Lab Studies Treatment of Shell Disease

by Laurie Schreiber

PORTLAND—The treatment of shell disease in a lab setting could help maintain the health and appearance of lobsters for exhibition purposes. But it’s unclear how the process for individual lobsters can help with the prevention of shell disease in the wild.

Anita Kim, the lobster hatchery manager at the New England Aquarium in Boston, gave a presentation on lab experiments at the 11th annual conference on lobster biology and management, held June 4-9 in Portland.

Kim has been rearing lobsters and monitoring them on a regular basis, leading to studies on a laboratory-model of shell disease in hatchery-raised juvenile lobsters. This form of shell disease is similar to that seen in lobsters held in captivity for exhibit purposes, she said. A common concern for exhibits is the aesthetics of the animals,

and crustaceans exhibiting shell disease symptoms are often removed. Animal care staff have had a growing need to be able to treat crustaceans in their care to prevent or slow shell disease symptoms.

Most aquariums run semi-closed recirculation programs, resulting in some kinds of diseases no matter how much the water is filtered, Kim said.

“We get calls from other aquariums—‘My crab, lobster, shrimp keep getting brown spots on their shell. What can we do about that?’” she said.

Shell disease occurs on many types of crustaceans, and the treatment to date has been to wait for the animal to molt—not the best answer when talking with animal care programs that want to put the animal on display, she said.

Waiting for a lobster to molt can take weeks or even months, depending on the size of the animal, she said.

“So we’re hoping to find something that’s more proactive in dealing with shell disease within these exhibits,” she said.

The experiments included various treatments to see if shell disease could be prevented from occurring, and to treat existing disease lesions or modes of entry such as a wounded shell. The experiments included parameters such as short-term duration, with the idea of removing animals from an exhibit for only a short period of time. And it should be safe, so that it could performed repeatedly.

Topic applications included a freshwater rinse, to remove saltwater microbess on the shell; vitamin E oil; and Betadine.

Other treatments included a bath in Formalin, a common aquatic anti-microbial and anti-fungal treatment; and Malachite Green, an anti-fungal agent. Better results were seen with Formalin and Malachite Green, she said. The freshwater treatment had the worst outcome.

Kim said she plans to continue the experiments, and will also look at stress response and its relation to shell disease.

Lab-based model shell diseases are not considered to be the same as epizootic shell disease that occurs in the wild, she said. Epizootic shell disease is caused by a bacteria that eats away at outer shells, can cause increased mortality in lobster populations, and decreases in reproductive success and market value.