Digestive System

The dissection of the crayfish requires a great deal of care.  Be certain to follow instructions carefully and to ask for assistance if you are in doubt about any part of the procedure. 

Position the crayfish dorsal side up.  Using a pair of scissors, remove the carapace from the cephalothorax by cutting along the mid-dorsal line. Make the incision and the posterior end of the carapace and cut up to the rostrum.  Carefully cut the carapace away along the side; do not disturb any of the underlying organs.  Locate the large yellowish digestive gland, which occupies much of the posterior part of the cephalothorax (Figure 13, 14). It secretes enzymes and stores food. With a probe, move it aside and find the remainder of the digestive system. The mouth (not visible at this time) leads via a short esophagus to the large stomach which occupies most of the anterior region of the cephalothorax.  Open the stomach and locate the chitinous teeth that form the gastric mill which is used to grind food.  The intestine runs from the stomach through the abdomen ending at the anus. 

Figure 13: Internal organs of the crayfish (lateral view). Note that the gills have been removed.

Figure 14: Pictures of the internal organs of the crayfish.