Therapeutic Treatment for Epibiotic Fouling on Dungeness Crab (Cancer magister) Larvae Reared in the Laboratory

Abstract

Larvae of the Dungeness crab (C. magister Dana) reared in the laboratory are susceptible to epibiotic microbial infestation similar to that described for eggs of the same species. Larval survival in the laboratory was increased by increased additions of antibiotics to the sea water: the chemotherapeutic agent, malachite green, was unsuccessful due to its toxicity to the sensitive larval stages. The addition of the diatom Phaeodactylum tricornutum was beneficial to larval survival in the light but detrimental in dark conditions, supporting the suggestion of a photosynthetic excretion from the algae capable of antibiotic activity. Chronic antibiotic treatment reduced the size of the larvae. Demonstration of larval susceptibility to epibiotic microbial infestation in the laboratory coupled with its occurrence on egg stages in nature provides reasonable evidence that the disease can occur on larval stages in nature.