I.) External Anatomy
1. Place the preserved crayfish in a dissecting tray.
2. Note that the body of the crayfish is divided into three parts, the head, the cephalothorax and the abdomen.
3. Head - Identify the compound eyes on the rostrum portion of the head.
4. Cephalothorax - Find the Carapace, the covering of the cephalothorax region.
5. Note the larger antennae and smaller antennules protruding from the rostrum.
6. On the ventral side, locate the mouth with the mandibles, or true jaws. The mandibles tear the food, and the other appendages detect and hold food during feeding.
7. There are five pairs of walking legs connected ventrally to the carapace region. The first walking leg has enlarged pincers called chelipeds, and is used to manipulate objects and capture and crush food.
8. Abdomen - This section is a segmented tail. On the ventral side there are numerous swimmerets. The first pair is modified for the transfer of sperm in those that are ready to mate. Identify the uropod and the telson at the posterior end of the abdomen.
1. The gills are located on the outside of the body cavity in a space between the body wall and the carapace. Remove a segment of the carapace on one side of the crayfish to expose them.
2. Detach one of the walking legs, and note the small gill that is attached to the leg.
Enter content here
1. Locate a pair of nerves leading from the ventral nerve cord around the esophagus to the large ganglion, or brain, in the head. Short nerves connect the eyes, antennae, and antennules to the brain.
1. Locate the diamond shaped heart of the open circulatory system. The heart sends blood into the spaces around the organs through several arteries. After passing through the gills, the blood drains back into the heart through the openings (ostia) in it.
Digestive and Excretory Systems
1. Trace the digestive system from the mouth through the esophagus to the cardiac stomach, where the food is ground up.
2. From the stomach, food travels to the intestine, where it is absorbed into the blood stream.
3. Next, food waste is expelled through the anus.
4. Find the green gland located internally just behind each antenna and right under the brain. These structures filter fluid waste from the blood.
1. Remove the heart in order to see the gonads (reproductive organs; in males, the testes.) Locate the testes in the male crayfish. Be cautious when trying to find them because they are extremely small.
1. Locate the creamy - yellow ovaries in the female crayfish.