrated by cut line 2. Extend the cut line forward toward the rostrum (at the top of the head).


5. Use forceps to carefully lift away the remaining parts of the carapace, exposing the underlying gills and other organs.
6. Use the diagram below to locate and identify the organs of the digestive system. Locate the maxillae that pass the pieces of food into the mouth. The food travels down the short esophagus into the stomach. Locate the digestive gland, which produces digestive substances and from which the absorption of nutrients occurs. Undigested material passes into theintestine. Observe that the intestine is attached to the lobed stomach. The undigested material is eliminated from the anus.


external image bd14752_.gifRows of chitinous teeth line the stomach. Predict their function.

7. Use the diagram below to locate and identify the organs of the respiratory system. Locate the gills, which are featherlike structures found underneath the carapace and attached to the chelipeds and walking legs. A constant flow of blood to the gills releases carbon dioxide and picks up oxygen.


external image bd14752_.gifThe feathery nature of the gills gives them a very large surface area. Why is this important?

8. Use the diagram of the internal anatomy of the crayfish to locate and identify the organs of the circulatory system. Locate the dorsal tubular heart and several arteries. The crayfish has an open circulatory system in which the blood flows from arteries into sinuses, or spaces, in tissues. The blood flows over the gills before returning to the heart.


9. Use the same diagram to locate and identify the organs of the nervous system. Find the ventral nerve cord. Locate a ganglion, one of the enlargements of the ventral nerve cord. Locate the dorsal brain, which is located just behind the compound eyes. Note the two large nerves that lead from the brain, around the esophagus, and join the ventral nerve cord.

external image bd14752_.gifMany nerves leave from each ganglion. Where do you think these nerves go?

10. Use the same diagram to locate and identify the organs of the excretory system. The blood carries cellular wastes to the disk-like green glands. Locate these organs just in front of the stomach. The green glands excrete waste through pores at the base of each antenna.

external image bd14752_.gifWhat organs in your body carry out the same function as the green glands?


Grasshopper Instructions

This link will guide you in identifying grasshopper organs today.

This link will be helpful as well

(from Carolina Biological)

    1. Place the specimen in the dissecting pan ventral side up. Use scissors to cut through the exoskeleton’s ventral side from the head to the posterior end of the abdomen.
    2. Pull the cut sides apart and observe the tracheal tubes running into the internal organs. Pin each side of the insect to the dissecting pan.
    3. Locate the yellow fatty tissue that covers the internal organs. Carefully remove this layer with forceps to observe the organs. Refer to the drawing below to locate the structures discussed in the following steps.
external image grasshopper_internal.jpg
  1. Locate the digestive system. The crop, found at the anterior portion of the digestive tract, is an organ for storing food. The gastric cecae, or digestive glands, are attached to the stomach.
  2. Identify the reproductive organs that lie on either side of the abdominal digestive organs. In a female, the ovary appears as a series of tubules containing rodlike eggs. Females also have ovipositors, 4 curved projections at the end of the abdomen. These are used to dig a hole for egg deposition. In males, the testis is a coiled cord containing many tubules. The posterior end of the male abdomen has claspers, which are used during reproduction.
  3. After you have completed the dissection, dispose of the specimen in accordance with local guidelines and your teacher’s instructions