Crayfish Dissection
Background
The crayfish is typical of most shrimplike crustaceans and is characterized by a joined head and thorax, or midsection, and a segmented body. Crayfish are usually about 7.5 cm (3 inches) long. The head has two pairs of sensory antennae and a pair of eyes on movable stalks. The appendages of the thorax include four pairs of walking legs which, as well as walking, are to probe cracks and crevices between rocks looking for food. Crayfish also have one pair of chelipeds, which it extends in front of its body while moving. These strong pinchers are specialized for cutting, capturing food, attack, and defense. They have swimmerets that are used for swimming and for reproduction. Crayfish have a hard outside skeleton. This jointed exoskeleton provides protection and allows movement. As a result, the crayfish regularly gets too big for its skeleton, sheds it, and grows a new larger one. This is called molting. Crayfish belong to the Class Crustacean and the Phylum Arthropoda. Arthropods are classified based on the structures of their segments, types of appendages, and mouthparts.
Objectives
-compare and contrast the internal and external anatomy of the crayfish
-analyze the structure of anatomical parts to their functions
-identify the internal and external anatomy of the crayfish
Figure 1
KNOW: What do you know about the crayfish?
Objectives
-identify crayfish anatomy
-describe crayfish anatomical structures and tell why they contribute to the survival of the crayfish
Materials
Preserved crayfish, dissecting tray, dissecting tools, googles, protective gloves
Fluids that preserve organisms will burn your eyes!
Procedure
1.Obtain a crayfish and identify the external anatomical parts located in figure 1.
2.Use scissors to cut through the back of the carapace on the along the top toward the middle. Use forceps to pull the carapace off being careful not to pull of any internal organs. You may need to cut along the carapace toward the bottom to be able to fully remove it. Pull the rostrom up to expose all of the internal organs. Identify all of the anatomical organs located in figure 2 and figure 3.
Figure 2
Figure 3
3.Locate the telson. Carefully pull of the segements exposing the fleshy part of the crayfish that you would eat. Identify the anatomical organs located in figure 4.
Figure 4
WHAT: What did you learn about the crayfish?
Answer five analysis questions using complete sentences.
1.Why is the feathery appearance of the gills important to the survival of the crayfish?
2.How is the structure of the cheliped important to the survival of the crayfish?
3.Is the crayfish most vulnerable to its enemies from the dorsal or ventral side AND why?
4.In relation to motion, what is the function of the telson?
5.What is the function of the mandibles?
6.Why would the crayfish want to hide right after it molts?
LEARN: What do you still want to learn about the crayfish?