Phagocytosis constitutes the primary defense mechanism in decapod crustaceans. In this study, monolayers of hemocytes of the American lobster, Homarus americanus , were allowed to phagocytize a strain of Aerococcus viridans . This system was used to investigate the effects of temperature on in vitro phagocytosis. The results indicated a marked decrease in percent phagocytosis at 22°C and above. As this primary response was rendered less efficient at higher temperatures, culture of Homarus americanus at elevated temperatures was cautioned.

Six microbial diseases of cultured American lobsters (Homarus americanus) determined to be of significant concern to commercial aquaculture are discussed in relation to present knowledge of characteristics of the causative microorganisms, lobster susceptibility, environmental influence, severity, gross and microscopic recognition, physiological changes, contagion and control. The diseases reviewed here include shell disease, Gaffkemia, microbial epibiont disease, Lagenidium disease, Haliphthoros disease, and Fusarium disease.

Virulent strains of Aerococcus viridans (formerly Gaffkya homari) are the aetiologic agents of gaffkemia, a septicaemic disease of the American lobster (Homarus americanus). The virulent and avirulent forms of this bacterium, previously thought to be taxonomically indistinguishable, have been differentiated by serological studies. Antisera were produced in rabbits using autoclaved bacteria as antigens. Reactions were measured by agglutination tests using microtitre techniques and an antigenic scheme was determined. Specific antisera were prepared by absorption and used to determine antigens of strains of A. viridans and other Gram-positive cocci. In general, only virulent strains of A. viridans have antigen b. Both virulent and avirulent strains possess other antigens also detected in strains of the genus Staphylococcus.

Virulent Pediococcus homari, the etiological agent of gaffkemia, a disease enzootic in Atlantic lobsters (genus Homarus), was isolated from two sites in Anaheim Bay, Calif. The concentration of P. homari was in the order of 1–10 bacteria per ml of sample. This is the first known report of free-living P. homari in the Pacific; the bacterium was previously reported to exist in infected decapod Crustaceae and sediments from the Atlantic. Introduction of P. homari may have occurred through transport of infected Homarus americanus (Atlantic lobster), or by discharge of water in contact with them.

Torulopsis homii and several other yeasts grew well in a synthetic medium containing 1.0 μmolar zinc. Additional zinc increased neither the growth rate nor total growth. In concentrations up to 10 μmolar, essentially 100% of the zinc added to a culture of T. homii was accumulated during growth by the cells; soon after reaching the stationary phase, most of the metal was eliminated into the medium in the ionic state. The release of zinc was correlated with the lowering of the pH of the medium by the fermentation products.In contrast to the lack of effect on growth, the concentration of zinc markedly influenced the viability of yeast cultures. The presence of 10 to 100 μmolar zinc at the time of inoculation greatly increased the death rate of stationary phase cultures. Likewise, subfungistatic concentrations of cadmium or copper, but not iron or manganese, decreased culture longevity. This action of zinc, cadmium, and copper is attributed to the ability of these metals to suppress fungal secondary metabolism.