Weak or soft parts found on an otherwise apparently healthy lobster's shell is often indicative of shell disease. Shell disease is caused by microorganisms that consume chitin in the shell.

Lobsters with mild cases of shell disease often have a characteristic tunneling and pitting of the shell. The lobster shell is made up of dead tissue. Therefore, if a pathogen attacks the shell it doesn't necessarily "touch" the living lobster.

Lobsters with mild cases of shell disease can often escape the malady by shedding the microorganisms along with the attacked shell. Small lobsters molt frequently and are consequently more apt to escape dire cases of shell disease than are larger lobsters that molt less frequently. In extreme cases, shell disease results in ulceration's eating through the shell.

If shell disease attacks the area over the gills, the lobster is especially likely to die due to respiratory failure. A lobster's gills are located along its sides directly under the body shield and are attached to the legs. When you pull a leg off of a lobster to eat it, the gill often comes with it. Lobster gills appear grayish in color, have a rough texture, and a pungent taste. The unpleasant flavor comes from the nitrogenous wastes that are excreted across the gills.

If you are storing lobsters and you receive a shipment that contains lobsters that you suspect may have shell disease:

• Quarantine lobster with shell disease so that the microorganisms won't infest healthy lobsters.
• Allow lobsters with shell disease to shed if they appear to be close to molting.
• Immediately cook and process lobsters that you suspect may have shell disease.
• Try to determine where the lobsters were captured and report the occurrence of the disease to the marine resources agency in your state.