Classification of Homarus americanus hemocytes and the use of differential hemocyte counts in lobsters infected with Aerococcus viridans var. homari (Gaffkemia)

Hemocytes of the American lobster ( Homarus americanus H. Milne Edwards) were classified after examination of Wright–Giemsa stained cytocentrifuge preparations by brightfield light microscopy. Eleven hemocyte types were identified using morphologic criteria. The classification system was then used to monitor changes in the differential hemocyte count (DHC) of lobsters infected with the Gram positive coccus Aerococcus viridans var. homari, etiologic agent of gaffkemia. The appearance of less mature hemocytes in the DHCs of lobsters in the late stages of infection was similar to the ‘left shift’ of vertebrate inflammation. Results from this study suggest that DHCs can be used to assess and characterize inflammation in H. americanus and possibly other crustaceans.