After obtaining a live crab, freeze at -20ºC for one hour to kill your specimen. Do not leave your specimen in the freezer longer than two hours as internal organs may begin to disintegrate. Rapid freezing with liquid nitrogen is also an option, but take note that it is necessary to allow minimal thawing prior to dissection as the carapace may freeze to the internal organs as a result of ice formation.
Determine if your crab is male or female. This is easily done by observing the telson folded under the ventral surface of the specimen. A female has a broad U-shaped telson, while a male has a narrow V-shaped telson. 
Begin the dissection by carefully removing the carapace. This can be done by using a scalpel to cut around the lateral edges, working from one side, posteriorly, and up the other side. The carapace can be opened as if on a hinge attached at the eye-stalks. Be careful when lifting the carapace, since the epidermis may adhere to the underside of the carapace. 
Remove the epidermis. The easiest way to do this is under a dissecting microscope using a pair of dissecting tweezers. Be careful when removing the epidermis since rapid removal tends to disturb the underlying hepatopancreas and stomach. 
The hepatopancreas, which can be orange or yellow and is the most extensive structure inside the crab, may be removed with tweezers. Once removed, this organ loses most of its structure and takes on an amorphous consistency. Note that if you are dissecting a male, the white worm-like testis are located ventral to the hepatopancreas and can easily be confused with epidermal or hepatopancreas tissue. If you are dissecting a female, the ovaries lie dorsal to the hepatopancreas.
st meal. Turn the stomach over and observe the denticles, which lie at the posterior portion of the organ. These have the appearance of a set of teeth. 
Finally, note the feather-like gills sitting dorsally on the muscle and posterior to the hepatopancreas. 
[Biology program] [Department of Earth and Biological Sciences homepage]
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Last Revised: Wed, Jun 07, 2006